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All questions of Chemical Reactions and Equations for Class 10 Exam
A balanced chemical equation is in accordance with which one of the following laws given below- a)Law of constant proportion
- b)Law of conservation of energy
- c)Law of conservation of mass
- d)Low of multiple proportion
Correct answer is option 'C'. Can you explain this answer?
A balanced chemical equation is in accordance with which one of the following laws given below
a)
Law of constant proportion
b)
Law of conservation of energy
c)
Law of conservation of mass
d)
Low of multiple proportion
|
|
Maitri Daga answered |
Answer C
its absolutely correct
its absolutely correct
Which of the following is not a physical change ?- a)Boiling of water to give water vapour
- b)Melting of ice to give water
- c)Dissolution of salt in water
- d)Combustion of liquefied petroleum Gas (LPG)
Correct answer is option 'D'. Can you explain this answer?
Which of the following is not a physical change ?
a)
Boiling of water to give water vapour
b)
Melting of ice to give water
c)
Dissolution of salt in water
d)
Combustion of liquefied petroleum Gas (LPG)
|
Aarav agarwal answered |
Physical and Chemical Changes
Physical changes are reversible changes that do not involve a change in the chemical composition of a substance. Examples of physical changes include changes in state (solid, liquid, gas), changes in shape or size, and changes in color or texture. In contrast, chemical changes involve a change in the chemical composition of a substance, resulting in the formation of a new substance(s) with different properties.
Explanation
Of the given options, option 'D' - combustion of liquefied petroleum gas (LPG) is not a physical change. Combustion is a chemical change that involves the reaction of a fuel (LPG in this case) with oxygen in the air, producing heat and light energy. The products of the combustion of LPG are carbon dioxide and water vapor, which are different from the original fuel.
On the other hand, boiling of water to give water vapor, melting of ice to give water, and dissolution of salt in water are all physical changes. In these processes, no new substances are formed, and the original substance(s) retain their chemical composition.
Conclusion
In summary, physical changes are characterized by the absence of a chemical reaction, and the original substance(s) retain their chemical composition. Option 'D' is the correct answer as it represents combustion, which is a chemical change that involves the formation of new substances with different properties.
Physical changes are reversible changes that do not involve a change in the chemical composition of a substance. Examples of physical changes include changes in state (solid, liquid, gas), changes in shape or size, and changes in color or texture. In contrast, chemical changes involve a change in the chemical composition of a substance, resulting in the formation of a new substance(s) with different properties.
Explanation
Of the given options, option 'D' - combustion of liquefied petroleum gas (LPG) is not a physical change. Combustion is a chemical change that involves the reaction of a fuel (LPG in this case) with oxygen in the air, producing heat and light energy. The products of the combustion of LPG are carbon dioxide and water vapor, which are different from the original fuel.
On the other hand, boiling of water to give water vapor, melting of ice to give water, and dissolution of salt in water are all physical changes. In these processes, no new substances are formed, and the original substance(s) retain their chemical composition.
Conclusion
In summary, physical changes are characterized by the absence of a chemical reaction, and the original substance(s) retain their chemical composition. Option 'D' is the correct answer as it represents combustion, which is a chemical change that involves the formation of new substances with different properties.
A dilute ferrous sulphate solution was added to the beaker containing acidified permanganate solution. The light purple colour of the solution fades and finally disappears. Which of the following is the correct explanation for the observation?- a)KMnO4 is an oxidising agent, it oxidises FeSO4
- b)FeSO4 acts an oxidising agent and oxidises KMnO4
- c)KMnO4 is an unstable compound and decomposes in presence of FeSO4 to a colourless compound
- d)The colour disappears due to the dilution : no reaction is involved
Correct answer is option 'A'. Can you explain this answer?
A dilute ferrous sulphate solution was added to the beaker containing acidified permanganate solution. The light purple colour of the solution fades and finally disappears. Which of the following is the correct explanation for the observation?
a)
KMnO4 is an oxidising agent, it oxidises FeSO4
b)
FeSO4 acts an oxidising agent and oxidises KMnO4
c)
KMnO4 is an unstable compound and decomposes in presence of FeSO4 to a colourless compound
d)
The colour disappears due to the dilution : no reaction is involved
|
Priyanka Kapoor answered |
In this reaction, potassium permanganate (KMnO4) is an oxidizing agent. It oxidises ferrous sulphate to ferric sulphate in the presence of dilute H2SO4.
2KMNO4 + 10FeSO4 + 8H2SO4 → K2SO4 + 2MnSO4 + 5Fe(SO4)3 + 8H2O
The solution is coloured purple because of the KMnO4 and it eventually disappears when all the KMnO4 in the solution is utilized.
2KMNO4 + 10FeSO4 + 8H2SO4 → K2SO4 + 2MnSO4 + 5Fe(SO4)3 + 8H2O
The solution is coloured purple because of the KMnO4 and it eventually disappears when all the KMnO4 in the solution is utilized.
Which of the following gases can be used for storage of fresh sample of an oil for a long time?- a)Carbon dioxide or oxygen
- b)Carbon dioxide or helium
- c)Nitrogen or oxygen
- d)Nitrogen or helium
Correct answer is option 'D'. Can you explain this answer?
Which of the following gases can be used for storage of fresh sample of an oil for a long time?
a)
Carbon dioxide or oxygen
b)
Carbon dioxide or helium
c)
Nitrogen or oxygen
d)
Nitrogen or helium
|
Vidhi dubey answered |
Answer:
Introduction:
When storing a fresh sample of oil for a long time, it is important to prevent its degradation or oxidation. This can be achieved by using an appropriate gas to create an inert atmosphere that minimizes contact with oxygen, moisture, and other reactive substances. Among the options given, nitrogen or helium are the most suitable gases for this purpose.
