Acids, Bases, Salts, Indicators and pH

Question 1

What is an acid defined as when dissolved in water?

Accepted Answer

A substance that produces hydrogen ions $ (H^+) $

Question 2

What color change occurs when blue litmus paper is exposed to an acid?

Accepted Answer

It turns red

Question 3

When an acid reacts with an active metal like zinc, which gas is produced?

Accepted Answer

Hydrogen gas

Question 4

Which of the following equations represents the preparation of an acid by direct combination of elements?

Accepted Answer

$ H_2(g) + Cl_2(g) \rightarrow 2HCl(g) $

Question 5

What are the products when hydrochloric acid reacts with calcium carbonate?

Accepted Answer

Calcium chloride, water, and carbon dioxide

Question 6

Which acid is commonly used in car batteries and acts as an industrial dehydrating agent?

Accepted Answer

Sulfuric acid $ (H_2SO_4) $

Question 7

What is a base defined as when dissolved in water?

Accepted Answer

A substance that produces hydroxide ions $ (OH^-) $

Question 8

What is a water-soluble base called?

Accepted Answer

An alkali

Question 9

Which reaction represents the preparation of a base by reacting an active metal with water?

Accepted Answer

$ 2Na(s) + 2H_2O(l) \rightarrow 2NaOH(aq) + H_2(g) $

Question 10

When a base is heated with an ammonium salt, which gas is liberated?

Accepted Answer

Ammonia gas $ (NH_3) $

Question 11

What color does phenolphthalein indicator turn in a basic solution?

Accepted Answer

Pink/red

Question 12

What is a neutralisation reaction?

Accepted Answer

A reaction between an acid and a base to form salt and water

Question 13

A solution has a pH of 3. How is this solution classified?

Accepted Answer

Acidic

Question 14

How do farmers typically adjust highly acidic soils to ensure optimal crop growth?

Accepted Answer

By adding lime (calcium hydroxide)

Question 15

What is a salt?

Accepted Answer

An ionic compound formed when the hydrogen ion of an acid is replaced by a metal or ammonium ion

Question 16

Which method is best suited for preparing an insoluble salt like barium sulfate $ (BaSO_4) $?

Accepted Answer

Precipitation (Double Decomposition)

Question 17

Why is sodium hydrogen sulfate $ (NaHSO_4) $ classified as an acidic salt?

Accepted Answer

It contains replaceable hydrogen ions from a partially neutralized polybasic acid

Question 18

What is a deliquescent substance?

Accepted Answer

A substance that absorbs moisture from the air and dissolves in it to form a solution

Question 19

Which of the following is an example of an efflorescent substance that loses its water of crystallisation when exposed to air?

Accepted Answer

Washing soda $ (Na_2CO_3 \cdot 10H_2O) $

Question 20

According to general solubility rules, which of the following salts is insoluble in water?

Accepted Answer

Barium sulfate $ (BaSO_4) $

Strong work.