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Practice each question, then open the answer or worked solution.
What happens when a solution of an acid is mixed with a solution of a base in a test tube?
(a) (i) only
(b) (i) and (iii)
(c) (ii) and (iii)
(d) (i) and (iv)
The answer is (d) (i) and (iv)
Explanation:
When acid is mixed with a solution of base it results in a neutralization reaction. Neutralization is an exothermic reaction which results in the formation of salt.
An aqueous solution turns red litmus solution blue. Excess addition of which of the following solution would reverse the change?
The answer is (d) Hydrochloric acid
Explanation:
If the solution turns red litmus to blue colour then the solution should be basic in nature. Its effect can be neutralized by adding an acid hence (d) Hydrochloric acid is the answer.
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
The answer is (c) absorb moisture from the gas
Explanation:
Calcium is a good dehydrating agent. It has the property to absorb moisture. Hence it is used as a desiccant to dry gases and Hydrocarbons in the industries.
Which of the following salts does not contain water of crystallisation?
The answer is (b) Baking soda
Explanation
Baking sodas is white amorphous powder whereas other salts given in the question are crystalline in nature.
Sodium carbonate is a basic salt because it is a salt of
The answer is (d) weak acid and strong base
Explanation:
Salt formed by weak acid and strong base form strong salt. Here, Sodium is a strong base and carbonate is a weak acid.
Calcium phosphate is present in tooth enamel. Its nature is
The answer is (a) basic
Explanation:
Phosphate ion present in calcium phosphate is a strong base and it forms a strong salt. Hence, calcium
phosphate is basic in nature.
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?
The answer is (d) An antacid
Explanation:
Sample solution turn pH paper yellowish-orange which confirms the acidic nature of the sample. To make the colour to greenish-blue, we have to add an antacid.
Which of the following gives the correct increasing order of acidic strength
The answer is a) Water < Acetic acid < Hydrochloric acid
Explanation:
Water is neutral in its pure form, Acetic acid is an organic acid which is weak in nature and Hydrochloric acid is a strong acid.
If a few drops of a concentrated acid accidentally spills over the hand of a student, what should be done?
The answer is (b) Wash the hand immediately with plenty of water and apply a paste of sodium hydrogen carbonate
Explanation:
Washing affected hand with plenty of water will reduce the concentration of the acid. Remaining traces of the acid can be neutralized by applying a paste of Hydrogen carbonate which is basic in nature. Though NaOH is also a base but it is corrosive in nature hence it is not used to neutralize the acid.
Sodium hydrogen carbonate, when added to acetic acid, evolves a gas. Which of the following statements are true about the gas evolved?
(a) (i) and (ii)
(b) (i), (ii) and (iii)
(c) (ii), (iii) and (iv)
(d) (i) and (iv)
The answer is (a) (i) and (ii)
Explanation:
Reaction between Sodium hydrogen carbonate and acetic acid leads to the evolution of carbon-dioxide gas. CO2 turns the lime water milky and extinguish a burning splinter.