Environmental Chemistry II: Water: Solved Exercise and Think-Tank

Question 2: Give short answers.

I. List the impurities present in water 💧.

Answer.

1. Calciom bicarbonate (Ca(HCO3)2)

2. Magnesiumbicarbonate (Mg(HCO3)2)

3. Gypsum (CaSO4.2H2O) or anhydrous (CaSO4)

4. Kieserite (MgSO4.H2O)

ii. List toxic substances present in household 🏠 waste.

Answer.

1. Human waste

2. Livestock waste

3. Soaps and detergents

4. Paints and oil

5. Food and vegetables wastes

6. Garbadge

iii. In which ways, industrial waste pollute water.

Answer.

During manufacturing of industrial products, some by-products and waste effluents are also produced. These waste products may be in the form of waste heat, solid or waste water effluents. These waste may contain highly toxic compounds and heavy metals such as Pb, CD, Cr, Hg,As, Sb, etc. Industrial units generally discharge their wastes either to open land or into water bodies, lakes, ponds, rivers or oceans. Water from tanneries contains large quantity of Cr(VI) Salts.

iv. What is water pollution?

Answer.

Water pollution is the contamination of both surface and ground water by sufficient concentration of minerals, household waste, septic tanks, petroleum, natural gas and industrial wastes.

v. List some waterborne diseases.

Answer.

1. Cholera

2. Dysentery

3. Jaundice

4. Hepatitis

5. Typhoid

vi. What are pathogenic microorganisms?

Answer. These are organism that cause disease in host. These organisms are transmitted through food, water💧 and direct contact. These organism cause cholera, dysentery, jaundice, hepatitis and typhoid.

Question 3: What is hard water? Why is it sometimes undesirable?

Answer. A water that gives little lather or form scum with soap is called hard water. It is sometimes undesirable because:

It wastes a lot of soap when used for washing.

It forms scum with soap adhers to the clothes and can spoil the finish of some fabrics.

It causes kettles to fur.

It can cause hot 🔥 water 💧 pipes, boiler and car radiator to block due to formation of insoluble Salts of Ca and Mg.

Question 4: List two ways in which lakes and streams become polluted.

Answer.

1. Household waste

2. Industrial waste

Question 5:Give chemical equation for the

a. reaction of slaked lime with aluminium.

b. Carbonated rain water with lime stone.

c. Reaction that occurs when temporary hard water is boiled.

d. Ca2+ ions interact with Sodium zeolite.

Answer.

a. 3Ca(OH)2 + Al2(SO4)3 ----------> 2Al(OH)3 + 3CaSO4

b. CaCO3 + H2CO3 ------------> Ca(HCO3)3

c. M(HCO3)2 ---------------> MCO3 + CO2 + H2O

M = Ca, Mg

d. Ca2+ Na2Z -------------> CaZ + Na+

Question 6: How can buildings made of lime stone be affected by acid rain?

Question 7: Make a list a main methods of softening hard water. In each case write a chemical equation to summarise the chemical reactions involved.

Answer.

1. By Boiling

M(HCO3)2 -------------heat---------> MCO3 + CO2 + H2O

where M = Ca2+ , Mg2+

2. By adding slaked lime (Clark's method)

Ca((HCO3)2 + Ca(OH)2 ----------> CaCO3 + 2H2O

Mg(HCO3)2 + Ca(OH)2 --------------> CaCO3 + MgCO3 + 2H2O

By adding washing soda

Question 8: List some advantages of water hardness.

Question 9: What are on earth 🌎 four main water sources?

Question 10: How does hard water differ from the soft water?

Question 11: What is the purpose of coagulation in water treatment?

Question 12: Explain how hard water hampers the cleansing action of soap 🧼.

Question 13: Why are municipal water supplies treated with aluminium sulphate and slake lime?

Question 14: What are some health effects of biological contamination of water.

Question 15: Write a word and balanced chemical equation to show the effect of heat on magnesium hydrogen carbonate in an aqueous solution.

Think Tank

Question 16: Why is it cooler near a lake then inland during summer ?

Question 17: List two cations and 3 anions present in lake or surface water

Question 18: Why is it waste water chlorinated before it is return to the water body

Question 19: Hard water causes cattle to far this far can be removed by using an asset explain why ?

Question 20: Following chemical equation is about calcium compound.

Comp. A + Ca(OH(2 ----------> Comp. B + H2O

Comp. B + Ca(OH(2 ----------> Comp. C

Name and give the formula of compound A compound c

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