Solution of Chapter 2. Acids, Bases and Salts (NCERT - Science Book)

You have been provided with three test-tubes. One of them contains distilled water and the other two contain an acidic solution and a basic solution, respectively. If you are given only red litmus paper, how will you identify the contents of each test-tube?

Why should curd and sour substances not be kept in brass and copper vessels?

Which gas is usually liberated when an acid reacts with a metal? Illustrate with the help of an example. How will you test the presence of this gas?

Metal compound A reacts with dilute hydrochloric acid to produce effervescence. The gas evolved extinguishes a burning candle. Write a balanced chemical equation for the reaction if one of the compounds formed is calcium chloride.

Why do HCl, HN0₃ etc., show acidic character in aqueous solutions while solutions of compounds like alcohol and glucose do not show acidic character?

Why does an aqueous solution of an acid conduct electricity?

Why does dry HCl gas not change the colour of dry litmus paper?

While diluting an acid, why is it recommended that the acid should be added to water and not water to the acid?

How is the concentration of hydronium ions (H₃Q⁺) affected when the solution of an acid is diluted?

How is the concentration of hydroxide ions (OH^-) affected when excess of base is dissolved in a solution of sodium hydroxide?

You have two solutions A and B. The pH of solution A is 6 and pH of solution B is 8. Which solution has more hydrogen ion concentration? Which of these is acidic and which one basic?

What effect does the concentration of H⁺(aq) ions have on the nature of the solution?

Do basic solutions also have H⁺(aq) ions? If yes, then why are these basic?

Under what soil condition do you think a farmer would treat the soil of his fields with quicklime (calcium oxide) or slaked lime (calcium hydroxide) or chalk (calcium carbonate)?

What is the common name of the compound CaOCl₂?

Name the substance which on treatment with chlorine yields bleaching powder.

Name the sodium compound which is used for softening hard water.

What will happen if a solution of sodium hydrogen carbonate is heated? Give the equation of the reaction involved.

Write an equation to show the reaction between Plaster of Paris and water.

A solution turns red litmus blue, its pH is likely to be:

A solution reacts with crushed egg-shells to give a gas that turns lime water milky. The solution contains:

10 ml of a solution of NaOH is found to be completely neutralised by 8 ml of a given solution of HCI. If we take 20 ml of the same solution of NaOH, the amount of HCl solution (the same solution as before) required to neutralize it will be:

Which one of the following types medicines is used for treating indigestion?

Write word equations and then balanced equations for the reactions taking place when:

(a) dilute sulphuric acid reacts with zinc granules

(b) dilute hydrochloric acid reacts with magnesium ribbon

(c) dilute sulphuric acid reacts with aluminium powder

(d) dilute hydrochloric acid-reacts with iron filings

Compounds such as alcohol and glucose also contain hydrogen but are not categorized as acids. Why? Describe an activity to prove it.

Why does distilled water not conduct electricity whereas rain water does?

Why do acids not show acidic behaviour in the absence of water?

Five solutions A, B, C, D and E when tested with universal indicator showed pH as 4, 1, 11, 7 and 9 respectively.

(a) Which solution is (i) neutral (ii) strongly alkaline (iii) strongly acidic (iv) weakly acidic, and (v) weakly alkaline?

(b) Arrange the pH values in the increasing order of hydrogen ion concentration.

Equal lengths of magnesium ribbons are taken in test-tubes A and B. Hydrochloric acid (HCI) is added to test-tube A while acetic acid (CH₃COOH) is added to test-tube B. In which test-tube will the fizzing occur more vigorously and why?

Fresh milk has a pH of 6. How do you think the pH will change as it turns into curd? Explain your answer.

A milkman adds a very small amount of baking soda to fresh milk.

(a) Why does he shift the pH of the fresh milk from 6 to slightly alkaline?

(b) Why does this milk take a longer time to set as curd?

Plaster of Paris should be stored in a moisture-proof container. Explain why?

What is a neutralization reaction? Give two examples.

Give two important uses each of washing soda and baking soda.