Dissolution of Salts in Water Class-8th Goyal Brothers ICSE Chemistry Solutions Ch-8 Unit-1

Dissolution of Salts in Water Class-8th Goyal Brothers ICSE Chemistry Solutions Ch-8(Water) Unit-1(Dissolution of Salts in Water). We Provide Step by Step Answers of Objectives, True and False, Incorrect and Correct, Definitions, Match the followings and Short/Long Question Type answers of Ch-8(Water) Unit-1(Dissolution of Salts in Water). Visit official Website  CISCE  for detail information about ICSE Board Class-8

Dissolution of Salts in Water Class-8th Goyal Brothers ICSE Chemistry Solutions Ch-8 Unit-1

Board ICSE
Class 8th
Subject Chemistry
Book Name Goyal Brothers
Chapter-8 Water
Unit-1

Dissolution of Salts in Water

Topic Solution of exercise questions
Session 2023-24

OBJECTIVE TYPE QUESTIONS

Dissolution of Salts in Water Class-8th Goyal Brothers ICSE Chemistry Solutions Ch-8 Unit-1

Que: A. Fill in the blank spaces by choosing the correct words from the given list :

List : soluble, stirred, dissolved, saturated, heating

1. When a solid disappears in water, the solid is said to be soluble.

2. A solution which cannot dissolve more of a solute at a given temperature, is called saturated solution at that temperature.

3. The solute should be stirred in the solvent for the quick formation of solution.

4. Saturated solution at a given temperature can be changed to unsaturated solution by heating it.

5. The substances which dissolve rapidly in water are called dissolved substances.

Que: B. Statements given below are incorrect. Write the correct statements :

Question: 1. The substances which dissolve very little are called soluble substances.

Answer: The substances which dissolve very little are called non soluble substances.

Question: 2. Dissolved gases in water provide softness to water.

Answer: Dissolved gases in water provide hardness to water.

Question: 3. In the summer, the fishes die in shallow ponds in the wanting of sufficient food.

Answer: In the summer, the fishes die in shallow ponds in the wanting of sufficient oxygen.

Question: 4. When concentration of salt reaches 35 g per liter of sea water, the concentration starts increasing rapidly.

Answer: When concentration of salt reaches 35 g per liter of sea water, the concentration stop increasing rapidly.

Question: 5. Starch solution and egg albumin in water are examples of solution.

Answer: Starch solution and egg albumin in water are examples of colloidal.

Que: C. Match the statements in Column A, with those in Column B :

Column A Column B
1. A liquid which dissolves other substances in it. (a) Colloid
2. A solution which can hold more of solute at a given temperature, than saturated solution. (b) Universal solvent
3. The solvent which can dissolve all kinds of matter. (c) Solvent
4. A heterogeneous mixture of insoluble particles of solute having particle size more than 10-5 cm. (d) Supersaturated
5. A heterogeneous solution in which the particle size is in between 10-7 cm to 10-5 cm. (e) Suspension

Answer :

Column A Column B
1. A liquid which dissolves other substances in it. (a) Solvent
2. A solution which can hold more of solute at a given temperature, than saturated solution. (b) Supersaturated
3. The solvent which can dissolve all kinds of matter. (c) Universal solvent
4. A heterogeneous mixture of insoluble particles of solute having particle size more than 10-5 cm. (d) Colloid
5. A heterogeneous solution in which the particle size is in between 10-7 cm to 10-5 cm. (e) Suspension

Que: Write ‘True’ or ‘False’ for the following statements :

Statements True/False
1. The process involving the dissolving of sugar in water is called dissolution. F
2. The temperature of the solvent should be low as it helps in the quick formation of solution. F
3. At a given temperature saturated solution can be changed unsaturated solution by adding more solute in it. F
4. In water certain substances dissolve rapidly, whereas certain substances very slowly. T
5. The decrease in pressure the solubility of carbon dioxide gas decreases. T

Que: E. Tick (√) the most appropriate answer :

1. A solution which cannot dissolve more of a solute at a given temperature is called :

(a) unsaturated solution

(b) saturated solution

(c) supersaturated solution

(d) any of these

Answer: option (b) saturated solution is correct.

2. The substances which dissolve rapidly in water are called :

(a) insoluble substances

(b) super soluble substances

(c) soluble substances

(d) none of these

Answer: option (b) super soluble substances is correct.

3. The size of solute particles is of order of 10-8 cm or less in

(a) solution

(b) colloid

(c) suspension

(b) none of these

Answer: option (a) solution is correct.

4. In which of the following the particles of solute can be separated by the process of filtration?

(a) solution

(b) colloid

(c) suspension

(b) all the above

Answer: option (c) suspension is correct.

5. Which of the following is translucent in nature ?

(a) solution

(b) colloid

(c) suspension

(b) none of these

Answer: option (a) solution is correct.

STUDY QUESTIONS

Dissolution of Salts in Water Class-8th Goyal Brothers ICSE Chemistry Solutions Ch-8 Unit-1

Question: 1. Define the following terms and support your answer by one example 

(a) Solute

Answer: A substance that is dissolved in a solution is called a solute. In fluid solutions, the amount of solvent present is greater than the amount of solute. One best example of solute in our day to day activity is salt and water. Salt dissolves in water and therefore, salt is the solute.

