Q1:
Question for Assertion & Reason Type Questions: Acids, Bases and Salts
Try yourself: Directions: In the following questions, a statement of assertion (A) is followed by a statement of reason (R). Mark the correct choice as:Assertion: After white washing the walls, a shiny white finish on walls is obtained after two to three days.
Reason: Calcium Oxide reacts with Carbon dioxide to form Calcium Hydrogen Carbonate which gives shiny white finish.
Explanation
Calcium hydroxide is obtained by reaction of calcium oxide and water.
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Q2:
Question for Assertion & Reason Type Questions: Acids, Bases and Salts
Try yourself:Assertion (A): When zinc is added to dilute hydrochloric acid, hydrogen is given off.
Reason (R): Hydrochloric acid molecules contain chloride and hydroxide ions.
Explanation
Assertion (A) is true. When zinc is added to dilute hydrochloric acid, a chemical reaction takes place in which hydrogen gas is given off. This is because zinc is more reactive than hydrogen and is able to displace hydrogen atoms from the hydrochloric acid molecules. The chemical equation for this reaction is:
Zn + 2HCl → ZnCl2 + H2
Reason (R) is false. Hydrochloric acid does not contain hydroxide ions. It is a strong acid that contains hydrogen ions (H+) and chloride ions (Cl-). The chemical formula for hydrochloric acid is HCl.
Therefore, the correct answer is (2) Assertion (A) is true but reason (R) is false.
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Q3:
Question for Assertion & Reason Type Questions: Acids, Bases and Salts
Try yourself: Assertion (A): Gas bubbles are observed when sodium carbonate is added to dilute hydrochloric acid.Reason (R): Carbon dioxide is given off in the reaction.
Explanation
Sodium carbonate reacts with excess hydrochloric acid to form sodium chloride, water and carbon dioxide. In this reaction, bubbles of carbon dioxide are observed.
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Q4:
Question for Assertion & Reason Type Questions: Acids, Bases and Salts
Try yourself: Assertion (A): Ammonia solution is an alkali.Reason (R): Ammonia solution turns blue litmus paper red.
Explanation
Ammonia solution, which is alkaline, turns the red litmus paper blue.
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Q5:
Question for Assertion & Reason Type Questions: Acids, Bases and Salts
Try yourself:Directions: In the following questions, a statement of assertion (A) is followed by a statement of reason (R). Mark the correct choice as:
Assertion (A): When common salt is kept open, it absorbs moisture from the air.
Reason (R): Common salt contains magnesium chloride.
Explanation
Assertion (A) is true. When common salt, also known as sodium chloride, is exposed to humid air, it absorbs moisture from the air. This is because the salt molecules are hygroscopic, meaning they have a tendency to absorb water from the air.
Reason (R) is false. Common salt does not contain magnesium chloride. It is a compound of sodium and chlorine, with the chemical formula NaCl.
Therefore, the correct answer is (1) Assertion (A) is true but reason (R) is false.
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Q6:
Question for Assertion & Reason Type Questions: Acids, Bases and Salts
Try yourself: Assertion (A): Baking soda creates acidity in the stomach.Reason (R): Baking soda is alkaline.
Explanation
Baking soda, being alkaline, neutralises the acidity in the stomach and removes it.
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Q7:
Question for Assertion & Reason Type Questions: Acids, Bases and Salts
Try yourself: Assertion (A): Plaster of Paris is used by doctors for setting fractured bones.Reason (R): When Plaster of Paris is mixed with water and applied around the fractured limbs, it sets into a hard mass.
Explanation
Plaster of Paris when mixed with water and applied around the fractured limbs, it sets into a hard mass and keeps the bone joints in a fixed position. So, it is commonly used for setting fractured bones.
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Q8:
Question for Assertion & Reason Type Questions: Acids, Bases and Salts
Try yourself:Direction: In the Following Questions, A Statement of Assertion (A) Is Followed by A Statement of Reason (R). Mark The Correct Choice As:
Assertion: While dissolving an acid or base in water, the acids must always be added slowly to water with constant stirring.
Reason: Dissolving an acid on a base in water is a highly exothermic reaction.
Explanation
Both assertion (A) and reason (R) are true and reason (R) is the correct explanation of assertion (A).
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Q9:
Question for Assertion & Reason Type Questions: Acids, Bases and Salts
Try yourself:Assertion : On adding H2SO4 to water the resulting aqueous solution gets corrosive.
Reason: Hydronium ions are responsible for corrosive action.
Explanation
Because H2SO4 is a strong acid, it readily forms hydronium ions when dissolved in water which are responsible for its corrosive action.
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Q10:
Question for Assertion & Reason Type Questions: Acids, Bases and Salts
Try yourself:Assertion : Phenolphthalein gives pink colour in basic solution.
Reason : Phenolphthalein is a natural indicator.
Explanation
Phenolphthalein is often used as an indicator in acid-base titrations. It will appear pink in basic solutions and clear in acidic solutions. Hence, phenolphthalein is chosen because it changes colour in a pH range between 8.3 – 10. But it is not a natural indicator.
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Q11:
Question for Assertion & Reason Type Questions: Acids, Bases and Salts
Try yourself:Assertion: HCl gas does not change the colour of dry blue litmus paper.
Reason: HCl gas dissolves in the water present in wet litmus paper to from H+ ions.
Explanation
Both assertion (A) and reason (R) are true, R is not the correct explanation of assertion (A).
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Q12:
Question for Assertion & Reason Type Questions: Acids, Bases and Salts
Try yourself: Assertion : HCl produces hydronium ions (H3O+) and chloride ions (Cl-) in aqueous solution.Reason : In presence of water, basic give H+ ions.
Explanation
Assertion (A) is true but reason (R) is false. HCl produces H+ ions in aqueous solution because in the presence of water, acids give H+ ions. As H+ ions cannot exist alone so it combines with water molecules and forms H3O+.
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Q13:
Question for Assertion & Reason Type Questions: Acids, Bases and Salts
Try yourself: Assertion: Sodium hydroxide reacts with zinc to produce hydrogen gas.Reason : Acids react with active metals to produce hydrogen gas.
Explanation
Sodium hydroxide being a strong base, reacts with active metal (zinc) to produce H2 gas. The reaction is given as follows
Zn (s) + 2NaOH (aq) → Na2ZmO2 (aq)+ H2 (g)
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Q14:
Question for Assertion & Reason Type Questions: Acids, Bases and Salts
Try yourself:Assertion : Ammonia solution is an alkali.
Reason : Ammonia solution turns blue litmus paper red.
Explanation
Ammonia gas, which is alkaline, turn the red litmus paper blue.
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Q15:
Question for Assertion & Reason Type Questions: Acids, Bases and Salts
Try yourself:Assertion : To dilute concentrated sulphuric acid water is added to the acid slowly.
Reason : A lot of heat energy will be given out in the dilution of concentrated sulphuric acid.
Explanation
Water is never added to concentrated sulphuric acid as it is an exothermic reaction and releases a large amount of heat energy. It also results in spurting of the acid, which can burn your skin. Concentrated sulphuric acid is added to water in small amounts and that too with constant stirring and cooling.
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