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Class 10 Science Chapter 2: Acids, Bases and Salts MCQs with answers

10 multiple-choice questions on Acids, Bases and Salts, each with its answer and the reason, written from the NCERT chapter. Open a question's solution to check your working; then take the free test to find your next chapter.

Question 1
Two drops of phenolphthalein are added to four colourless liquids. The liquid that turns pink is
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Answer: (b) sodium hydroxide solution

Phenolphthalein is pink in a basic solution and colourless in an acidic one. Only sodium hydroxide solution is basic; the other three are acidic.

Question 2
Litmus solution is added to a sample that is neither acidic nor basic. The colour of the litmus is
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Answer: (c) purple

Litmus solution is purple when the solution is neither acidic nor basic; red and blue are its colours in acid and in base.

Question 3
Which of the following is a synthetic indicator?
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Answer: (c) Methyl orange

Methyl orange is made synthetically. Turmeric, red cabbage extract and litmus are obtained from natural sources.

Question 4
Ananya drops zinc granules into dilute sulphuric acid and brings a burning splint near the mouth of the test tube. She observes that
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Answer: (d) the gas burns with a pop sound

An acid and a metal give a salt and hydrogen gas. Hydrogen burns with a pop sound when a burning splint is brought near it.

Question 5
Carbon dioxide turns lime water milky. The milkiness is due to the formation of
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Answer: (b) calcium carbonate

Carbon dioxide reacts with calcium hydroxide to form calcium carbonate, which is insoluble and makes the lime water milky. Calcium hydrogencarbonate is soluble.

Question 6
The pH of a solution changes from 8 to 13. This means that
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Answer: (a) the hydroxide ion concentration has increased

A rise in pH from 7 towards 14 is a rise in hydroxide ion concentration, so the alkali has become stronger.

Question 7
Milk of magnesia, taken to relieve acidity, is
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Answer: (a) Mg(OH)₂

Milk of magnesia is magnesium hydroxide, Mg(OH)₂, a mild base that neutralises excess stomach acid.

Question 8
Rain water collected in an industrial town has a pH of 4.8. Which statement about it is correct?
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Answer: (d) It is acid rain, and its flow into rivers lowers the pH of the river water.

Rain water with a pH below 5.6 is acid rain. Flowing into rivers it lowers their pH and makes survival of aquatic life difficult, which rules out option (b).

Question 9
Which of the following is NOT a use of bleaching powder?
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Answer: (a) Supporting fractured bones in the right position

Bleaching powder bleaches cotton and linen, disinfects drinking water and serves as an oxidising agent. Supporting fractured bones is a use of Plaster of Paris.

Question 10
The chemical name of baking soda is
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Answer: (d) sodium hydrogencarbonate

Baking soda is sodium hydrogencarbonate, NaHCO₃. Sodium carbonate is formed from it on heating, and sodium chloride is one of its raw materials.

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