1. Percentage of sodium chloride in sea water is

a. 0.02
b. 3.4
c. 97
d. 2

2. Density of water is maximum at

a. 0^oC
b. 4^oC
c. 100^oC
d. -4^oC

3. Which salt does not cause water to become hard

a. calcium hydrogen carbonate
b. magnesium hydrogen carbonate
c. magnesium sulphate
d. sodium chloride

4. Which salt causes temporary hardness in water

a. magnesium sulphate
b. calcium sulphate
c. both calcium sulphate and magnesium sulphate
d. magnesium hydrogen carbonate

5. Heating calcium hydrogen carbonate produces

a. CO2
b. H2O
c. CaCO3
d. All

6. Which of following is not a water borne disease

a. hepatitis
b. typhoid
c. dysentry
d. anemia

7. Which human activity results in contamination of water bodies

a. livestock waste
b. pesticides
c. septic tanks
d. all of these

8. Which is used to remove permanent hardness in water

a. slaked lime
b. washing soda
c. boiling water
d. all of these