Explanation:
Nitrogen:
- Nitrogen is an inert gas, meaning it is chemically unreactive and does not readily react with other substances.
- It is abundantly available in the atmosphere and is commonly used for various industrial and laboratory applications.
- When used for storing oil samples, nitrogen replaces the oxygen in the storage container, thus creating an oxygen-free environment.
- This prevents oxidation and slows down the degradation of the oil, helping to maintain its freshness and quality over a long period of time.
Helium:
- Helium is another inert gas that is chemically stable and does not react with other substances.
- It is lighter than air and has low solubility in most liquids, including oil.
- When used as a storage gas, helium creates a protective blanket over the oil sample, preventing oxygen and moisture from coming into contact with the oil.
- This helps to maintain the oil's freshness and prevents degradation or oxidation.
Comparison:
Both nitrogen and helium are suitable for storing oil samples for a long time. However, there are a few key differences between the two gases:
- Availability: Nitrogen is more readily available and less expensive compared to helium, which is relatively rare and more expensive.
- Density: Helium is lighter than air and has low solubility in oil, making it more effective in creating a protective blanket over the oil sample.
- Cost: Nitrogen is generally more cost-effective and practical for most applications. Helium is typically reserved for specialized or high-value samples due to its higher cost.
Conclusion:
In conclusion, nitrogen or helium can be used for the storage of fresh samples of oil for a long time. Both gases create an inert atmosphere that prevents oxidation and degradation of the oil. Nitrogen is more commonly used due to its availability and cost-effectiveness, while helium is preferred for specialized or high-value samples.
Introduction:
When storing a fresh sample of oil for a long time, it is important to prevent its degradation or oxidation. This can be achieved by using an appropriate gas to create an inert atmosphere that minimizes contact with oxygen, moisture, and other reactive substances. Among the options given, nitrogen or helium are the most suitable gases for this purpose.
Explanation:
Nitrogen:
- Nitrogen is an inert gas, meaning it is chemically unreactive and does not readily react with other substances.
- It is abundantly available in the atmosphere and is commonly used for various industrial and laboratory applications.
- When used for storing oil samples, nitrogen replaces the oxygen in the storage container, thus creating an oxygen-free environment.
- This prevents oxidation and slows down the degradation of the oil, helping to maintain its freshness and quality over a long period of time.
Helium:
- Helium is another inert gas that is chemically stable and does not react with other substances.
- It is lighter than air and has low solubility in most liquids, including oil.
- When used as a storage gas, helium creates a protective blanket over the oil sample, preventing oxygen and moisture from coming into contact with the oil.
- This helps to maintain the oil's freshness and prevents degradation or oxidation.
Comparison:
Both nitrogen and helium are suitable for storing oil samples for a long time. However, there are a few key differences between the two gases:
- Availability: Nitrogen is more readily available and less expensive compared to helium, which is relatively rare and more expensive.
- Density: Helium is lighter than air and has low solubility in oil, making it more effective in creating a protective blanket over the oil sample.
- Cost: Nitrogen is generally more cost-effective and practical for most applications. Helium is typically reserved for specialized or high-value samples due to its higher cost.
Conclusion:
In conclusion, nitrogen or helium can be used for the storage of fresh samples of oil for a long time. Both gases create an inert atmosphere that prevents oxidation and degradation of the oil. Nitrogen is more commonly used due to its availability and cost-effectiveness, while helium is preferred for specialized or high-value samples.
When a black and white photographic film is exposed to light, the grey colour on the photographic film is due to presence of- a)Ag2O
- b)Ag
- c)Br2
- d)All of these
Correct answer is option 'B'. Can you explain this answer?
When a black and white photographic film is exposed to light, the grey colour on the photographic film is due to presence of
a)
Ag2O
b)
Ag
c)
Br2
d)
All of these
|
|
Ritu Saxena answered |
A strip or sheet of transparent plastic film base is coated with gelatin emulsion containing small light sensitive silver halide crystals on one side. When the exposed silver halide grains are developed, they are converted to metallic silver which appears as the black part of the film due to blocking of light.
Therefore, the image on an exposed and developed photographic film is due to Ag.
Therefore, the image on an exposed and developed photographic film is due to Ag.
Which one of the following is not a chemical change?- a)Cooking of food
- b)Evaporation of water
- c)Burning of candle wax
- d)Digestion of food in our body
Correct answer is option 'B'. Can you explain this answer?
Which one of the following is not a chemical change?
a)
Cooking of food
b)
Evaporation of water
c)
Burning of candle wax
d)
Digestion of food in our body
|
|
Sarangi rao answered |
Chemical and Physical Changes
Chemical changes involve the formation of new substances with different chemical properties, while physical changes involve changes in the physical state or appearance of a substance without changing its chemical composition.
Cooking of Food
Cooking of food involves chemical changes, as the heat and other ingredients cause chemical reactions that alter the taste, texture, and nutritional value of the food.
Evaporation of Water
Evaporation of water is a physical change, as it involves the change of water from a liquid to a gas without any change in its chemical composition.
Burning of Candle Wax
Burning of candle wax is a chemical change, as the heat and oxygen cause the wax to react and form new compounds such as carbon dioxide and water.
Digestion of Food in our Body
Digestion of food in our body involves chemical changes, as the enzymes in our digestive system break down the food into simpler substances that can be used by our body for energy and growth.
Conclusion
Therefore, the correct answer is option B - Evaporation of water, as it is a physical change and does not involve any chemical reactions or the formation of new substances.
