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Science Olympiad Test: Chemical Reactions and Equations- 2 - Class 10 MCQ


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15 Questions MCQ Test - Science Olympiad Test: Chemical Reactions and Equations- 2

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Science Olympiad Test: Chemical Reactions and Equations- 2 - Question 1

Rust is

Detailed Solution for Science Olympiad Test: Chemical Reactions and Equations- 2 - Question 1

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

Science Olympiad Test: Chemical Reactions and Equations- 2 - Question 2

Fe2 O3 + 2 Al → Al2O3 + 2 Fe
The above reaction is an example of a

Detailed Solution for Science Olympiad Test: Chemical Reactions and Equations- 2 - Question 2

It is an example of displacement reaction. Aluminium being more reactive than iron displaces iron and results in the formation of aluminium oxide.

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Science Olympiad Test: Chemical Reactions and Equations- 2 - Question 3

In which of the following chemical equations, the abbreviations represent the correct states of the reactants and products involved at reaction temperature?

Detailed Solution for Science Olympiad Test: Chemical Reactions and Equations- 2 - Question 3

Option 3 is the correct answer.
During the formation of Water, both Hydrogen and Oxygen are in gaseous form and produce Water in liquid form.
The reaction proceeds as follows:
2 H2 (g) + O2 (g) → 2 H2O (l)
The preceding process shows the synthesis of Water from Hydrogen and Oxygen gas.
Two moles of Hydrogen in the gaseous state react with one mole of Oxygen in the gaseous state to form two moles of Water in the liquid state in this reaction.

Science Olympiad Test: Chemical Reactions and Equations- 2 - Question 4

Which one of the following solution on mixing will not form a precipitate?

Detailed Solution for Science Olympiad Test: Chemical Reactions and Equations- 2 - Question 4

It forms solution of ferrous sulphate and hydrogen sulphide gas. 
FeS + H2SO4 → FeSO​4 + H2S.

Science Olympiad Test: Chemical Reactions and Equations- 2 - Question 5

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

Detailed Solution for Science Olympiad Test: Chemical Reactions and Equations- 2 - Question 5

Sublimation of dry ice and evaporation of water both are endothermic process and these heat (energy) from their surrounding to get sublime or evaporate. Hence, both these processes produce cooling. This is the reason for using dry ice as refrigerant.
Dilution of sulphuric acid and condensation of water vapours evolve heat. Hence, these are exothermic processes.

Science Olympiad Test: Chemical Reactions and Equations- 2 - Question 6

When a black and white photographic film is exposed to light, the grey colour on the photographic film is due to presence of

Detailed Solution for Science Olympiad Test: Chemical Reactions and Equations- 2 - Question 6

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.

Science Olympiad Test: Chemical Reactions and Equations- 2 - Question 7

Electrolysis of water is decomposition reaction. The mole ratio of hydrogen and oxygen gases liberated during electrolysis of water is

Detailed Solution for Science Olympiad Test: Chemical Reactions and Equations- 2 - Question 7


Mole ratio of H2 to O2 liberated = 2 : 1.

Science Olympiad Test: Chemical Reactions and Equations- 2 - Question 8

Green coating on copper in rainy season is due to the formation of

Detailed Solution for Science Olympiad Test: Chemical Reactions and Equations- 2 - Question 8

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

Science Olympiad Test: Chemical Reactions and Equations- 2 - Question 9

Which of the following substance is reduced in the given reaction below?
PbS(s) + 4H2O2 (aq) → PbSO4(s) + 4H2O

Detailed Solution for Science Olympiad Test: Chemical Reactions and Equations- 2 - Question 9

Oxidised: PbS: The oxidation number of S increases from -2 to +6. Thus, S itself is oxidised and acts as reducing agent.
Reduced: H2​O2​: The oxidation number of O decreases from -1 to -2. Thus, O itself is reduced and acts as oxidising agent.

Science Olympiad Test: Chemical Reactions and Equations- 2 - Question 10

A balanced chemical equation is in accordance with which one of the following laws given below

Detailed Solution for Science Olympiad Test: Chemical Reactions and Equations- 2 - Question 10
  • The Law of conservation of mass states that mass can neither be created nor destroyed but can be transformed from one form to another.
  • A balanced chemical equation is in accordance with the law of conservation of mass i.e the atoms of the reactants are just rearranged to form products but the total amount of mass in chemical reaction remains constant.
  • Avogadro's Law states that at the constant temperature and pressure, the volumes of gas is directly proportional to the number of molecules.
  • Law of multiple proportion states that when two elements combine to form two or more compounds, then the ratio of the mass of one element that combines with the fixed mass of the other element will always be simple whole numbers.
  • Gay-Lussac's Law of gaseous volumes states that at constant volume, the pressure of the given mass of a gas is directly proportional to the temperature in Kelvin.
Science Olympiad Test: Chemical Reactions and Equations- 2 - Question 11

Which one of the following does not result in the evolution of H2 gas?

Detailed Solution for Science Olympiad Test: Chemical Reactions and Equations- 2 - Question 11
  • Hydrogen gas is not evolved when there is a reaction between metal and Nitric acid (HNO3)occurs as Nitric acid is a strong oxidizing agent.
  • The Hydrogen gas produced during the reaction with metal gets oxidized to H2O, hence no hydrogen gas is produced.
  • Instead, it evolves nitric oxides such as NO2​,NO etc.
  • Example: When a Silver metal reacts with Nitric acid (HNO3)to give N2O and H2O.
Science Olympiad Test: Chemical Reactions and Equations- 2 - Question 12

Which one of the following on mixing with water will result in rise of temperature?

Detailed Solution for Science Olympiad Test: Chemical Reactions and Equations- 2 - Question 12

The mixing or dissolution of Sodium chloride in water is an endothermic reaction, i.e. when it takes place it increases the temperature of the solution by absorption of heat resulting in increase in temperature of the reaction mixture which increases the solubility of sodium chloride.

Science Olympiad Test: Chemical Reactions and Equations- 2 - Question 13

Which one of the following is not a chemical change?

Detailed Solution for Science Olympiad Test: Chemical Reactions and Equations- 2 - Question 13

The evaporation of water is a physical change. When water evaporates, it changes from the liquid state to the gas state, but it is still water; it has not changed into any other substance. All changes of state are physical changes.

Science Olympiad Test: Chemical Reactions and Equations- 2 - Question 14

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

Detailed Solution for Science Olympiad Test: Chemical Reactions and Equations- 2 - Question 14

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

Science Olympiad Test: Chemical Reactions and Equations- 2 - Question 15

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)

Detailed Solution for Science Olympiad Test: Chemical Reactions and Equations- 2 - Question 15

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.
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