Studymates91

NCERT Solutions for class 10 Science Ch.2 Acids Bases and Salts 

NCERT Solutions for class 10 Chapter 2 Acids, bases and salts is prepared for the purpose of  clearing all doubts about this chapter and it's ncert exercise question to help the students to score high marks in their CBSE board examination. In this ncert solution we try to explain every answers in easy and simple ways.To score better marks in class 10 science examination students should get well versed with the NCERT Solutions provided here.

science class 10.

Qu.1 A solution turns red litmus blue, its pH is likely to be

a) 1  (b) 4 (c) 5  (d) 10

Ans. d)10

Qu.2 A solution reacts with crushed egg-shells to give a gas that turns lime-water milky. The solution contains.

a) NaCl  (b) HCl (c) LiCl   (d) KCl

Ans. b)HCl

Qu.3 10 mL of a solution of NaOH is found to be completely neutralised by 8 mL of a given solution of HCl. If we take 20 mL of the same solution of NaOH, the amount HCl solution (the same solution as before) required to neutralise it will be

(a) 4 mL   (b) 8 mL (c) 12 mL   (d) 16 mL

Ans. d) 16 mL

Qu.4 Which one of the following types of medicines is used for treating indigestion?

(a) Antibiotic   (b) Analgesic (c) Antacid   (d) Antiseptic

Ans. (c) Antacid

Qu.5 Write word equations and then balanced equations for the reaction 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.

Ans. a) Word equation :- Dilute sulphuric acid + Zinc → Zinc Sulphate + Hydrogen Gas

 Balanced equation :- H2SO4(aq) + Zn → ZnSO4(aq) + H2(g)

b) Word equation :- Dilute Hydrochloric + Magnesium → Magnesium Chloride + Hydrogen Gas

 Balanced equation :- 2HCl(aq) + Mg → MgCl2(aq) + H2(g)

(c) Word equation :- Dilute Sulphuric Acid + Aluminium → Aluminium Sulphate + Hydrogen Gas

Balanced equation :- 3H2SO4(aq) + 2Al(s) → Al2(SO4)3(aq) + 3H2(g)

(d) Word equations :- Dilute Hydrochloric Acid + Iron → Ferrous Chloride + Hydrogen Gas

Balanced equation :- 6HCl(aq) + 3Fe(s) → 3FeCl2(aq) + 3H2(g)

Qu.6 Compounds such as alcohols and glucose also contain hydrogen but are not categorised as acids. Describe an Activity to prove it.

Ans. Alcohol (ethyl alcohol) has the formula C2H5OH and glucose has the formula C6H12O6

Thus, both of them contain hydrogen but they are not categorised as acids. The following activity can be carried out to prove it.

Activity.

Materials required : Beaker, rubber cork, nails, 6 V battery, connecting wires, bulb, switch,

ethyl alcohol

Procedure :

1. Set up the apparatus as shown in Figure.

2. Take ethyl alcohol in the beaker such that the upper ends of the nail remain 2 cm above

the level of alcohol.

3. When the switch is turned on, we observe that the bulb does not glow.

4. Repeat the experiment by taking glucose solution in place of alcohol. Again, we observe

that the bulb does not glow.

This shows that the flow of current does not take place in both the cases. This proves that

there are no H+ ions in alcohol and glucose solution, as electricity is conducted through the ions(H+ ions) in solution.

Qu.7 Why does distilled water not conduct electricity, whereas rain water does?

Ans. Rain water contains small amounts of acid(H+ ions) because of which it conducts electricity. Distilled water is pure water. It contains no traces of H+ ions. Therefore,it does not conducts electricity.

Qu.8 Why do acids not show acidic behaviour in the absence of water?

Ans. Acids produce H+ ions or H3O+ ions only in the presence of water. In the absence of water, hydronium ions are not produced.They show no acidic behaviour in the absence of water.

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

(a) neutral?

(b) Strongly alkaline?

(c) Strongly acidic?

(d) Weakly acidic?

(e) Weakly alkaline?

Ans. 

Solutions	pH	Nature
A B C D E	4 1 11 7 9	Weakly acidic Strongly acid Strongly alkaline Neutral Weakly alkaline

Qu.10 Equal lengths of magnesium ribbons are taken in test tubes A and B. Hydrochloric acid (HCl) is added to test tube A, while acetic acid (CH3COOH) is added to test tube B. Amount and concentration taken for both the acids are same. In which test tube will the fizzing occur more vigorously and why?

Ans. HCl is stronger acid than acetic acid. Therefore, H+ ion concentration in test tube A will be more than that in test tube B. Hence, reaction will take place faster in test tube A than in test tube B. In other words,fizzing will occur more vigorously in test tube B.

Qu.11 Fresh milk has a pH of 6. How do you think the pH will change as it turns into curd? Explain your answer.

Ans. Yes, the bacteria change the fresh milk into curd producing lactic acid and because of the lactic acid in curd,the pH will come down from 6 to a lower value.

Qu.12 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?

Ans. He shift the pH of fresh milk from 6 to slightly alkaline on addition of a very small amount of baking soda to prevent the milk from souring.

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

Ans. Lactic acid formed as a result of fermentation is neutralised by baking soda. This prolongs the time take by a milk to set as curd.

Qu.13 Plaster of Paris should be stored in a moisture-proof container. Explain why?

Ans. Plaster of Paris is a white powder and when it comes in contact of water and  moisture,it changes to gypsum (a hard solid mass).Therefore the Plaster of Paris is stored in moisture-proof container to prevent it from this kind of change.

Qu.14  What is a neutralisation reaction? Give two examples.

Ans. The reaction between an acid and a base to give their respective salts and water as a product is known as neutralisation reaction.

Qu.15 Give two important uses of washing soda and baking soda.

Ans. The two important usage of Washing soda are:-

i) It is used in glass,soap and paper industries.

ii) It is used for removing permanent hardness of water.

The two important usage of Baking soda are :-

i) It is used in soda-acid fire extinguishers

ii) It is used as an ingredient in antacids.