Chemical changes involve the formation of new substances with different chemical properties, while physical changes involve changes in the physical state or appearance of a substance without changing its chemical composition.
Cooking of Food
Cooking of food involves chemical changes, as the heat and other ingredients cause chemical reactions that alter the taste, texture, and nutritional value of the food.
Evaporation of Water
Evaporation of water is a physical change, as it involves the change of water from a liquid to a gas without any change in its chemical composition.
Burning of Candle Wax
Burning of candle wax is a chemical change, as the heat and oxygen cause the wax to react and form new compounds such as carbon dioxide and water.
Digestion of Food in our Body
Digestion of food in our body involves chemical changes, as the enzymes in our digestive system break down the food into simpler substances that can be used by our body for energy and growth.
Conclusion
Therefore, the correct answer is option B - Evaporation of water, as it is a physical change and does not involve any chemical reactions or the formation of new substances.
When ferrous sulphate crystals are strongly heated, the gas/vapour not evolved are of- a)SO2
- b)SO3
- c)O2
- d)H2O
Correct answer is option 'C'. Can you explain this answer?
When ferrous sulphate crystals are strongly heated, the gas/vapour not evolved are of
a)
SO2
b)
SO3
c)
O2
d)
H2O
|
Manish iyer answered |
Heating Ferrous Sulphate Crystals
Ferrous sulphate crystals have the chemical formula FeSO4·7H2O. When these crystals are strongly heated, they undergo a decomposition reaction, breaking down into different compounds.
Decomposition Reaction
The decomposition reaction of ferrous sulphate crystals is as follows:
FeSO4·7H2O(s) → Fe2O3(s) + SO3(g) + H2O(g)
According to this reaction, the ferrous sulphate crystals break down into solid iron(III) oxide (Fe2O3), gaseous sulphur trioxide (SO3), and water vapor (H2O).
Evolved Gas/Vapour
The question asks us to identify the gas/vapour that is not evolved during the heating process. From the above reaction, we can see that three different compounds are produced when ferrous sulphate crystals are strongly heated. These are:
- Iron(III) oxide (Fe2O3)
- Sulphur trioxide (SO3)
- Water vapor (H2O)
Out of these three compounds, only one is not a gas/vapour. That compound is iron(III) oxide (Fe2O3).
Therefore, the correct answer to the question is option 'C', which is O2. This is not one of the compounds produced during the heating of ferrous sulphate crystals, and hence it is not the gas/vapour that is not evolved.
Ferrous sulphate crystals have the chemical formula FeSO4·7H2O. When these crystals are strongly heated, they undergo a decomposition reaction, breaking down into different compounds.
Decomposition Reaction
The decomposition reaction of ferrous sulphate crystals is as follows:
FeSO4·7H2O(s) → Fe2O3(s) + SO3(g) + H2O(g)
According to this reaction, the ferrous sulphate crystals break down into solid iron(III) oxide (Fe2O3), gaseous sulphur trioxide (SO3), and water vapor (H2O).
Evolved Gas/Vapour
The question asks us to identify the gas/vapour that is not evolved during the heating process. From the above reaction, we can see that three different compounds are produced when ferrous sulphate crystals are strongly heated. These are:
- Iron(III) oxide (Fe2O3)
- Sulphur trioxide (SO3)
- Water vapor (H2O)
Out of these three compounds, only one is not a gas/vapour. That compound is iron(III) oxide (Fe2O3).
Therefore, the correct answer to the question is option 'C', which is O2. This is not one of the compounds produced during the heating of ferrous sulphate crystals, and hence it is not the gas/vapour that is not evolved.
In which of the following chemical equations, the abbreviations represent the correct states of the reactants and products involved at reaction temperature?
- a)2 H2 (g) + O2 (l) → 2 H2O (l)
- b)2 H2 (l) + O2 (l) → 2 H2O (g)
- c)2 H2 (g) + O2 (g) → 2 H2O (l)
- d)2 H2 (g) + O2 (g) → 2 H2O (g)
Correct answer is option 'C'. Can you explain this answer?
In which of the following chemical equations, the abbreviations represent the correct states of the reactants and products involved at reaction temperature?
a)
2 H2 (g) + O2 (l) → 2 H2O (l)
b)
2 H2 (l) + O2 (l) → 2 H2O (g)
c)
2 H2 (g) + O2 (g) → 2 H2O (l)
d)
2 H2 (g) + O2 (g) → 2 H2O (g)
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|
Ritu Saxena answered |
At the reaction temperature, H2 gas combine with O2 gas to form H2O vapour.
Fe2 O3 + 2 Al → Al2O3 + 2 Fe
The above reaction is an example of a- a)Combination reaction
- b)Double displacement reaction
- c)Displacement reaction
- d)Decomposition reaction
Correct answer is option 'C'. Can you explain this answer?
Fe2 O3 + 2 Al → Al2O3 + 2 Fe
The above reaction is an example of a
The above reaction is an example of a
a)
Combination reaction
b)
Double displacement reaction
c)
Displacement reaction
d)
Decomposition reaction
|
|
Rohit Sharma answered |
It is an example of displacement reaction. Aluminium being more reactive than iron displaces iron and results in the formation of aluminium oxide.
Which of the following statements about the given reaction are correct ?
3 Fe(s) + 4 H2 O(g) → Fe3O4 (s) + 4 H2(g)
(i) Iron metal is getting oxidised
(ii) Water is getting reduced
(iii) Water is acting as reducing agent
(iv) Water is acting as oxidising agent.- a)(i), (ii) and (iii)
- b)(iii) and (iv)
- c)(i), (ii) and (iv)
- d)(ii) and (iv)
Correct answer is option 'C'. Can you explain this answer?
