CBSE Class 10 Science Acids bases and salts Sure Shot Questions B

CBSE Class 10 Science Acids bases and salts Sure Shot Questions B. Please refer to the examination notes which you can use for preparing and revising for exams. These notes will help you to revise the concepts quickly and get good marks.

ACIDS, BASES AND SALTS

Short Answer Questions

Question. What is a neutralization reaction? Give an examples.
Answer : A reaction in which an acid and base react with each other to give a salt and water is termed as neutralization reaction. In this reaction, energy is evolved in the form of heat.
(i) NaOH + HCl → NaCl + H₂O
(Base) (Acid) (Salt) (Water)
(ii) During indigestion (caused due to the production of excess of hydrochloric acid in the stomach),
we administer an antacid (generally milk of magnesia, which is basic in nature). The antacid neutralizes the excess of acids and thus gives relief from indigestion.
Example- 
Mg (OH)₂ + 2HCl→ MgCl₂ + 2H₂O

Question. Give two important uses of washing soda and baking soda.
Answer : Two important used of washing soda and baking soda are as follows:
(1) Washing soda:
(a) It is used in glass, soap, and paper industries.
(b) It is used to remove permanent hardness of water.
(2) Baking soda:
(a) It is used as baking powder. Baking powder is a mixture of baking soda and a mild acid known as tartaric acid. When it is heated or mixed in water, it releases CO₂ that makes bread or cake fluffy.
(b) It is used in soda-acid fire extinguishers.

Question. What will be the action of the following substances on litmus paper?
Dry HCl gas, Moistened NH3 gas, Lemon juice, Carbonated soft drink, Curd, Soap solution.
Answer : Substance            Action on Litmus paper
Dry HCl gas                          No change
Moistened NH3 gas              Turns red to blue
Lemon juice                          Turns blue to red
Carbonated soft drink           Turns blue to red
Curd                                      Turns blue to red
Soap solution                        Turns red to blue

Question. Name the acid present in ant sting and give its chemical formula. Also give the common method to get relief from the discomfort caused by the ant sting.
Answer : The acid present in ant sting is Methanoic acid (formic acid). The chemical formula is
HCOOH. To get relief one should apply any available basic salt e.g., baking soda (NaHCO3) on it.

Question. What happens when nitric acid is added to egg shell? Write suitable chemical reaction.
Answer : Egg shells contain calcium carbonate. When nitric acid is added to it, carbon dioxide gas is evolved. The reaction can be given as
CaCO₃ + 2HNO₃ → Ca (NO₃)₂ + H₂O + CO₂

Question. A student prepared solutions of (i) an acid and (ii) a base in two separate beakers. She forgot to label the solutions and litmus paper is not available in the laboratory. Since both the solutions are colourless, how will she distinguish between the two?
Answer : Using chemical indicator like phenolphthalein or natural indicators like turmeric, china rose

Question. How would you distinguish between baking powder and washing soda by heating?
Answer : The chemical formula of baking powder is Sodium Hydrogencarbonate (NaHCO₃). Whereas, that of washing soda is sodium carbonate (Na₂CO₃.10H₂O)
Sodium hydrogencarbonate on heating gives CO₂ gas which will turn lime water milky whereas no such gas is obtained from sodium carbonate.

Question. Name the acid present in ant sting and give its chemical formula. Also give the common method to get relief from the discomfort caused by the ant sting.
Answer : The acid present in ant sting is methanoic acid (formic acid).
The chemical formula is HCOOH.
To get relief one should apply any available basic salt e.g., baking soda (NaHCO₃) on it.