(b) Solvent

Answer: The substances present in lower concentration are solutes, while the substance present in highest abundance is the solvent. Using air as an example, oxygen and carbon dioxide gases are solutes, while nitrogen gas is the solvent.

(c) Solution

Answer: A solution consists of a solute and a solvent. The solute is the substance that is dissolved in the solvent. The amount of solute that can be dissolved in solvent is called its solubility. For example, in a saline solution, salt is the solute dissolved in water as the solvent.

Question: 2. State four conditions for the formation of solution?

Answer: The four essential conditions for the formation of a solution are –

1. Number of substancesThere should be a minimum of two substances that are readily soluble in each other. The substance in greater quantity is called a solvent and the substance in lesser quantity is called a solute.

2. MixingThe solution should be stirred continuously to ensure the proper dissolving of a solute in the solvent.

3. State of solute The solute if solid should be in the form of fine powder to dissolve it easily. If the solute is liquid then it should be properly mixed with a solvent. If the solute is gas then it should be passed through a delivery tube while keeping the container covered.

4. TemperatureThe temperature of the solvent should be higher than that of the solute as it increases the solubility of the solute in the solvent.

Question: 3. What do you understand by the following terms?

(a) Saturated solution

Answer: A saturated solution is a solution that contains the maximum amount of solute that can be dissolved under the condition at which the solution exists.

(b) Unsaturated solution

Answer: An unsaturated solution is a solution that contains less than the maximum amount of solute that is capable of being dissolved. Solution equilibrium exists when the rate of dissolution equals the rate of recrystallization.

(c) Supersaturated solution

Answer: Any solution containing more solute than required to prepare a saturated solution at any fixed temperature is called supersaturated solution. Supersaturated solution is a meta-stable state i.e. it will remain in supersaturated state so long it is left undisturbed. A slight disturbance (e.g. slight rise or fall of temperature) will turn it into a saturated solution.

Question: 4. (a) Why is temperature always mentioned with saturated solution?

Answer: The solubility of a solid in a solution increases with increasing temperature. If the temperature of a saturated solution is increased, the solution will become unsaturated. Thus, the temperature plays an important role in specifying whether a solution is saturated or not.

(b) State two ways by which a saturated solution can be changed to unsaturated solution.

Answer: There are two ways through which saturated solution can be changed to the unsaturated solution :

  • By Heating It.
  • By adding more solvent to it.

Question: 5. Why is water called ‘universal solvent’?

Answer: Water is called the “universal solvent” because it is capable of dissolving more substances than any other liquid.

Question: 6. Briefly explain the importance of dissolved gases in water.

Answer: The importance of dissolved gases can be explained by the following points –

1. Human consumption –

  • The dissolved gases in water give it a particular taste.
  • oxygen gas kills some germs that can cause diseases.

2. For the survival of aquatic organisms –

  • Dissolved gases like oxygen are necessary for the respiration of organisms living in the water.
  • Carbon dioxide gas is essential as raw material for photosynthesis.

3. For industrial use –

  • Carbon dioxide gas is dissolved in soft drinks to create a fizz.
  • In the production of chemicals like hydrochloric acid and many more.

Question: 7. By giving two characteristics define the following :

(a) Solution

Answer: Characteristics of Solutions :

  • It is a homogeneous mixture.
  • We can not the see its particles even with a microscope.
  • Particles of solutions can pass through the filter paper.
  • Particles of solutions are generally stable

(b) Colloidal solution

Answer: Characteristics of colloidal solution :

  • Colloids are heterogeneous in nature.
  • The size of particle ranges from 1 nanometer (10-9 m) 1 micrometer (10-6 m).
  • In a colloidal solution, particles can scatter light and the path of the light beam becomes visible.
  • This scattering of light by colloidal particles is known as the Tyndall effect.

(c) Suspension

Answer: Characteristics of Suspension solution:

  • It is a type of heterogeneous mixture
  • In a suspension particles of the solute do not dissolve in the solvent, they remain suspended throughout the solvent
  • The size of particles of suspension is greater than 1 nanometer (10-9 m), so it can be visible from naked eyes.
  • It shows the Tyndall effect because of their large size of particles.

Question: 8. Give at least three differences between the following :

(a) Solution and colloidal Solution

Answer:

Solution Colloidal Solution
1. The particle size is less than 10-8 cm. The particle size is in between 10-7 cm to 10-5 cm.
2. The particles are not visible under a powerful microscope. The particle are visible under a microscope.
3. The particles of a solution can be recovered by evaporation and crystallisation. The particles of a colloidal solution cannot be recovered by evaporation and crystallisation.
4. The particles of a solution do not scatter light. The particles of a colloidal solution scatter light.
5. Solutions are clear and transparent. Colloidal solutions are translucent.
6. Solutions are homogeneous. Colloidal solutions are heterogeneous in nature.

(b) Colloidal Solution and Suspension

Answer:

Colloidal Solution Suspension
1. The particle size is in between 10-7 cm to 10-5 cm. The size of the particles of solute is more than 10-5 cm.
2. The particle are visible under a microscope. The particles of suspension settle down when a suspension is allowed to stand.
3. The particles of a colloidal solution cannot be recovered by evaporation and crystallisation. The particles of suspension can easily be filtered out.
4. The particles of a colloidal solution scatter light. The particles of suspension are visible to the unaided eye.

— : end of Dissolution of Salts in Water Class-8th Goyal Brothers ICSE Chemistry Solutions Ch-8 U-1 :–

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