Which of the following statements about the given reaction are correct ?
3 Fe(s) + 4 H2 O(g) → Fe3O4 (s) + 4 H2(g)
(i) Iron metal is getting oxidised
(ii) Water is getting reduced
(iii) Water is acting as reducing agent
(iv) Water is acting as oxidising agent.
3 Fe(s) + 4 H2 O(g) → Fe3O4 (s) + 4 H2(g)
(i) Iron metal is getting oxidised
(ii) Water is getting reduced
(iii) Water is acting as reducing agent
(iv) Water is acting as oxidising agent.
a)
(i), (ii) and (iii)
b)
(iii) and (iv)
c)
(i), (ii) and (iv)
d)
(ii) and (iv)
|
Vivek Bansal answered |
Here, oxygen combines with water to get oxidized. Oxygen is removed from water hence, it is getting reduced. Water is providing oxygen and it acts as an oxidizing agent.
- On introducing two molecules to each other, one molecule loses an electron. This reaction is called oxidation.
- On introducing two molecules to each other, one molecule gains an electron. This reaction is called reduction.
- The oxidized substance is called a reduction agent. The reduced substance is called an oxidizing agent.
Which of the following is (are) on endothermic process(es)?
(i) Dilution of sulphuric acid
(ii) Sublimation of dry ice
(iii) Condensation of water vapours
(iv) Evaporation of water- a)(i) and (ii)
- b)(ii) and (iv)
- c)(ii) only
- d)(iii) only
Correct answer is option 'B'. Can you explain this answer?
Which of the following is (are) on endothermic process(es)?
(i) Dilution of sulphuric acid
(ii) Sublimation of dry ice
(iii) Condensation of water vapours
(iv) Evaporation of water
(i) Dilution of sulphuric acid
(ii) Sublimation of dry ice
(iii) Condensation of water vapours
(iv) Evaporation of water
a)
(i) and (ii)
b)
(ii) and (iv)
c)
(ii) only
d)
(iii) only
|
Khusboo jain answered |
Endothermic Processes
Dilution of sulphuric acid
- Dilution of sulphuric acid is an exothermic process as it releases heat during the reaction.
Sublimation of dry ice
- Sublimation of dry ice is an endothermic process as it requires heat input to change the solid directly into a gas without passing through the liquid phase.
Condensation of water vapours
- Condensation of water vapours is an exothermic process as it releases heat when water vapours change into liquid water.
Evaporation of water
- Evaporation of water is an endothermic process as it requires heat input to change liquid water into water vapour.
Therefore, the endothermic processes in the given options are (ii) Sublimation of dry ice and (iv) Evaporation of water. So, the correct answer is option B - (ii) and (iv).
Dilution of sulphuric acid
- Dilution of sulphuric acid is an exothermic process as it releases heat during the reaction.
Sublimation of dry ice
- Sublimation of dry ice is an endothermic process as it requires heat input to change the solid directly into a gas without passing through the liquid phase.
Condensation of water vapours
- Condensation of water vapours is an exothermic process as it releases heat when water vapours change into liquid water.
Evaporation of water
- Evaporation of water is an endothermic process as it requires heat input to change liquid water into water vapour.
Therefore, the endothermic processes in the given options are (ii) Sublimation of dry ice and (iv) Evaporation of water. So, the correct answer is option B - (ii) and (iv).
Which one of the following does not result in the evolution of H2 gas?- a)Zinc and hydrochloric acid
- b)Iron and sulphuric acid
- c)Magnesium and very dilute nitric acid
- d)Aluminium and nitric acid
Correct answer is option 'D'. Can you explain this answer?
Which one of the following does not result in the evolution of H2 gas?
a)
Zinc and hydrochloric acid
b)
Iron and sulphuric acid
c)
Magnesium and very dilute nitric acid
d)
Aluminium and nitric acid
|
|
Rohini chauhan answered |
Explanation:
The reaction between a metal and an acid usually results in the evolution of hydrogen gas. However, there are certain conditions under which this reaction may not occur. In this case, we are given four different reactions and we have to identify which one does not result in the evolution of H2 gas.
Zinc and hydrochloric acid:
When zinc reacts with hydrochloric acid, it undergoes a displacement reaction and produces zinc chloride and hydrogen gas. The balanced chemical equation for this reaction is:
Zn + 2HCl → ZnCl2 + H2
Iron and sulphuric acid:
When iron reacts with sulfuric acid, it also undergoes a displacement reaction and produces iron(II) sulfate and hydrogen gas. The balanced chemical equation for this reaction is:
Fe + H2SO4 → FeSO4 + H2
Magnesium and very dilute nitric acid:
When magnesium reacts with nitric acid, it undergoes a redox reaction and produces magnesium nitrate, nitrogen dioxide gas, and water. The balanced chemical equation for this reaction is:
3Mg + 8HNO3 → 3Mg(NO3)2 + 2NO + 4H2O
Aluminium and nitric acid:
When aluminium reacts with nitric acid, it also undergoes a redox reaction and produces aluminium nitrate, nitrogen dioxide gas, and water. The balanced chemical equation for this reaction is:
2Al + 6HNO3 → 2Al(NO3)3 + 3H2O + 3NO2
From the above equations, we can see that all the reactions except the one involving aluminium and nitric acid result in the evolution of hydrogen gas. Therefore, the correct answer is option 'D' - Aluminium and nitric acid.
The reaction between a metal and an acid usually results in the evolution of hydrogen gas. However, there are certain conditions under which this reaction may not occur. In this case, we are given four different reactions and we have to identify which one does not result in the evolution of H2 gas.
