Matric Notes Chemistry 10th Chapter 15 Environmental Chemistry-II Water Exercise Short Questions

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Exercise Short Questions

Q1. How does water rise in plants?

Ans. Water rises in plants by capillary action. Capillary action is the process by which water rises up from the roots of plants to leaves. This process is vital for the survival of the land plants.

Q2. Which forces are responsible for dissolving polar substances in water?

Ans. Dipole forces are responsible for dissolving substances in water because water is a polar solvent. Positive end of polar substance is attracted by negative end of water while negative end of polar molecule is attracted by positive end of water molecule.

Q3. Why are non-polar compounds insoluble in water?

Ans. Non-polar compounds like benzene, ether, etc. have covalent bonds. They do not have polar ends. So non-polar compounds are not attracted by water molecules.

Q4. How does water dissolve sugar and alcohols?

Ans. Sugar and alcohols have hydroxyl group (O-∂ -- H+∂ ) having polar ends. These substances are soluble in water due to hydrogen bonding which is possible due to the polar O∂- and H∂+ ends of water.

Q5. How does limestone dissolve in water?

Ans. Limestone (CaCO₃) is insoluble in water but small quantity of limestone is soluble in water in the presence of CO₂. It is shown as:

CaCO₃ + CO₂ + H₂O ---> Ca(HCO₃)₂

Q6. Differentiate between soft and hard water.

Ans. Soft Water

1. It is that water which produces good lather with soap.
2. It does not give curd.
3. It is free from Ca(2+) or Mg(+2) ions.

Hard Water

1. It is that type of water which does not produce good lather with soap.
2. It gives curd with soap.
3. It contains Ca(+2) or Mg(+2) ions.

Q7. What are the causes of hardness in water?

Ans. The rain water while coming down dissolves carbon dioxide from the atmosphere. While passing through the beds of soil rain water dissolves many salts of divalent cations like Mg(2+), Ca(2+), and anions like Cl(1-), SO₄(2-), HCO₃(1-) and CO₃(2-). For example, gypsum (CaSO₄).2H₂O) and (CaCO₃) . These salts make the water hard.

Q8. What are effects of temporary hardness in water?

Ans. Effects of temporary hardness

1. It consumes large amount of soap in washing purposes.
2. Temporary hard water causes stomach disorder.
3. Insoluble calcium and magnesium carbonates present in hard water not only reduce the efficiency of the engine, but also cause the boiler to burst.

Q9. Mention the disadvantages of detergents.

Ans. Disadvantages of detergents

1. They make water unfit for aquatic life.
2. They cause diseases due to the presence of microbes in such water.
3. The phosphate salts present in detergents cause rapid growth of algae. These plants ultimately die and decay by consuming oxygen gas present in water which results in death of aquatic life.

Q10. What is the difference between bio-degradable and non-bio-degradable substances?

Ans. Those substances that can be decomposed by microorganisms like bacteria are called bio-degradable substances and those substances that cannot be decomposed by microorganisms like bacteria are called non-bio-degradable.

Q11. How do detergents make the water unfit for aquatic life?

Ans. Phosphate salts present in detergents cause rapid growth of algae in water bodies, which floats over the surface of water. These plants die and decay. Decaying plants consume oxygen gas present in water. Thus depletion of oxygen gas leads to death of aquatic life.

Q12. Why are pesticides used?

Ans. Pesticides are used to kill or control the growth of pests. Pests may be weeds, herbs, fungi and viruses, which damage crops and transmit diseases both to humans beings and animals.

Q13. What are the reasons of water borne diseases?

Ans. Diseases that spread because of drinking polluted water or eating food prepared with polluted water are called water borne infectious diseases. Microorganisms like viruses, bacteria, protozoa and worms present in water cause water borne diseases.

Q14. How can water borne diseases be prevented?

Ans. Prevention from water borne diseases:

Water borne diseases can be prevented by taking the following measures:

• Provision of safe water: Drinking water must be properly treated and purified.
• Disposal of sewage: There must be adequate sanitary disposal of sewage. Any type of waste must not be thrown or discharged directly in water suppliers or reservoirs.
• Control of toxic chemicals: Chemical contamination can cause acute illness, but often toxic contaminants are slow poisons and carcinogens. There must be a strict control over the use of pesticides and other chemicals.