Water New Simplified Class-9 Dalal ICSE Chemistry Solutions

by Dr Viraf J Dalal Middle School Chemistry Allied Publishers

Water New Simplified Class-9 Dalal ICSE Chemistry Solutions Chapter-3.  We Provide Step by Step Solutions of Exercise/Lesson -3 Water with Additional Questions , Previous Year Questions and Unit Test-3 of Dr Viraf J Dalal Middle School Chemistry Allied Publishers. Visit official Website CISCE for detail information about ICSE Board Class-9.

Water New Simplified Class-9 J Dalal ICSE Dr Viraf Chemistry Solutions Chapter-3


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Previous Year Question

Additional Questions

Unit Test Questions


Previous Year Questions of Chapter-Water for ICSE Class-9 Chemistry

Question 1.(1984)

Name one substance which is ‘deliquescent’.
Answer:
Deliquescent substance is NaOH (sodium hydroxide), KOH, CaCl2

Question 2.(1984)

How does an increase in temperature affect :

  1. the solubility of NaCl
  2. the solubility of CaSO4 in water ?

Answer:
Increase in temperature :

  1. Increases the solubility of NaCl only a little.
  2. Solubility of CaSO4 first increases and then decreases.

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Question 1.(1985)

Give reasons for the following :
  1. table salt becomes moist and sticky during the rainy season
  2. a white power forms on the surface of washing soda crystals which are left exposed to the air.

Answer:

  1. Table salt contains impurities of calcium and magnesium chloride which are Deliquescent and absorb moisture from air and common salt becomes Sticky and Wet During humid conditions [rainy season].
  2. Washing Soda is Efflorescent substance when exposed to air loses its moisture [water of crystallisation partly and becomes powder which forms white powder on the crystals.

Question 1.(1986)

Name a salt

(a) which contain of crystallization
(b) which does not contain.

Answer:

(a) Blue vitriol [copper sulphate] CuSO4. 5H2O
(b) Potassium chloride KCl or sodium chloride NaCl

Question 1.(1987)

Name a deliquescent substance’.
Answer:
Iron [III] chloride [FeCl3]

Question 1.(1988)

Explain the following observations :
  1. Washing-soda become coated with a white powder when left exposed to the atmosphere.
  2. In the expression anhydrous copper sulphate, what is meant by “anhydrous”.
  3. Why is fused calcium chloride or cone, sulphuric acid used in a desiccator.

Answer:

  1. Washing Soda : is efflorescent substance and lose its water of crystallisation partly when exposed to atmosphere and change into white powder (amorphous state).
  2. Copper sulphate loses water of crystallization when heated and becomes white powder of CuSO4. This white powder (CuSO4) without water is anhydrous.
  3. Fused CaCl2 or cone. H2SO4 is used in desiccator as drying agent to remove moisture from the substance (to dry it) but does not change its composition.

Question 2.(1988)

Complete the following : The solubility of a gas at constant pressure may be increased by decreasing the
Answer:
The solubility of a gas at constant pressure may be increased by decrease in temperature.

Question 1.(1991)

What is ‘water of crystallization’ ? Name a crystalline salt which does not contain water of crystallization.
Answer:
Water Of Crystallization : “The fixed number of water molecules which enter into a loose Chemical Combination with the substance when the substance is crystallised from its hot saturated solution is called water of crystallization.”
The substance is crystalline but does not contain water of crystallization is KCl

Question 2.(1991)

What would you observe, when the water of crystallization of a salt Is removed by heating it.
Answer:
It will turn Amorphous in nature lose its Geometric shape, become powder.

Question 3.(1991)

Define :

  1. Hygroscopy
  2. Efflorescence.

Answer:

  1. Hygroscopy : “is the phenomenon of a subtance to absorb water (moisture) from the atmosphere but does not change its state.”
  2. Efflorescence : “Is the phenomenon in which a substance loses it moisutre (water of crystallisation partly or completely to atomsphere and change to amorphous state, when exposed to atmosphere.”

