9. Solutions

I. Choose the best answer.

1. A solution is a ____ mixture.

(a) homogeneous
(b) heterogeneous
(c) homogeneous and heterogeneous
(d) non – homogeneous.

2. The number of components in a binary solution is:

(a) 2                (b) 3
(c) 4                 (d) 5

3. Which of the following is the universal solvent?

(a) Acetone     (b) Benzene
(c) Water        (d) Alcohol.

4. A solution in which no more solute can be dissolved in a definite amount of solvent at a given temperature is called:

(a) Saturated solution
(b) Unsaturated solution
(c) Supersaturated solution
(d) Dilute solution

5. Identify the non – aqueous solution ______.

(a) sodium chloride in water
(b) glucose in water
(c) copper sulphate in water
(d) sulphur in carbon-di-sulphide.

6. When pressure is increased at a constant temperature the solubility of gases in liquid:

(a) No change              (b) increases
(c) decreases               (d) no reaction

7. The solubility of NaCl in 100 ml water is 36 g. If 25 g of salt is dissolved in 100 ml of water how much more salt is required for saturation ______.

(a) 12 g            (b) 11 g
(c) 16 g            (d) 20 g.

8. A 25% alcohol solution means:

(a) 25 ml alcohol in 100 ml of water
(b) 25 ml alcohol in 25 ml of water
(c) 25 ml alcohol in 75 ml of water
(d) 75 ml alcohol in 25 ml of water

9. Deliquescence is due to ______.

(a) Strong affinity to water
(b) Less affinity to water
(c) Strong hatred of water
(d) Inertness to water.

10. Which of the following is hygroscopic in nature?

(a) ferric chloride
(b) copper sulphate penta hydrate
(c) silica gel
(d) none of the above

II. Fill in the blanks.

1. The component present in a lesser amount, in a solution, is called Solute.

2. Example for liquid in solid type solution is Sodium chloride dissolved in water.

3. Solubility is the amount of solute dissolved in 100g of solvent.

4. Polar compounds are soluble in Polar solvents.

5. Volume percentage decreases with increases in temperature because of Expansion of liquid.

III. Match the following.

Blue vitriol

(c) CuSO4.5H2O

Gypsum

(a) CaSO4.2H2O

Deliquescence

(d) NaOH

Hygroscopic

(b) CaO

IV. True or False: (If false give the correct statement)

1. Solutions which contain three components are called binary solution.
      Answer:     False.
Correct Statement: Solutions which contain two components are called binary solution.

2. In a solution, the component which is present in a lesser amount is called solvent.
    Answer:       False.
Correct Statement:

  • In a solution, the component which is present in a larger amount is called a solvent.
  • In a solution, the component which is present in a lesser amount is called solute.

3. Sodium chloride dissolved in water forms a non-aqueous solution.
     Answer:      False.
Correct Statement: Sodium chloride dissolved in water forms an aqueous solution.

4. The molecular formula of green vitriol is MgSO4.7H2O
     Answer:      False.
Correct Statement: The molecular formula of green vitriol is FeSO4 .7H2O

5. When Silica gel is kept open, it absorbs moisture from the air, because it is hygroscopic in nature.
  Answer:         True.

V. Short Answer Questions.

1. Define the term Solution.

A solution is a homogeneous mixture of two or more substances.

2. What is mean by binary solution?

Solutions which are made of one solute and one solvent, then it is called binary solution.

3. Give an example each

  1. gas in liquid
  2. solid in liquid
  3. solid in solid
  4. gas in gas.

Answer:

  1. Carbon – di – oxide dissolved in water (Soda water).
  2. Sodium chloride dissolved in water.
  3. Copper dissolved in gold (Alloy).
  4. A mixture of Helium – Oxygen gases.

4. What is aqueous and non-aqueous solution? Give an example.

(i) Aqueous solution : The solution in which water acts as a solvent.
(ii) Non-aqueous solution : The solution in which any liquid other than water acts as a solvent.
Eg: Alcohol, benzene, CS2 acetone.

5. Define Volume percentage.

Volume percentage is defined as the percentage by volume of solute (in ml) present in the given volume of the solution.


6. The aquatic animals live more in cold region Why?

Aquatic animals live more in cold regions because the solubility of O2 in water is more at low temperature and therefore the amount of dissolved O2 is more in the water of cold regions.

7. Define Hydrated salt.

The number of water molecules found in the crystalline substance or salts is called water of crystallization. Such salts are called hydrated salts.

8. A hot saturated solution of copper sulphate forms crystals as it cools. Why?

A hot saturated solution of CuSO4 forms crystal as it cools. Because on cooling the water molecules move closer together and there is less space for the solution to hold on to as much of the dissolved solid and so it forms crystals.

9. Classify the following substances into deliquescent, hygroscopic. Conc. Sulphuric acid, Copper sulphate penta hydrate, Silica gel, Calcium chloride, and Gypsum salt.

  1. Deliquescent substances: Calcium chloride
  2. Hygroscopic substances: Conc Sulphuric acid, Copper sulphate penta hydrate, Silica gel and Gypsum salt.

VI. Long Answer Questions.

1. Write notes on
(i) saturated solution
(ii) unsaturated solution
Answer:
(i) Saturated solution : A solution in which no more solute can be dissolved in a definite amount of the solvent at a given temperature is called saturated solution.
Eg: 36 g of sodium chloride in 100 g of water at 25°C forms saturated solution.