Question. What is water of crystallisation ? give two examples
Answer : Water of crystallisation is the fixed number of water molecules present in one formula unit of a salt. Examples- CuSO₄.5H₂O, CaSO₄.2H₂O

Question. Write the formula and give one use of each of the following compounda.
Plaster of Paris
b. Bleaching powder
c. Baking soda
Answer : a. CaSO₄ 1/2 H₂O, used to join fractured bones
b. CaOCl₂ , used to disinfect water
c. NaHCO₃ , making food items crispy and fluffy

Long Short Answer Questions

Question. Salt A commonly used in bakery products on heating gets converted into another salt B which itself is used for removal of hardness of water and a gas C is evolved. The gas C when passed through lime water, turns it milky due to formation of D. Identify A, B , C and d. write equation to show formation of D from C
Answer : Baking powder (NaHCO₃), salt A is commonly used in bakery products. On heating it forms sodium carbonate (Na₂CO₃), B and CO₂ gas, C is evolved.
When CO₂ gas is passed through lime water it forms calcium carbonate (CaCO₃), which is slightly soluble in water making it milky.
A — NaHCO₃ B — Na₂CO₃ C — CO₂ gas D- CaCO₃
CO2 + Ca (OH)₂ → CaCO₃ + H₂O

Question. In one of the industrial processes used for manufacture of sodium hydroxide, a gas X is formed as by product. The gas X reacts with lime water to give a compound Y which is used as a bleaching agent in chemical industry. Identify X and Y giving the chemical equation of the reactions involved.
Answer : In the manufacture of sodium hydroxide, hydrogen gas and chlorine gas (X) are formed as by–products. When chlorine gas (X) reacts with lime water, it forms calcium oxychloride (bleaching powder) Y. The reactions are -
2NaCl (aq) + 2H₂O (l) → 2NaOH (aq) + Cl₂ (g) + H₂ (g) X→ Cl₂ (Chlorine gas)
Ca (OH)₂ (s) + Cl₂ (g) → CaOCl₂ (s) + H₂O
Y — Calcium oxychloride (bleaching powder)

Question. Match the following pH values 1, 7, 10, 13 to the solutions given below:
• Milk of magnesia
• Gastric juices
• Brine
• Aqueous Sodium hydroxide.
Amit and Rita decided to bake a cake and added baking soda to the cake batter. Explain with a balanced reaction, the role of the baking soda. Mention any other use of baking soda.
Answer : • Milk of magnesia 10
• Gastric juices 1
• Brine 7
• Aqueous Sodium hydroxide 13
Baking soda undergoes thermal decomposition to form Na₂CO₃ ,CO₂ and H₂O ; CO₂ makes the cake fluffy & soft

Uses: Used in fire extinguishers/ antacid to neutralize excess acid in stomach / to neutralize the effect of acid in insect sting.

Question. (i) Four samples A, B, C and D change the colour of pH paper or solution to Green, Reddishpink, Blue and Orange. Their pH was recorded as 7, 2, 10.5 & 6 respectively. Which of the samples has the highest amount of Hydrogen ion concentration? Arrange the four samples in the decreasing order of their pH.
(ii) Rahul found that the Plaster of Paris, which he stored in a container, has become very hard and lost its binding nature. What is the reason for this? Also, write a chemical equation to represent the reaction taking place.
(iii) Give any one use of Plaster of Paris other than for plastering or smoothening of walls.
Answer : (i) a) B
b) C,A,D,B
(ii) Due to moisture in the atmosphere it converted into Gypsum
CaSO₄ + 1½ H₂O → CaSO₄.2H₂O
(iii) Making toys/dolls or statues /fixing broken limbs/making decorative materials.

Question. A dry pellet of a common base B, when kept in open absorbs moisture and turns sticky.
The compound is also a by–product of Chlor alkali process. Identify B
What type of reaction occurs when B is treated with an acidic oxide? Write a balanced chemical equation for one such solution.
Answer : B is Sodium hydroxide (NaOH) is a commonly used base and is hygroscopic, that is, it absorbs moisture from the atmosphere and becomes sticky.
The acidic oxides react with base to give salt and water.
The reaction between NaOH and CO₂ can be given as
2 NaOH + CO₂ → Na₂CO₃ + H₂O

MCQs

1. The colour of neutral litmus solution is

a) red (b) blue (c) purple (d) yellow

2. Which of the following indicators is an olfactory indicator?

(a) litmus (b) vanilla (c) turmeric (d) phenolphthalein

3. Which one is suitable method to find the accurate pH value?

(a) pH meter (b) pH paper (c) Universal indicator (d) Litmus solution

4. Which one of the following statements is correct about universal indicator?

(a) It is a mixture of HCl and NaOH

(b) It is a mixture of many indicators

(c) It is a solution of phenolphthalein in alcohol

(d) It is a solution of phenolphthalein in water.

