CBSE Class 10 Science Chapter-2 Acids, Bases and Salts Important Questions – Free PDF Download
Free PDF download of Important Questions with Answers for CBSE Class 10 Science Chapter 2 – Acids, Bases and Salts prepared by expert Science teachers from latest edition of CBSE(NCERT) books only by CoolGyan to score more marks in CBSE board examination.
CBSE Class 10 Science Acids, Bases and Salts Chapter-2 Important Questions
CBSE Class 10 science Important Questions Chapter 2 – Acids, Bases and Salts
3 Mark Questions
1. (a) Name the raw materials used is the manufacture of sodium carbonate by Solvay process?
(b) How is sodium hydrogen carbonate from a mixture of 
Ans. (a) Raw materials used are – 
lime stone or 
and 
(b) Sodium hydrogen carbonate 
is sparingly soluble or less soluble in water and it gets separated as a precipitate while NH4Cl remains in solution. This precipitate is removed by filtration.
2. Write equations for the following reactions
(i) Dilute sulphuric acid reacts with zinc granules
(ii) Dilute hydrochloric acid reacts with magnesium ribbon.
(iii) Dilute sulphuric acid reacts with aluminum powder.
Ans. (i) 
(ii) 
(iii) 
3. (a) An aqueous solution has a PH value of 7.0. Is this solution acidic, basic or neutral?
(b) If H+ concentration of a solution is 
mol 
what will be its P4 value?
(c) Which has higher PH value: 
or 
Ans. (a) The solution is neutral is nature
(b) 
(c) 1 M NaOH solution (basic) higher PH. Value
1 M HCl solution (acidic) lower PH. Value
4. What will you observe when:
(i) Red litmus is introduced into a solution of sodium sulphate.
(ii) Methyl orange is added to dil HCl.
(iii). Blue litmus is introduced into a solution of ferric chloride
Ans. (i) It will undergo any colour change because solution of Na2SO4 is water is almost neutral.
(ii) In the acidic solution, the colour of methyl Orange will change to reddish.
(iii) FeCl3 solution on reacting with water will form ferric hydroxide and hydrochloric acid. Since the acid is strong, the solution will be acidic. Therefore the colour of blue litmus will change to red.
5. A first aid manual suggests that vinegar should be used to treat wasp sting and baking soda for bee stings.
(a) What does this information tell you about the chemical name of the wasp sting?
(b) If there were no baking soda in the house, what other house hold substances would you use to treat as stings?
Ans. (a) The chemical present in the sting must be base because vinegar (acetic acid) is used to heal or neutralize the effect of wasp stings.
(b) Since bee stings are treated by backing soda which is a base it means they must contain some acid. If baking soda is not available in the house, solution of ammonium hydroxide NH4OH can be used for the same purpose.
6. Does Tartaric acid helps in making cake or bread fluffy. Justify.
Ans. No, tartaric acid does not evolve any carbon dioxide during baking. Its role is to react with Na2CO3 formed when NaHCO3 decomposes.
If this not happens, Na2CO3 will impart a bitter taste to the cake.
7. Explain why?
(a) Common salt becomes sticky during the rainy season.
(b) Blue vittriol change to white upon heating.
Ans. (a) Common salt contains impurity of magnesium chloride (MgCl2) which is of deliquescent nature. When exposed to atmosphere, it becomes moist. Therefore common salt becomes sticky during the rainy season.
(b) Blue vitriol (CuSO4 5H2O) during heating changes to a anhydrous copper sulphate (CuSo4) which is white in colour.
8. A compound X of sodium is commonly used in kitchen for making crispy pakoras. It is also used for curing acidity in the stomach. Identify ‘X’. What is its chemical formula? State the reaction that takes places when it is heated during cooking?
Ans. Compound X is a constitute of baking powder. It is also called as baking soda. Chemically, the compound is sodium hydrogen carbonate with formula NaHCO3. Upon heating the compound X releases CO2 gas
2NaHCO3 (s) 
Na2CO3 (s) + H2O (l) + CO2 (g)
9. Explain why-
(i) Anhydrous calcium chloride is used in desiccators
(ii) If bottle full of concentrated 
is left open in the atmosphere by accident, the acid starts flowing out the bottle of its own.
Ans. (a) Anhydrous calcium chloride 
is highly hygroscopic in nature it readily absorbs moisture and is therefore used as drying agent.
(b) Concentrated sulphuric acid is highly hygroscopic it absorbs moisture from air and gets diluted. Since the volume increases, the acid starts flowing out of the bottle.
10. How is plaster of Paris chemically different from gypsum? How may these be inter converted? Write one use of plaster of Paris?
Ans. Plaster of Paris is different from Gypsum as it is prepared from heating gypsum. Plaster of Pairs is a major constituent of surgical bandages used for setting fractured bones. Before applying on fractured bone, it is made wet with water and as a result of hydration it changes into gypsum which keeps the bones in position.
These may be interconverted by the reaction.
The use of plaster of Paris are-
(i) It is used for making modules or casts for toys pottery, ceramics etc.
(ii) In surgical bandages for setting fractured bones.
11. (a) What is the action of red litmus on
(i) Dry ammonia gas
(ii) Solution of ammonia gas is water?
(b) State the observations you would make on adding ammonium hydroxide to aqueous solution of
(i) furious sulphate
(ii) Aluminium chloride?
Ans. (a) (i) Red Litmus has no action on dry ammonia gas. Because it does not release any hydroxyl ions 
(ii) When it is passed through water 
is converted to ammonia hydroxide 
It dissociates to give hydroxyl ions 
and the solution is basic in nature. Red litmus acquires a blue colour.
