Acids, Bases and Salts — Questions & Answers

Sample questions from Acids, Bases and Salts

1. Q1. Rain is called acid rain when the pH of the rain water falls below

   • A.5.6✓
   • B.7.0
   • C.8.2
   • D.6.8
   Solution

   Dissolved oxides of sulphur and nitrogen lower rain water pH below 5.6, making it acid rain.

2. Q2. When an acid reacts with a metal, the gas evolved is:

   • A.Carbon dioxide, which turns lime water milky
   • B.Oxygen, which relights a glowing splint
   • C.Hydrogen, which burns with a pop sound✓
   • D.Chlorine, which bleaches litmus
   Solution

   C is correct: the general reaction is acid plus metal giving a salt and hydrogen, and the pop test with a burning splint is what identifies the gas. A is given when an acid meets a carbonate or a hydrogencarbonate, not a metal. B is not produced by this reaction at all. D is produced only in special cases and not by the general reaction.

3. Q3. Baking powder contains baking soda and a mild edible acid so that:

   • A.CO₂ is produced without leaving a strongly alkaline taste✓
   • B.chlorine is produced
   • C.pH becomes exactly 14
   • D.salt cannot dissolve
   Solution

   The acid neutralises sodium carbonate formed and helps release CO₂.

4. Q4. The acid present in vinegar is:

   • A.acetic acid✓
   • B.hydrochloric acid
   • C.sulphuric acid
   • D.nitric acid
   Solution

   Vinegar contains dilute acetic acid.

5. Q5. In the given figure, the gas collected from the reaction of zinc granules with dilute sulphuric acid is tested with a burning candle and burns with a pop sound. The gas is

   • A.Carbon dioxide
   • B.Sulphur dioxide
   • C.Hydrogen✓
   • D.Oxygen
   Solution

   A pop sound with a burning splint is the standard confirmatory test for hydrogen gas.

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