Question 4.(1991)

What is the effect of temperature on the solubility of KNO, and calcium sulphate in water.
Answer:
Solubility of KNO3 increases with temperature and solubility of calcium sulphate first increases upto 50°C and then decreases upto 100°C.

Question 1.(1992)

What test would you do to find out whether a given solution is saturated or unsaturated.
Answer:
If on adding more of solute in the given solution and stirring, the solute dissolves, it is unsaturated solution. If the solute settles down and does not dissolve, it is saturated solution.

Question 2.(1992)

How can you increase the solubility of a given volume of gas in water.
Answer:
Solubility of a given volume of gas can be increased by increasing the pressure on the surface of water.

Question 1.(2007)

Define ‘eutrophication’.
Answer:
Eutrophication : “Organic matter in sewage poured into water bodies generally results in excessive growth of algae – which deoxygenates water and produces deadening atmosphere there.”

Question 2.(2007)

What is meant by the term ‘oil spill’.
Answer:
Oil spill or Leaks : Oil is lighter and insoluble in water and oil layer floats on the surface of water and prevents oxygen transfer from atmosphere.
Oil leakage and petroleum products into sea water due to accidents of ships and oil tankers or leakage of pipe lines and storage tanks. They occur when oil is being produced from offshore well and may happen due to transportation by pipes and tanks, oil refineries, petrochemical plants etc.
Damage caused by oil spills :

  1. Fish, birds, reptiles and amphibians living in such water cannot breathe and die. The oil penetrates the birds feathers and they cannot fly, and affect their insulation and damages reproductive system.
  2. It interrupts the food chain which may cause extinction of species.

Question 1.(2008)

State any two sources of water pollution.
Answer:
Two sources of water pollution are :

(a) Industrial waste
(b) Sewage.

Question 2.(2008)

State the causes and consequences of ‘eutrophication’.
Answer:
Causes of eutrophication are :

(a) Increase in chemical nutrients in an ecosystem.
(b) Organic matter in sewage poured into water bodies.

Question 3.(2008)

What is meant by the term ‘offshore drilling’. State the main environmental effects of offshore drilling.
Answer:
Offshore drilling : Involves exploring for oil and gas beneath the ocean floor. Steps involved are location of wells, exploring wells to find out if there is oil below and if oil and gas ‘production well’ is drilled and an ‘oil rig’ is built to replace the exploratory drilling rig.
Environmental effects : It affects the health and reproduction of marine animals. It interrupts the food chain, which may cause extinction of species.

Question 4.(2008)

Explain why oil spills have an adverse effect on marine life.
Answer:
Oil is lighter and insoluble in water and oil layer floats on the surface of water and prevents oxygen transfer from atmosphere.
Oil leakage and petroleum products into sea water due to accidents of ships and oil tankers or leakage of pipe lines and storage tanks. They occur when oil is being produced from offshore well and may happen due to transportation by pipes and tanks, oil refineries, petrochemical plants etc.
Damage caused by oil spills :

  1. Fish, birds, reptiles and amphibians living in cannot breathe and die. The oil penetrates the birds feathers and they cannot Tly, and affect their insulation and damages reproductive system.
  2. It interrupts the food chain which may cause extinction of species.

Question 1.(2009)

Explain any two environmental impacts of an ‘oil spill’.
Answer:
See Question 2, 2007.

Question 1.(2010)

Explain the methods of controlling water pollution.
Answer:
Methods of controlling water pollution.

  1. Control of water pollution can be done by properly handling of sewage waste.
  2. Use drilling fluids which are biodegradable and have low aquatic toxicty.
  3. Develop better pollution control measures which include removal of oil, dispersing oil, removing of oil clumps.
  4. Oil and grease is removed from industrial waste by oil-water separator.
  5. Acid and alkalies are neutralized.
  6. Organic materials in waste water are removed by distillation adsorption.
  7. Biodegradable organics are removed by (a) Activated sludge process (an aerobic biochemical process) (b) Biological trickling filter process.

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