Following questions consist of two statements – Assertion (A) and Reason (R). Answer these questions selecting the appropriate option given below:
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
Q.1. Assertion (A) : The acid must always be added to water with constant stirring.
Reason (R) : Mixing of an acid with water decreases the concentration of H+ ions per unit volume.
Q.2. Assertion (A) : Copper sulphate crystals are wet because it contains water of crystallisation.
Reason (R) : Water of crystallisation is the fixed number of molecules of water present in one
formula unit of salt.
Q.3. Assertion (A) : The aqueous solutions of glucose and alcohol do not show acidic character.
Reason (R) : Aqueous solutions of glucose and alcohol do not give H+ ions.
Q.4. Assertion (A) : HCl gas does not change the colour of dry blue litmus paper.
Reason (R) : HCl gas dissolves in the water present in wet litmus paper to form H+ ions.
Q.5. Assertion (A) : Weak acids have low electrical conductivity.
Reason (R) : Strong acids and weak acids have equal concentration of hydrogen ions in their solutions.
Q.6. Assertion (A): Pure water is neither acidic nor basic.
Reason (R) : The pH of a solution is inversely proportional to the concentration of hydrogen
ions in it.
Q.7. Assertion (A) : During electrolysis of concentrated aqueous solution of sodium chloride, hydrogen is produced at anode and chlorine gas is produced at cathode.
Reason (R) : Ions get attracted to oppositely charged electrodes.
Q.8. Assertion (A) : Baking powder is used in making cake instead of using only baking soda.
Reason (R) : Baking powder contains tartaric acid which reacts with sodium carbonate and removes bitter taste.
Q.9. Assertion (A) : The chemical formula of bleaching powder is CaOCI.
Reason (R) : Calcium oxide reacts with chlorine to form bleaching powder.
Q.10. Assertion (A): Plaster of Paris is stored in a moisture proof container.
Reason (R) : Plaster of Paris sets into a hard mass on wetting with water to form anhydrous calcium sulphate.
Q.11. Assertion (A): The chemical name of bleaching powder is calcium oxychloride.
Reason (R): Bleaching powder is used as an oxidising agent in chemical industries.
Q.12. Assertion: The process of dissolving an acid or a base in water is highly exothermic reaction.
Reason: Water must always be added slowly to acid with constant stirring.
AnswerAnswer: (a) The process of dissolving an acid or a base in water is highly exothermic reaction. Acid must always be added slowly to water with constant stirring.
Q.13. Assertion : Phenolphthalein is an acid-base indicator.
Reason: Phenolphthalein gives different colours in acidic and basic medium.
Q.14. Assertion: Calcium sulphate hemihydrate, CaSO4.1/2 H20 is called plaster of Paris.
Reason: Plaster of Paris is used for producing moulds for pottery and ceramics and casts of statues.
Q.15. Assertion : pH = 7 signifies pure water.
Reason: pH of acetic acid is greater than 7.
AnswerAnswer: (c) pH of acetic acid is less than 7.
Q.16. Assertion : HCl is a stronger acid than acetic acid.
Reason: On dissociation, HCl yields lesser hydrogen ions for the same concentration as compared to acetic
AnswerAnswer: (c) On dissociation, HCl yields more hydrogen ions for the same concentration as compared to acetic acid.
Q.17. Assertion : pH of ammonium nitrate solution is acidic.
Reason: Solution of a salt of weak base and strong acid is acidic.
AnswerAnswer: (a) Ammonium nitrate is a salt of ammonium hydroxide (weak base) and nitric acid (strong acid).
Q.18. Assertion : Phosphoric acid is a weak acid.
Reason : Phosphoric acid when dissolved in water dissociates partially and produces very little H* ions.
Q.19. Assertion : Antacids neutralize the effect of extra acid produced in the stomach during indigestion and thus provide relief.
Reason: Antacids are mild bases.
Q.20. Assertion : Acetic acid does not act as an acid in benzene solution.
Reason: Benzene is non-polar.
AnswerAnswer: (a) For ionization of an acid, polar solvents (like water) are required. As ionization does not take place in non-polar solvents (like benzene) so acetic acid does not acts as an acid.
Q.21. Assertion : Bleaching powder reacts with dilute acids to evolve chlorine.
Reason: The chlorine liberated by the action of dilute acids on bleaching powder is called available chlorine.
Q.22. Assertion : Sodium carbonate pentahydrate is also known as washing soda.
Reason: Chief raw materials for the manufacture of washing soda are NH3, NaCl and CaCO3.
Q.23. Assertion: Common salt is used for the preparation of many chemicals such as sodium hydroxide, bleaching powder, baking soda, washing soda etc.
Reason : Main source of sodium chloride is sea water.
Q.24. Assertion : AlCl3 is a basic salt.
Reason: AlCl3 is a salt of strong acid and a weak base.
Q.25. Assertion : Baking soda is prepared by chlor-alkali process.
Reason: Brine decomposes to sodium hydroxide on passing electricity through it.
Q.26. Assertion : Salt of KNO3 is formed by strong base and weak acid.
Reason: Salt of NH4Cl is formed by weak base and strong acid.
Q.27. Assertion : Strength of the acid or base decreases with dilution.
Reason: Ionization of an acid or a base increases with dilution.
Q.28. Assertion : Higher the H ion concentration, lower is the pH value.
Reason: The pH of a neutral solution=7, that of a basic solution < 7 and that of an acidic solution > 7.
Q.29. Assertion : CH3COOH is used as vinegar in cooking and food preservatives.
Reason: Strong acids are those acids which ionise almost completely in aqueous solution and hence produce a large amount of Hions.
Q.30. Assertion : Tooth decay starts when the pH of the mouth is lower than 5.5.
Reason: Enamel starts corroding below 5.5 pH.