(b) (i) A green precipitate of ferrous hydroxide will be formed by double decomposition reaction.
(ii) A white precipitate of aluminum hydroxide will be formed by double decomposition reaction
12. State the chemical property in each case on which the following uses of baking soda are based
(i) As an antacid
(ii) As a constituent of baking powder.
Give the chemical for baking soda
Ans. (i) It is weakly alkaline is nature and neutralizes acid 
formed is the stomach. 
(ii) It evolves 
in the form of bubbles when cake is made by baking. As a result, the cake becomes porous as well as fluffy.
The chemical formula of baking soda is 
13. Metal compound ‘A’ reacts with dilute hydrochloric acid to produce efferenvescence. The gas evolved extinguishes a burning candle. Write a balanced chemical equation for the reaction, if one of the compounds formed is calcium chloride.
Ans. As one of the compounds formed is calcium chloride, metal compound ‘A’ is salt of calcium.
Burning candle is extinguished by carbon dioxide so carbon dioxide gas is produced by reaction of ‘A’ with hydrochloric acid.
Carbon dioxide is produced by action of HCl on carbonate that means ‘A’ is calcium carbonate.
CaCO3 + HCl 
CaCl2 + CO2 + H2O
14. Why do HCl, HNO3 etc. show acidic characters in aqueous solution while solutions of compounds like alcohol and glucose do not show acidic character?
Ans. Compounds like HCl and HNO3 release hydrogen ions in solution, therefore they shows acidic character.
While compounds like alcohol and glucose do not release hydrogen ions. Therefore they do not show acidic properties.
15. 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 ions concentration? Which is acidic and which one is basic?
Ans. A solution having pH less than 7 is acidic and that having pH more than 7 is basic. So, solution ‘A’ is acid and ‘B’ is basic. Naturally ‘A ‘which is acidic has greater concentration of hydrogen ions concentrations.
16. Under what soil condition do you think a farmer would treat the soil of his field with quicklime (calcium oxide) or slaked lime (calcium hydroxide) or chalk (calcium carbonate).
Ans. The farmer would treat the soil of his field with quicklime (calcium oxide) or slaked lime (calcium hydroxide) or chalk (calcium carbonate) when field has become acidic to neutralize the effect of acid.
17. Under what soil condition do you think a farmer would treat the soil of his field with quicklime (calcium oxide) or slaked lime (calcium hydroxide) or chalk (calcium carbonate).
Ans. The farmer would treat the soil of his field with quicklime (calcium oxide) or slaked lime (calcium hydroxide) or chalk (calcium carbonate) when field has become acidic to neutralize the effect of acid.
18. A milkman adds a very small amount of baking soda to fresh milk.
(a) Why does he shift the pH of the milk from 6 to slightly alkaline?
(b) Why does this milk take a long time to set a curd?
Ans. (a) The pH of milk changes from 6 to slightly alkaline on addition of a very small amount of baking soda. This is because sodium hydrogen carbonate (baking soda) is basic in nature. This prevents the milk from souring.
(b) Lactic acid formed as a result of fermentation is neutralized by sodium hydrogen carbonate. This prolongs the time taken by milk to set as curd.
19. What is a neutralization reaction? Give two examples.
Ans. The reaction between an acid and a base to give salt and water is called neutralization reaction.
For example:
NaOH + HCl NaCl + H2O
KOH + HNO3 KNO3+ H2O
20. Give two important uses of washing soda and baking soda.
Ans. Uses of washing soda:
(i) As cleansing agent.
(ii) Removing permanent hardness of water.
(iii) Used in glass, soap and paper industries.
Uses of baking soda:
(i) For making baking powder.
(ii) As ingredient of antacid.
21. Compound P forms enamel of teeth. It is the hardest substance of the body. It does not dissolve in water but it is corroded when pH in the mouth is below 5.5. How does tooth paste prevent dental decay?
Ans. P =
Bacteria present in the mouth produce acids by degradation of sugar And food particles remaining in the mouth after eating. Using toothpastes, which Are generally basic, for cleaning the teeth can neutralize the excess acid and prevent Tooth decay.
22. The oxide of a metal M was water soluble when a blue litmus strip was dipped in
This solution, it did not go any change in colour. Predict the nature of oxide.
Ans. The Metal oxide (MO) is of basic in nature. It dissolve in water to form metal
Hydroxide as 
Blue litmus does not undergo any change in Colour in the basic medium.
23. A road tanker carrying an acid was involved in an accident and its contents spilled on the road, iron drain covers began melting and fizzing as the acid ran over them. A Specialist was called to se if the acid actually leaked into the nearby river.
(a) Explain how the specialist could carry out a simple test to see if the river water contains some acid or not.
(b) The word melting is incorrectly used in the report. Suggest a better name that should have been used.
(c) Explain why drain covers began fizzing as the acid rain over them.
Ans. (a) By dipping a strip of blue limos paper in to the sample of river water. If the colour Changes to red this means that some acid has gone in to the river.
(b) Corrosion.
(c) Iron reacts with acid to evolve hydrogen gas.
24. A compound ‘A’ on heating at 370 K gives ‘B’ used as plaster for supporting fractured Bones in the right position. ‘B’ on mixing with water changes to ‘A’. Identify ‘A’ and ‘B’ And write the chemical reaction.
Ans.
25. A student heated a few crystals of copper sulphate n a dry boiling tube.
(a) What will be the color of the copper sulphate after heating?
(b) Will you notice water droplets in the boiling tube?
(c) Where have these come from
Ans. (a) White
(b) Yes
(c) Copper sulphate crystals which seem to be dry contain water of crystallization.