$Ca(HCO_3)_2 \xrightarrow{\text{boiling}} CaCO_3 + CO_2 + H_2O$

Question 1

Which physical property of water allows ice to float on liquid water, and what is its significance for aquatic life?

Accepted Answer

Anomalous expansion; it ensures that ice forms on the surface, insulating aquatic life below.

Question 2

Which equation correctly represents the removal of temporary hardness by boiling?

Accepted Answer

$Ca(HCO_3)_2 \xrightarrow{	ext{boiling}} CaCO_3 + CO_2 + H_2O$

Question 3

Which process is primarily responsible for the natural purification of water in the water cycle?

Accepted Answer

Evaporation and condensation

Question 4

What is the main cause of permanent hardness in water?

Accepted Answer

Presence of magnesium sulfate and calcium chloride

Question 5

Which method is most effective for removing permanent hardness from water?

Accepted Answer

Ion exchange resin

Question 6

A sample of water contains $Ca^{2+}$ and $Mg^{2+}$ ions. Which chemical equation represents the removal of these ions using sodium zeolite?

Accepted Answer

$Na_2Z + Ca^{2+} \rightarrow CaZ + 2Na^{+}$

Question 7

Which of the following is NOT a consequence of water hardness?

Accepted Answer

Increased corrosion of pipes

Question 8

Which process is used to obtain distilled water in laboratories?

Accepted Answer

Distillation using Liebig condenser

Question 9

What is the chemical composition of water?

Accepted Answer

$H_2O$

Question 10

Which of the following is a major source of water pollution?

Accepted Answer

Industrial effluents

Question 11

Which property of water is directly proportional to external pressure?

Accepted Answer

Boiling point

Question 12

Which of the following is a disadvantage of hard water?

Accepted Answer

It causes scale formation in boilers

Question 13

Which process is used to remove suspended impurities from river water?

Accepted Answer

Sedimentation

Question 14

What is the role of photosynthesis in the water cycle?

Accepted Answer

It provides oxygen and supports aquatic life

Question 15

Which equation represents the electrolysis of water?

Accepted Answer

$2H_2O \rightarrow 2H_2 + O_2$

Question 16

Which of the following is a method for removal of permanent hardness?

Accepted Answer

Addition of washing soda ($Na_2CO_3$)

Question 17

Which source of water is most suitable for drinking after proper treatment?

Accepted Answer

Surface water from rivers

Question 18

What is the main reason for the depletion of the water table in urban areas?

Accepted Answer

Over-extraction of groundwater

Question 19

Which of the following is NOT a use of distilled water?

Accepted Answer

For drinking purposes

Question 20

Which process is used to purify water by removing both suspended and dissolved impurities?

Accepted Answer

Distillation

Chapter 5: Water – Properties, Sources, Uses, and Chemistry

Study Guide - Practice Questions