Zinc and hydrochloric acid:
When zinc reacts with hydrochloric acid, it undergoes a displacement reaction and produces zinc chloride and hydrogen gas. The balanced chemical equation for this reaction is:
Zn + 2HCl → ZnCl2 + H2
Iron and sulphuric acid:
When iron reacts with sulfuric acid, it also undergoes a displacement reaction and produces iron(II) sulfate and hydrogen gas. The balanced chemical equation for this reaction is:
Fe + H2SO4 → FeSO4 + H2
Magnesium and very dilute nitric acid:
When magnesium reacts with nitric acid, it undergoes a redox reaction and produces magnesium nitrate, nitrogen dioxide gas, and water. The balanced chemical equation for this reaction is:
3Mg + 8HNO3 → 3Mg(NO3)2 + 2NO + 4H2O
Aluminium and nitric acid:
When aluminium reacts with nitric acid, it also undergoes a redox reaction and produces aluminium nitrate, nitrogen dioxide gas, and water. The balanced chemical equation for this reaction is:
2Al + 6HNO3 → 2Al(NO3)3 + 3H2O + 3NO2
From the above equations, we can see that all the reactions except the one involving aluminium and nitric acid result in the evolution of hydrogen gas. Therefore, the correct answer is option 'D' - Aluminium and nitric acid.
Which of the following substance is reduced in the given reaction below?
PbS(s) + 4H2O2 (aq) → PbSO4(s) + 4H2O- a)Lead sulphide
- b)Hydrogen peroxide
- c)Both lead sulphide and Hydrogen peroxide
- d)Water
Correct answer is option 'B'. Can you explain this answer?
Which of the following substance is reduced in the given reaction below?
PbS(s) + 4H2O2 (aq) → PbSO4(s) + 4H2O
PbS(s) + 4H2O2 (aq) → PbSO4(s) + 4H2O
a)
Lead sulphide
b)
Hydrogen peroxide
c)
Both lead sulphide and Hydrogen peroxide
d)
Water
|
Rahul agarwal answered |
Understanding the Reaction
In the reaction:
PbS(s) + 4H2O2(aq) → PbSO4(s) + 4H2O,
we need to identify which substance is reduced.
Reduction Process
- Definition of Reduction: Reduction is a chemical reaction that involves the gain of electrons or a decrease in oxidation state by a molecule, atom, or ion.
Analyzing Hydrogen Peroxide
- Hydrogen Peroxide (H2O2): In this reaction, H2O2 acts as an oxidizing agent. It is known to undergo reduction during the reaction.
- Oxidation State Change: The oxidation state of oxygen in H2O2 is -1, and in water (H2O), it is -2. This change indicates that H2O2 is gaining electrons and being reduced.
Analyzing Lead Sulfide
- Lead Sulfide (PbS): In this reaction, PbS is converted to PbSO4.
- Oxidation State Change: Lead (Pb) in PbS has an oxidation state of +2 in PbSO4, but the lead does not gain electrons. Instead, it is oxidized.
Conclusion
- Final Identification: Since H2O2 is reduced (gaining electrons) and PbS is oxidized (losing electrons), the correct answer is indeed b) Hydrogen peroxide.
Thus, understanding the changes in oxidation states helps clarify the reduction process in this reaction.
In the reaction:
PbS(s) + 4H2O2(aq) → PbSO4(s) + 4H2O,
we need to identify which substance is reduced.
Reduction Process
- Definition of Reduction: Reduction is a chemical reaction that involves the gain of electrons or a decrease in oxidation state by a molecule, atom, or ion.
Analyzing Hydrogen Peroxide
- Hydrogen Peroxide (H2O2): In this reaction, H2O2 acts as an oxidizing agent. It is known to undergo reduction during the reaction.
- Oxidation State Change: The oxidation state of oxygen in H2O2 is -1, and in water (H2O), it is -2. This change indicates that H2O2 is gaining electrons and being reduced.
Analyzing Lead Sulfide
- Lead Sulfide (PbS): In this reaction, PbS is converted to PbSO4.
- Oxidation State Change: Lead (Pb) in PbS has an oxidation state of +2 in PbSO4, but the lead does not gain electrons. Instead, it is oxidized.
Conclusion
- Final Identification: Since H2O2 is reduced (gaining electrons) and PbS is oxidized (losing electrons), the correct answer is indeed b) Hydrogen peroxide.
Thus, understanding the changes in oxidation states helps clarify the reduction process in this reaction.
Which among the following is called double displacement reaction (s)?
(i) Pb + CuCl2 → PbCl2 + Cu
(ii) Na2 SO4 + BaCl2 → BaSO4 + 2 NaCl
(iii) C + O2 → CO2
(iv) CH4 + 2 O2 → CO2 + 2H2O- a)(i) and (iv)
- b)(ii) and (i)
- c)(ii) only
- d)(iii) and (iv)
Correct answer is option 'C'. Can you explain this answer?
Which among the following is called double displacement reaction (s)?
(i) Pb + CuCl2 → PbCl2 + Cu
(ii) Na2 SO4 + BaCl2 → BaSO4 + 2 NaCl
(iii) C + O2 → CO2
(iv) CH4 + 2 O2 → CO2 + 2H2O
(i) Pb + CuCl2 → PbCl2 + Cu
(ii) Na2 SO4 + BaCl2 → BaSO4 + 2 NaCl
(iii) C + O2 → CO2
(iv) CH4 + 2 O2 → CO2 + 2H2O
a)
(i) and (iv)
b)
(ii) and (i)
c)
(ii) only
d)
(iii) and (iv)
|
|
Radha Iyer answered |
The reactions in which two compounds react by an exchange of ions to form two new compounds are called double displacement reactions. In double replacement reactions, the positive ions exchange negative ion partners. A double replacement reaction is represented by the general equation.