5. Which of the following properties are shown by dilute HCl?

(1) It turns blue litmus red

(2) It turns red litmus blue

(3) It reacts with zinc and a gas is evolved

(4) It reacts with solid sodium carbonate to give brisk effervescence

(a) 1 and 2 (b) 1 and 3 (c) 1, 3 and 4 (d) 2, 3 and 4

6. A teacher gave two test tubes – one containing water and the other containing sodium hydroxide solution to two students. Then he asked them to identify the test tube containing sodium hydroxide solution. Which one of the following can be used for correctly identifying the test tube containing the solution of sodium hydroxide?

(a) Blue litmus (b) Red litmus (c) Sodium carbonate solution (d) Dilute HCl

7. Metallic oxides are ________ in nature, but non-metallic oxides are __________ in nature.

The information in which alternative completes the given statement?

(a) neutral, acidic (b) acidic, basic (c) basic, neutral (d) basic, acidic

8. When a drop of unknown solution X is placed on a strip of pH paper, a deep red colour is produced. This sample is which one of these?

(a) NaOH (b) HCl (c) Water (d) CH₃COOH

9. A student tests a sample drinking water and reports its pH value as 6 at room temperature. Which one of the following might have been added in water?

(a) Calcium chloride (b) Sodium chloride (c) Sodium bicarbonate (d) Bleaching powder

10. Solid sodium bicarbonate was placed on a strip of pH paper. The color of the strip

(a) turned red (b) did not change (c) turned green and slightly yellow (d) turned pink

11. Four drops of red litmus solution were added to each of the following samples. Which one turns red litmus blue?

(a) Alcohol (b) Distilled water (c) Sodium hydroxide sol (d) HCl

12. The pH of which of the following samples can not be found directly using pH paper?

(a) Lemon juice (b) Dilute HCl (c) Solid sodium bicarbonate (d) Solution of a detergent.

13. Which of the following natural sources contains oxalic acid?

(a) lemon (b) orange (c) tomato (d) tamarind

14. The acid found in an ant sting is

(a) acetic acid (b) citric acid (c) tartaric acid (d) methanoic acid

15. To relieve pain caused due to acidity, we can take
(a) sour milk (b) lemon juice (c) orange juice (d) milk of magnesia

16. What are the products obtained when potassium sulphate reacts with barium iodide in an aqueous medium?

(a) KI and BaSO₄ (b) KI, Ba and SO₂ (c) K, I2 and BaSO₄ (d) K, Ba, I2 and SO₂

17. Which of the following salts is basic in nature?

(a) NH4NO₃ (b) Na2CO₃ (c) Na2SO₄ (d) NaCl

18. Which of the following salts has the minimum pH value?

(a) (NH4)2SO₄ (b) NaHCO₃ (c) K2SO₄ (d) NaCl

19. You are given four unknown solutions I, II, III, and IV. The pH values of these solutions are found to be 3, 7, 8, and 10 respectively. Among the given solutions, which solution has the highest hydrogen ion concentration?

(a) I (b) II (c) III (d) IV

20. Which one of the following is required to identify the gas evolved when dilute hydrochloric acid reacts with zinc metal?

(a) blue litmus paper (b) red litmus paper (c) a burning slinter (d) lime water

21. Zinc reacts with an acid as well as with a base to liberate hydrogen. On the basis of this what should be the nature of the zinc metal?

(a) basic (b) acidic (c) amphoteric (d) neutral

22. When you test the solutions of sodium bicarbonate, sodium hydroxide, hydrochloric acid and acetic acid with universal indicator, in which case would you get a red colour?

(a) sodium bicarbonate (b) hydrochloric acid (c) sodium hydroxide (d) acetic acid

23. The pH of a sample of pure water is 7 at room temperature. What is its pH when a pinch of solid sodium bicarbonate is dissolved in it?