(ii) Unsaturated solution : Unsaturated solution is one that contains less solute than that of the saturated solution at a given temperature.
Eg: 10 g or 20 g or 30 g of Sodium chloride in 100 g of water at 25°C forms an unsaturated solution.

2. Write notes on various factors affecting solubility.
Answer:
Factors affecting solubility: There are three main factors which govern the solubility of the solute. They are
(i) Nature of the solute and solvent
(ii) Temperature
(iii) Pressure

(i) Nature of the solute and solvent: The nature of the solute and solvent plays an important role insolubility. Although water dissolves an enormous variety of substances, both ionic and covalent, it does not dissolve everything. The phrase that scientists often use when predicting solubility is “like dissolves like.” This expression means that dissolving occurs when similarities exist between the solvent and the solute. For example, Common salt is a polar compound and dissolves readily in polar solvent like water.

Non – polar compounds are soluble in non-polar solvents. For example, Fat dissolved in ether. But non-polar compounds, do not dissolve in polar solvents; polar compounds do not dissolve in non-polar solvents.

(ii) Effect of Temperature
The solubility of Solids in Liquid: Generally, the solubility of a solid solute in a liquid solvent increases with increase in temperature. For example, a greater amount of sugar will dissolve in warm water than in cold water.
In the endothermic process, solubility increases with increase in temperature. In the exothermic process, solubility decreases with increase in temperature.

The solubility of Gases in liquid: Solubility of gases in liquids decreases with increase in temperature. Generally, water contains dissolved oxygen. When water is boiled, the solubility of oxygen in water decreases, so oxygen escapes in the form of bubbles. Aquatic animals live more in cold regions because more amount of dissolved oxygen is present in the water of cold regions. This shows that the solubility of oxygen in water is more at low temperatures.

(iii) Effect of Pressure: Effect of pressure is observed only in the case of solubility of a gas in a liquid. When the pressure is increased, the solubility of a gas in liquid increases.
The common examples for solubility of gases in liquids are carbonated beverages, i.e. soft drinks, household cleaners containing an aqueous solution of ammonia, formalin aqueous solution of formaldehyde, etc.

3. (a) What happens when MgSO4.7H2O is heated? Write the appropriate equation.
(b) Define solubility.
Answer:
(a) MgSO4.7H2O has a water of crystallization is 7. When magnesium sulphate heptahydrate crystals are gently heated, it loses seven water molecules and becomes anhydrous magnesium sulphate.


(b) Solubility: It is defined as the number of grams of a solute that can be dissolved in 100 g of a solvent to form its saturated solution at a given temperature and pressure.

4. In what way, hygroscopic substances differ from deliquescent substances.
Answer:
Difference between hygroscopic and deliquescent substances is in the extent to which each material can absorb moisture. This is because both of these terms are very much related to each other and they refer to the property of observing and the retention of moisture from the air. However, they differ in the extent of absorption of moisture where hygroscopic materials absorb moisture but not to the extent the original substance dissolves in it, which is the case with deliquescence. Therefore deliquescence can be regarded as an extreme condition of hygroscopic activity.

Difference between hygroscopic substances and deliquescence

Hygroscopic Substances

Deliquescence Substances

When exposed to the atmosphere at ordinary temperature, they absorb moisture and do not dissolve.

When exposed to the atmospheric air at ordinary temperature, they absorb moisture and dissolve.

Hygroscopic substances do not change their physical state on exposure to air.

Deliquescent substances change its physical state on exposure to air.

Hygroscopic substances may be amorphous solids or liquids.

Deliquescent substances are crystalline solids.

5. A solution is prepared by dissolving 45 g of sugar in 180 g of water. Calculate the mass percentage of solute.
Answer:
Mass of sugar (solute) = 45 g
Mass of water (solvent) = 180 g.


6.    3.5 litres of ethanol is present in 15 litres of an aqueous solution of ethanol. Calculate volume per cent of the ethanol solution.
Answer:

VII. HOT Questions.

1. Vinu dissolves 50 g of sugar in 250 ml of hot water, Sarath dissolves 50 g of same sugar in 250 ml of cold water. Who will get faster dissolution of sugar? and Why?
Answer:
Vinu will get faster dissolution of sugar. Because Vinu dissolves 50 g of sugar in 250 ml of hot water, whereas Sarath dissolves 50 g of sugar in 250 ml of cold water. Solubility of a solid in liquid increases with increase in temperature.

2. ‘A’ is a blue coloured crystalline salt. On heating, it loses a blue colour and to give ‘B’. When water is added, ‘B’ gives back to ‘A’. Identify A and B, write the equation.
Answer:

  • Blue coloured crystalline salt is copper sulphate pentahydrate (A)
  • On heating Copper sulphate pentahydrate it loses blue colour and to give anhydrous copper sulphate (B).
  • When water is added to the anhydrous copper sulphate (B) gives back to copper sulphate pentahydrate (A).

3. Will the cool drinks give more fizz at top of the hills or at the foot? Explain.

Carbonated cool drinks give more fizz at the foot hill because solubility of gases in liquid decrease with increase in temperature. At higher altitudes, the temperature is low and the dissolved CO2 will not escape as fizz, whereas at the foot hill it does.