AB + CD → AD + CB
In a double displacement reaction, atoms from two different compounds switch places. The reactants are two compounds and the products are two different compounds.
Na2SO4 + BaCl2 → BaSO4 + 2NaCl
AB + CD → AD + CB
In a double displacement reaction, atoms from two different compounds switch places. The reactants are two compounds and the products are two different compounds.
Na2SO4 + BaCl2 → BaSO4 + 2NaCl
Which of the following metal will react with dilute hydrochloric acid to give out hydrogen gas- a)Cu
- b)Pb
- c)Ag
- d)Hg
Correct answer is option 'B'. Can you explain this answer?
Which of the following metal will react with dilute hydrochloric acid to give out hydrogen gas
a)
Cu
b)
Pb
c)
Ag
d)
Hg
|
Niyati kapoor answered |
**Answer:**
**Introduction:**
When a metal reacts with an acid, it displaces hydrogen from the acid, resulting in the formation of a salt and the evolution of hydrogen gas. This type of reaction is known as a displacement reaction.
**Explanation:**
Among the given options, the metal that will react with dilute hydrochloric acid to give out hydrogen gas is Pb (lead). The reaction between lead and hydrochloric acid can be represented by the following equation:
Pb + 2HCl → PbCl2 + H2
**Reasoning:**
To determine which metal will react with hydrochloric acid, we need to consider the reactivity series of metals. The reactivity series is a list of metals in order of their reactivity, with the most reactive metal at the top and the least reactive metal at the bottom.
The reactivity series of metals is as follows:
Potassium (K) > Sodium (Na) > Calcium (Ca) > Magnesium (Mg) > Aluminum (Al) > Zinc (Zn) > Iron (Fe) > Lead (Pb) > Hydrogen (H) > Copper (Cu) > Silver (Ag) > Gold (Au)
According to the reactivity series, metals higher in the series are more reactive than metals lower in the series. This means that metals higher in the series can displace metals lower in the series from their compounds.
In the given options, lead (Pb) is below hydrogen (H) in the reactivity series. This means that lead can displace hydrogen from hydrochloric acid to form lead chloride (PbCl2) and release hydrogen gas (H2).
Therefore, the correct answer is option B - Pb.
**Introduction:**
When a metal reacts with an acid, it displaces hydrogen from the acid, resulting in the formation of a salt and the evolution of hydrogen gas. This type of reaction is known as a displacement reaction.
**Explanation:**
Among the given options, the metal that will react with dilute hydrochloric acid to give out hydrogen gas is Pb (lead). The reaction between lead and hydrochloric acid can be represented by the following equation:
Pb + 2HCl → PbCl2 + H2
**Reasoning:**
To determine which metal will react with hydrochloric acid, we need to consider the reactivity series of metals. The reactivity series is a list of metals in order of their reactivity, with the most reactive metal at the top and the least reactive metal at the bottom.
The reactivity series of metals is as follows:
Potassium (K) > Sodium (Na) > Calcium (Ca) > Magnesium (Mg) > Aluminum (Al) > Zinc (Zn) > Iron (Fe) > Lead (Pb) > Hydrogen (H) > Copper (Cu) > Silver (Ag) > Gold (Au)
According to the reactivity series, metals higher in the series are more reactive than metals lower in the series. This means that metals higher in the series can displace metals lower in the series from their compounds.
In the given options, lead (Pb) is below hydrogen (H) in the reactivity series. This means that lead can displace hydrogen from hydrochloric acid to form lead chloride (PbCl2) and release hydrogen gas (H2).
Therefore, the correct answer is option B - Pb.
Which one of the following solution on mixing will not form a precipitate?- a)Lead acetate and potassium iodide
- b)Lead nitrate and sulphuric acid
- c)Iron sulphide and dilute sulphuric acid
- d)Potassium bromide and silver nitrate
Correct answer is option 'C'. Can you explain this answer?
Which one of the following solution on mixing will not form a precipitate?
a)
Lead acetate and potassium iodide
b)
Lead nitrate and sulphuric acid
c)
Iron sulphide and dilute sulphuric acid
d)
Potassium bromide and silver nitrate
|
Tanishq Iyer answered |
Explanation:
Iron sulphide and dilute sulphuric acid:
- When iron sulphide reacts with dilute sulphuric acid, it forms hydrogen sulfide gas and iron(II) sulfate.
- Since hydrogen sulfide gas is a gas and not a solid, no precipitate is formed in this reaction.
- Therefore, this combination will not form a precipitate.
Lead acetate and potassium iodide:
- When lead acetate reacts with potassium iodide, it forms lead iodide which is insoluble in water and hence, a yellow precipitate of lead iodide is formed.
Lead nitrate and sulphuric acid:
- When lead nitrate reacts with sulphuric acid, it forms lead sulfate which is insoluble in water and hence, a white precipitate of lead sulfate is formed.
Potassium bromide and silver nitrate:
- When potassium bromide reacts with silver nitrate, it forms silver bromide which is insoluble in water and hence, a cream precipitate of silver bromide is formed.
Therefore, out of the given options, only the combination of iron sulphide and dilute sulphuric acid will not form a precipitate.
Iron sulphide and dilute sulphuric acid:
- When iron sulphide reacts with dilute sulphuric acid, it forms hydrogen sulfide gas and iron(II) sulfate.
- Since hydrogen sulfide gas is a gas and not a solid, no precipitate is formed in this reaction.
- Therefore, this combination will not form a precipitate.
Lead acetate and potassium iodide:
- When lead acetate reacts with potassium iodide, it forms lead iodide which is insoluble in water and hence, a yellow precipitate of lead iodide is formed.
