" AKC SCIENCE CLASSES"
CLASS 10 TH (CBSE AND MP BOARD)
"CHAPTER 02"
"ACIDS, BASES AND SALTS"
"EXERCISE QUESTION AND ANSWERS"
Q:-01:- A solution turns red litmus blue, its pH is likely to be
(a) 1 (b) 4 (c) 5 (d) 10
Ans:- (d) pH = 10.
Q:-02:- 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.
Q:-03:- 10ml 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.
Q:-04:- Which one of the following types of medicines is used for treating indigestion?
(a) Antibiotic (b) Analgesic
(c) antacid (d) Antiseptic.
Ans:- (c) Antacid.
Q:-05:- Write word equations and then balanced equations for the reation 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) Zinc +dil sulphuric acid ⟶ Zinc sulphate + hydrogen
Zn + H2SO4 ⟶ ZnSO4 + H2
(b) Magnisium ribbon + dil hydrochloric acid ⟶ Magnesium chloride + Hydrogen
Mg + 2HCl ⟶ MgCl2 + H2
(c) Aluminium powder + dil sulphuric acid ⟶ Aluminium sulphate + Hydrogen
2Al + 3H2SO4 ⟶ Al2(SO4)3 + 3H2
(d) Dilute hydrochloric acid + Iron filings ⟶ Iron chloride + Hydrogen
2Fe + 6HCl ⟶ 2FeCl3 + 3H2.
Q:-06:- Compounds such as alcohols and glucose also contain hydrogen but are not categorised as acids. Describe an Activity to prove it.
Ans:- Take solutions of alcohols, glucose in a beaker. Take a cork and fix two nails on the cork upto the end. Keep this cork in the beaker. Connect the nails to two terminals of a6 volt battery through a bulb and a switch. Switch on the current. You will see that bulb not glow or the current does not pass through the circuit. This means no ions or H+ ions are present in the solution. this shows that alcohols and glucose are not acids.
Q:-07:- Why does distilled water not conduct electricity, whereas rain water does?
Ans:- Rain water contains ions of acids and so it conducts electricity whereas there are no ions in distilled water.
Q:-08:- why do acids not show acidic behaviour in the absence of water?
Ans:- Acid in water give hydronium ions which are responsible for their acidic behaviour. But in the absence of water acids do not generate hydronium ions and thus do not show acidic behaviour.
Q:-09:- 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) strong alkaline?
(c) strongly acidic? (d) weakly acidic?
(e) weakly alkaline?
Arrange the pH in increasing order of hydrogen-ions concentration.
Ans:- (a) D (b) C (c) B (d) A (e) E
pH values in increasing order of hydrogen ions concentration:-
11 < 9 < 7 < 4 < 1.
Q:-10:- Equal lengths of magnesium ribbons are taken in test tubes A and B. Hydrochloric acid (HCl) is added to test tubes 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:- Fizzing will occur more vigorously in test tube A containing hydrochloric acid. This is because hydrochloric acid is stronger acid than acetic acid and reaction between Mg and acetic acid.
Q:-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:- pH of milk falls below 6 as it turns into curd due to the formation of lactic acid during this process.
Q:-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?
(b) Why does this milk take a long time to set as curd?
Ans:- (a) The milkman adds a little baking soda to fresh milk to make it slightly alkaline so that it can be preserved for a longer time.
(b) Initially lactic acid is formed is used up to neutralize the base i.e., baking soda and when more lactic acid is formed, the milk sets as curd.
Q:-13:- Plaster of Paris should be stored in a moister-proof container. Explain, why?
Ans:- Plaster of Paris is calcium sulphate hemihydrate (CaSO4.½H2O). On exposure to moister it absorbs moisture and becomes gypsum (CaSO4.2H2O) which does not have the required setting property.
Q:-14:- What is a neutralization reaction? Give examples.
Ans:- The reaction between an acid and a base to give salt and water is known as a neutralization reaction.
Base + Acid ⟶ Salt + Water
Examples:-
(Ñ–) HCl + NaOH ⟶ NaCl + H2O
(Acid) (Base) (Salt) Water
Hydrochloric Sodium Sodium
acid hydroxide chloride
(ⅱ) CH3COOH + NaOH ⟶ CH3COONa + H2O
(Acid) (Base) (Salt) Water
Q:-15:- Give two important uses of washing soda and baking soda.
Ans:- Uses of baking soda :-
(Ñ–) It is used in bakery.
(ⅱ) It s used in soda-acid fire extinguishers.
Uses of washing Soda :-
(Ñ–) It is used in the manufacturing of glass, soap and paper.
(ⅱ) It is used for the removing permanent hardness of water.
ACIDS, BASES AND SALTS || EXERCISE QUESTIONS AND ANSWERS || WITH COMPLETE EXPLANATIONS. CLICK HERE