(a) vary near to 7 (b) less than 7 (c) more than 7 (d) exactly 7

24. If an unknown solution turns blue litmus red, then the pH of the solution is more likely to be

(a) 12 (b) 10 (c) 7 (d) 4

25. What is the pH of a 0.00001 molar HCl solution?

(a)1 (b)9 (c)5 (d)4

26. There are alternate acid base theories that define an acid as any species that can {hint: According to Bronsted-Lowry theory, an acid is any species that can donate a proton
to another species.}

(a) donate a proton (2) donate an electron (c) accept a proton (d) accept an electron

27. What happens when a solution of an acid is mixed with a solution of a base in a test tube?

(i) The temperature of the solution increases

(ii) The temperature of the solution decreases

(iii) The temperature of the solution remains the same

(iv) Salt formation takes place

(a) (i) only (b) (i) and (iii)

(c) (ii) and (iii) (d) (i) and (iv)

28. An aqueous solution turns red litmus solution blue. Excess addition of which of the following solution would reverse the change?

(a) Baking powder

(b) Lime

(c) Ammonium hydroxide solution

(d) Hydrochloric acid

29. During the preparation of hydrogen chloride gas on a humid day, the gas is usually passed through the guard tube containing calcium chloride. The role of calcium chloride taken in
the guard tube is to

(a) absorb the evolved gas

(b) moisten the gas

(c) absorb moisture from the gas

(d) absorb Cl– ions from the evolved gas

30. Compounds such as alcohols and glucose contain hydrogen but are not categorized as acids. Describe an activity to prove it.

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

32. Why do acids not show acidic behavior in the absence of water?

33. 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 Arrange the pH in increasing order of hydrogen ion concentration.

34. What is a neutralization reaction? Give two examples.

35. What happens when an acid or base is mixed with water?

36. Equal lengths of magnesium ribbons are taken in test tubes A and B. Hydrochloric acid is added to test tube A, while acetic acid is added to test tube B. The concentrations taken for both the acids are same in which test tube the reaction occur more vigorously and why?

37. Fresh milk has a pH of 6. How does the pH change as it turns to curd? Explain your answer.

38. 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?

39. Why does tooth decay start when the pH of mouth is lower than 5.5?

40. How does the flow of acid rain water into a river make the survival of aquatic life in a river difficult?

41. Dry hydrogen chloride gas does not turn blue litmus whereas hydrochloric acid does. Why?

42. What is meant by “water of crystallization” of a substance? Describe an activity to demonstrate water of crystallization.

43. Plaster of paris should be stored in a moisture – proof container. Explain why?

44. What is baking powder? How does it make the cake soft and spongy?

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

46. WHO AM I?

• I can roughly measure pH value from 0-14.

• I am called antichlor and am used to remove excess chlorine from clothes when treated with bleaching powder.

• I am a product of gypsum and am used to making chalks and fire proof materials.

• I am a compound of calcium and can be used for disinfecting drinking water as well as for decolourisation.

• I give different smell in acid and base solution.

• I am an oxide capable of showing properties for both acids and bases.

• I am a covalent compound and conducts electricity in aqueous medium.

• I am a salt of potassium hydroxide and nitric acid.

• I am the term used when a solid becomes liquid when exposed to moist air.

•I am derived from tomato and turn blue litmus into red.

47. The colour of methyl orange indicator in acidic medium is: ( )

a) Yellow b) green c) orange d) red

48. The colour of phenolphthalein indicator in basic solution is: ( )

a) Yellow b) green c) pink d) orange

49. What is the colour methyl orange in alkaline medium? ( )

a) orange b) yellow c) red d) blue

50. A solution turns red litmus blue, its pH will be: ( )

a) 1 b) 4 c) 5 d) 10

51. 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

52. Why is universal indicator a better one than litmus paper? ( )

a) Litmus paper can only be used for acids.

b) Litmus paper can only be used for alkalis.

c) Universal indicator goes green if something is neutral.

d) Universal indicator is useful for all ranges of pH of the solution.

53. Water soluble bases are known as? ( )

a) neutral b) base c) acid d) alkali

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