Lead nitrate and sulphuric acid:
- When lead nitrate reacts with sulphuric acid, it forms lead sulfate which is insoluble in water and hence, a white precipitate of lead sulfate is formed.
Potassium bromide and silver nitrate:
- When potassium bromide reacts with silver nitrate, it forms silver bromide which is insoluble in water and hence, a cream precipitate of silver bromide is formed.
Therefore, out of the given options, only the combination of iron sulphide and dilute sulphuric acid will not form a precipitate.
What is the corresponding change in colour when iron nail is dipped in the blue copper sulphate solution?- a)Red
- b)White
- c)Green
- d)Black
Correct answer is option 'C'. Can you explain this answer?
What is the corresponding change in colour when iron nail is dipped in the blue copper sulphate solution?
a)
Red
b)
White
c)
Green
d)
Black
|
Deepali patil answered |
Explanation:
When an iron nail is dipped in a blue copper sulphate solution, a chemical reaction occurs between iron and copper sulphate. This reaction results in the displacement of copper ions by iron ions.
Colour Change:
The blue colour of the copper sulphate solution changes to a greenish color when the iron nail is dipped into it.
Reason for Colour Change:
The blue color of the copper sulphate solution is due to the presence of copper ions (Cu2+) in the solution. When the iron nail is dipped into the solution, iron ions (Fe2+) are formed by the displacement of copper ions. The greenish color is due to the formation of iron sulphate (FeSO4) in the solution.
Chemical Reaction:
The chemical reaction between iron and copper sulphate can be represented as follows:
Fe(s) + CuSO4(aq) → FeSO4(aq) + Cu(s)
In this reaction, iron (Fe) displaces copper (Cu) from copper sulphate (CuSO4) to form iron sulphate (FeSO4) and copper metal (Cu).
Conclusion:
When an iron nail is dipped in a blue copper sulphate solution, the blue color of the solution changes to a greenish color due to the formation of iron sulphate. This change in color is an indication of the chemical reaction between iron and copper sulphate.
When an iron nail is dipped in a blue copper sulphate solution, a chemical reaction occurs between iron and copper sulphate. This reaction results in the displacement of copper ions by iron ions.
Colour Change:
The blue colour of the copper sulphate solution changes to a greenish color when the iron nail is dipped into it.
Reason for Colour Change:
The blue color of the copper sulphate solution is due to the presence of copper ions (Cu2+) in the solution. When the iron nail is dipped into the solution, iron ions (Fe2+) are formed by the displacement of copper ions. The greenish color is due to the formation of iron sulphate (FeSO4) in the solution.
Chemical Reaction:
The chemical reaction between iron and copper sulphate can be represented as follows:
Fe(s) + CuSO4(aq) → FeSO4(aq) + Cu(s)
In this reaction, iron (Fe) displaces copper (Cu) from copper sulphate (CuSO4) to form iron sulphate (FeSO4) and copper metal (Cu).
Conclusion:
When an iron nail is dipped in a blue copper sulphate solution, the blue color of the solution changes to a greenish color due to the formation of iron sulphate. This change in color is an indication of the chemical reaction between iron and copper sulphate.
Green coating on copper in rainy season is due to the formation of- a)CuCO3
- b)Cu(OH)2
- c)CuCO3.Cu(OH)2
- d)CuS
Correct answer is option 'C'. Can you explain this answer?
Green coating on copper in rainy season is due to the formation of
a)
CuCO3
b)
Cu(OH)2
c)
CuCO3.Cu(OH)2
d)
CuS
|
|
Ritu Saxena answered |
Copper metal when exposed to air turns green in colour due to corrosion. Thus, when copper vessels are exposed to air in rainy season for sometime, the metal reacts with gases and moisture present in air to form a mixture of copper carbonate and copper hydroxide [(CuCO3).Cu(OH)2]. This gives a green colour to the vessels
Which one of the following on mixing with water will result in rise of temperature?- a)Sodium chloride
- b)Sodium hydroxide
- c)Potassium nitrate
- d)CuSO4.5H2O
Correct answer is option 'A'. Can you explain this answer?
Which one of the following on mixing with water will result in rise of temperature?
a)
Sodium chloride
b)
Sodium hydroxide
c)
Potassium nitrate
d)
CuSO4.5H2O
|
Isha Dasgupta answered |
Rise of temperature on mixing with water: Sodium chloride
When certain substances are mixed with water, they can either absorb heat energy from the surroundings (endothermic reaction) or release heat energy into the surroundings (exothermic reaction). In this case, we are looking for the substance that will result in a rise of temperature when mixed with water.
Explanation:
- Sodium chloride (NaCl): When sodium chloride is mixed with water, it undergoes a highly exothermic reaction. This means that it releases heat energy into the surroundings, causing a rise in temperature. The dissolution of sodium chloride in water is an exothermic process because it involves the formation of new bonds between the sodium and chloride ions and the water molecules. The heat released during this process raises the temperature of the solution.
- Sodium hydroxide (NaOH): When sodium hydroxide is mixed with water, it also undergoes an exothermic reaction. However, the heat released is not as significant as in the case of sodium chloride. The dissolution of sodium hydroxide in water is also exothermic, but the reaction is less vigorous compared to sodium chloride.
- Potassium nitrate (KNO3): When potassium nitrate is mixed with water, it undergoes an endothermic reaction. This means that it absorbs heat energy from the surroundings, causing a decrease in temperature. The dissolution of potassium nitrate in water requires energy to break the bonds between the potassium and nitrate ions, resulting in a cooling effect.
