Acid Base and Salt

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

• Baking powder
• Lime
• Ammonium hydroxide solution
• Hydrochloric acid
  Answer: (d) Hydrochloric acid

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

• absorb the evolved gas
• moisten the gas
• absorb moisture from the gas
• absorb Cl⁻ ions from the evolved gas
  Answer: (c) absorb moisture from the gas

Which of the following salts does not contain water of crystallisation?

• Blue vitriol
• Baking soda
• Washing soda
• Gypsum
  Answer: (b) Baking soda

Sodium carbonate is a basic salt because it is a salt of

• strong acid and strong base
• weak acid and weak base
• strong acid and weak base
• weak acid and strong base
  Answer: (d) Weak acid and strong base

Calcium phosphate is present in tooth enamel. Its nature is

• basic
• acidic
• neutral
• amphoteric
  Answer: (c) neutral

A sample of soil is mixed with water and allowed to settle. The clear supernatant solution turns the pH paper yellowish-orange. Which of the following would change the colour of this pH paper to greenish-blue?

• Lemon juice
• Vinegar
• Common salt
• An antacid
  Answer: (d) An antacid

Which of the following gives the correct increasing order of acidic strength?

• Water < Acetic acid < Hydrochloric acid
• Water < Hydrochloric acid < Acetic acid
• Acetic acid < Water < Hydrochloric acid
• Hydrochloric acid < Water < Acetic acid
  Answer: (a) Water < Acetic acid < Hydrochloric acid

If a few drops of a concentrated acid accidentally spills over the hand of a student, what should be done?

• Wash the hand with saline solution
• Wash the hand immediately with plenty of water and apply a paste of sodium hydrogencarbonate
• After washing with plenty of water apply solution of sodium hydroxide on the hand
• Neutralise the acid with a strong alkali
  Answer: (b) Wash the hand immediately with plenty of water and apply a paste of sodium hydrogen carbonate.

Sodium hydrogencarbonate when added to acetic acid evolves a gas. Which of the following statements are true about the gas evolved?

• It turns lime water milky
• It extinguishes a burning splinter
• It dissolves in a solution of sodium hydroxide
• It has a pungent odour

• (i) and (ii)
• (i), (ii) and (iii)
• (ii), (iii) and (iv)
• (i) and (iv)
  Answer: (a) (i) and (ii)