Pttb board chemsitry class 10 notes chapter number 15 pdf download long short answer questions, multiple choices questions, and MCQs.
10th class chemistry solved exercises chapter 11 pdf Download
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PTTB BOARD CHEMSITRY NOTES CLASS 10 CHA 15 PDF Contains solved exercises, review questions, MCQs, important board questions and chapter overview.
Explain the methods of removing permanent hardness.
Answer:
Methods to remove permanent hardness
Permanently hard water cannot be softened by boiling. It can be removed by using chemicals. Calcium (Ca2+) and magnesium (Mg2+) are removed as insoluble salts by adding washing soda or zeolite.
i) By using washing soda
Calcium and magnesium ions present in hard water react with sodium carbonate to produce insoluble carbonates. The water then contains soluble and harmless sodium salts.
Na2CO3 + CaSO4 → CaCO3 + Na2SO4
Na2CO3 + MgSO4 → MgCO3 + Na2SO4
ii) By using sodium zeolite
Sodium zeolite is a naturally occurring resin of sodium aluminium silicate Naal(SiO3)2, but it can be prepared artificially as well. It is insoluble in water and has the property of exchanging ions present in them with the ions present in the solution. Hard water is passed through a container filled with resin containing sodium ions. Sodium zeolites exchange their Na+ ions with Ca2+, Mg2+, present in hard water.
Na2 zeolite + CaSO4 → Ca zeolite + Na2SO4
After the resin is fully used, it can be regenerated by flushing it with a concentrated solution of NaCl.
Ca zeolite + 2NaCl → Na2 zeolite + CaCl2
Q.3) Explain water pollution because of industrial waste.
Answer:
Industrial units are set up to produce the desired substances (chemicals, cloth, leather goods, rubber items, petrochemicals, and plastic items) on large scale. But manufacturing of industrial products are always accompanied by some by-products and waste effluents. Many industrial facilities use freshwater to carry away waste from the plant and into rivers, lakes and oceans. This is called industrial effluent. The industrial effluent may contain highly toxic compounds, mineral acids, oil and greases, and heavy metals such as Pb, Cd, Cr, Hg, As etc.
When these effluents enter the lakes, streams, rivers or oceans, they either dissolve in or float suspended in water. Pollutants from industrial sources include:
- (i) Nitrates and Phosphates: They can cause eutrophication, which can be a problem to marine environments.
- (ii) Sulphur: This is a non-metallic substance that is harmful for marine life.
- (iii) Oils: Oil does not dissolve in water; instead it forms a thick layer on the water surface. This can stop marine plants receiving enough light for photosynthesis. It is also harmful for fish and marine birds.
- (iv) Petrochemicals: This is formed from gas or petrol and can be toxic to marine life.
- (v) Heavy metals: cadmium, lead, and mercury are toxic and health hazards for human beings. Acute cadmium poisoning may result in high blood pressure, kidney damage and red blood cells destruction. Acute lead poisoning may result in dysfunction of kidney, liver, brain and reproductive system. Mercury poisoning causes neurological damage.
Justify the statement: household water is the reason of water pollution.
Answer:
Household wastes include human wastes, livestock wastes, soaps and detergents, food and vegetable wastes, garbage etc. Detergents are used in large amounts for cleaning purposes in houses because they have strong cleaning action than soap. But detergents are non-biodegradable i.e. they cannot be decomposed by microorganisms like bacteria.
When household water containing non-biodegradable detergents is discharged in streams, rivers and lakes, they remain in the water for a long time and make the water unfit for aquatic life. The phosphate salts present in detergents cause the rapid growth of algae in the water. These plants die and decay. As decaying plants are biodegradable, they consume the oxygen gas present in the water. As result oxygen depletes in the water. Aquatic animals feel suffocated and ultimately die due to an insufficient supply of oxygen.
Domestic sewage, including food and vegetable waste, garbage, cans, bottles etc, contains a wide variety of dissolved and suspended impurities. All these substances add to water pollution. Chemical and bacterial contents in household water can contaminate surface and underground water. Bacterial content may cause infectious diseases such as cholera, hepatitis, jaundice, dysentery, typhoid etc.
These facts show that household water is one of the reasons for water pollution.
Explain agricultural effluents are fatal for aquatic life.
Answer:
Fertilizers and pesticides play a major role in water pollution due to agricultural waste. Fertilizers are used to make up the deficiency of nitrogen, phosphorus etc of the soil due to large cultivation of crops in the recent years.
Pesticides are used in agriculture to control weeds, insect infestation and diseases, which damage crops and transmit diseases both to humans and animals.
Agricultural effluents have dual effects:
i) Chemicals from fertilizers and pesticides seep into the groundwater when intensive cultivation of crops is done. This is called leaching process. The irrigation run-off from agricultural fields releases high contents of nitrate in groundwater.
ii) Run-off from the agricultural fields where fertilizers and pesticides have been used enters into ponds, streams or rivers. This water contains nitrate (NO3–) and phosphate (PO43-) salts. These salts cause rapid growth of algae, floating over the surface of water. They prevent the sunlight and oxygen to reach the aquatic plants and animals. These plants die and decay. As decaying plants are biodegradable, they consume the oxygen gas present in the water. Thus, the depletion of oxygen results in death of aquatic life.
Explain five important waterborne diseases. How can these be prevented?
Answer:
The most important waterborne diseases are as follows:
(i) Cholera
Cholera is an acute diarrheal infection caused by ingestion of food or water contaminated with the bacterium Vibrio cholera, which may be found in water contaminated by human faeces. Â It is characterized by vomiting and purging.
(ii) Dysentery
Dysentery is an infection of the intestines that causes diarrhoea containing blood or mucous. Dysentery is typically caused by certain bacteria or parasites. The causative organism is frequently found in water polluted with human faeces, and is transmitted by faecal contamination of water or food.
(iii) Hepatitis
Hepatitis is an acute inflammation of the liver caused by one of five viruses called hepatitis A, B, C, D and E. Hepatitis A and E spread through polluted water.
(iv) Jaundice
Jaundice is a yellowish discolouration of the skin, eyes and mucous membranes. Excess of bile form liver enters the blood and causes yellowness of skin and eyes. The symptoms of jaundice may indicate damage to the liver in adults.
(v) Typhoid
Typhoid fever is a life-threatening intestinal disease caused by the bacterium Salmonella Typhi. It is spread by contaminated water or food prepared with contaminated water.
Prevention of waterborne diseases
Waterborne diseases can be prevented by taking the following measures:
(i) Ensuring that the drinking water is properly treated and purified.
(ii) Keeping control over the use of pesticides and other chemicals.
(iii) Not throwing or discharging the waste directly in water supplies or reservoirs.