- CuSO4·5H2O: Copper sulfate pentahydrate (CuSO4·5H2O) is a hydrated compound, which means it contains water molecules within its crystal structure. When it is mixed with water, the water molecules already present in the crystal structure are released, but this process does not result in a significant rise in temperature.
Based on the above explanations, the correct answer is option 'A' - Sodium chloride.
When certain substances are mixed with water, they can either absorb heat energy from the surroundings (endothermic reaction) or release heat energy into the surroundings (exothermic reaction). In this case, we are looking for the substance that will result in a rise of temperature when mixed with water.
Explanation:
- Sodium chloride (NaCl): When sodium chloride is mixed with water, it undergoes a highly exothermic reaction. This means that it releases heat energy into the surroundings, causing a rise in temperature. The dissolution of sodium chloride in water is an exothermic process because it involves the formation of new bonds between the sodium and chloride ions and the water molecules. The heat released during this process raises the temperature of the solution.
- Sodium hydroxide (NaOH): When sodium hydroxide is mixed with water, it also undergoes an exothermic reaction. However, the heat released is not as significant as in the case of sodium chloride. The dissolution of sodium hydroxide in water is also exothermic, but the reaction is less vigorous compared to sodium chloride.
- Potassium nitrate (KNO3): When potassium nitrate is mixed with water, it undergoes an endothermic reaction. This means that it absorbs heat energy from the surroundings, causing a decrease in temperature. The dissolution of potassium nitrate in water requires energy to break the bonds between the potassium and nitrate ions, resulting in a cooling effect.
- CuSO4·5H2O: Copper sulfate pentahydrate (CuSO4·5H2O) is a hydrated compound, which means it contains water molecules within its crystal structure. When it is mixed with water, the water molecules already present in the crystal structure are released, but this process does not result in a significant rise in temperature.
Based on the above explanations, the correct answer is option 'A' - Sodium chloride.
The process of coating iron with zinc is called- a)Electroplating
- b)Reduction
- c)Polishing
- d)Galvanisation
Correct answer is option 'D'. Can you explain this answer?
The process of coating iron with zinc is called
a)
Electroplating
b)
Reduction
c)
Polishing
d)
Galvanisation
|
|
Ritu Saxena answered |
Galvanisation is the process of coating iron with zinc in order to prevent its rusting.
Rancidity is due to- a)Combination of oils and fats
- b)Displacement of oils and fats
- c)Oxidation of oils and fats
- d)Reduction of oils and fats
Correct answer is option 'C'. Can you explain this answer?
Rancidity is due to
a)
Combination of oils and fats
b)
Displacement of oils and fats
c)
Oxidation of oils and fats
d)
Reduction of oils and fats
|
|
Radha Iyer answered |
Rancidity is a very general term and in its most general meaning, it refers to the spoilage of food in such a way that it becomes undesirable for consumption. Food turns rancid when the fats and oils within them get oxidized and the taste and smell of the food change due to this reason.
Rust is- a)Fe2O3
- b)FeSO4
- c)Fe2O3.xH2O
- d)Fe2O3 H2O
Correct answer is option 'C'. Can you explain this answer?
Rust is
a)
Fe2O3
b)
FeSO4
c)
Fe2O3.xH2O
d)
Fe2O3 H2O
|
|
Priyanka Kapoor answered |
Rust is iron oxide. iron is a metal. generally, metallic oxides are basic in nature.
Rust is basic in nature. we know about this because when rust reacts with O2 and H2O it releases metallic oxides which are basic in nature.
when we take some amount of rust and put it in a small amount of water and after shaking the liquid when we test the solution with a rd litmus paper, it turns blue. this shows that rust is a basic oxide
Rust is basic in nature. we know about this because when rust reacts with O2 and H2O it releases metallic oxides which are basic in nature.
when we take some amount of rust and put it in a small amount of water and after shaking the liquid when we test the solution with a rd litmus paper, it turns blue. this shows that rust is a basic oxide
Which of the following are exothermic processes?
(i) Reaction of water with quick lime
(ii) Dilution of an acid
(iii) Evaporation of water
(iv) Sublimation of camphor (crystals)- a)(i) and (ii)
- b)(ii) and (iii)
- c)(i) and (iv)
- d)(iii) and (iv)
Correct answer is option 'A'. Can you explain this answer?
Which of the following are exothermic processes?
(i) Reaction of water with quick lime
(ii) Dilution of an acid
(iii) Evaporation of water
(iv) Sublimation of camphor (crystals)
(i) Reaction of water with quick lime
(ii) Dilution of an acid
(iii) Evaporation of water
(iv) Sublimation of camphor (crystals)
a)
(i) and (ii)
b)
(ii) and (iii)
c)
(i) and (iv)
d)
(iii) and (iv)
|
|
Priyanka Kapoor answered |
Exothermic reactions are chemical reactions that release energy as heat or light.
- A large amount of heat is released when quick lime reacts with water, along with the formation of calcium hydroxide.
- Similarly, the process of dissolving an acid or base in water is a highly exothermic reaction. Water should never be added to acid, but the acid can be added to water for dilution.
- Evaporation of water and sublimation of camphor are endothermic reactions.
Respiration is- a)An exothermic process
- b)An endothermic process
- c)Neither exothermic nor endothermic
- d)Can be exothermic or endothermic
Correct answer is option 'A'. Can you explain this answer?
Respiration is
a)
An exothermic process
b)
An endothermic process
c)
Neither exothermic nor endothermic
d)
Can be exothermic or endothermic
|
|
Priyanka Kapoor answered |
Respiration is the process in which the cells of an organism obtain energy by combining oxygen and glucose, resulting in the release of carbon dioxide, water, and ATP (energy).
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