Chapter 4.3 – Solution | Chapter Solution Class 9

Santra Physical Science Class 9

Publisher	: Santra publication pvt. ltd.
Book Name	: Madhyamik Physical Science And Environment
Class	: 9 (Madhyamik)
Subject	: Physical Science
Chapter Name	: Solution

Table of Contents

Multiple Choice Questions (MCQ)

[Each of Mark-1]

Question 1

A solution is

solvent dissolved in solute
a heterogeneous mixture
a homogeneous mixture
only a liquid in liquid

Answer

a homogeneous mixture

Explanation

A solution is a homogeneous mixture of solute and solvent, which can be any combination of phases, not limited to liquids.

Question 2

Depending on “which phase dissolves in which phase”, how many types of solutions do we consider ?

Answer

Question 3

A true solution has the feature

particle size less than 1 nm
separation by filtration
solute particles are large groups of particles
separation by a semipermeable membrane

Answer

particle size less than 1 nm

Explanation

A true solution has the feature of having solute particles with a size less than 1 nm and cannot be separated by filtration or a semipermeable membrane.

Question 4

A colloidal solution is associated with the feature

solute particles are large groups of insoluble particles
particle size is 1 to 100 nm
separation by filtration
none of these

Answer

particle size is 1 to 100 nm

Explanation

A colloidal solution is associated with the feature of having solute particles with a size between 1 and 100 nanometers and cannot be separated by filtration.

Question 5

A suspension is associated with the features

solutes are atoms or ions
particle size is 1 to 100 nm
particle size is less than 100 nm
separation by filtration

Answer

particle size is less than 100 nm

Explanation

A suspension is associated with the feature of having particles with a size greater than 100 nanometers and can be separated by filtration. Suspensions may contain solutes that are atoms, ions, or larger particles.

Question 6

Mist or fog are examples of a colloid where A is dispersed in B. A and B are

A	B
(a) gas	liquid
(b) liquid	gas
(c) liquid	liquid
(d) solid	liquid

Answer

(a) gas-liquid.

Explanation

Mist or fog are examples of a colloid where liquid droplets (A) are dispersed in a gas (B). Therefore, the correct answer is (a) gas-liquid.

Question 7

Which of the following is not a colloidal solution?

icecream
milk
smoke
NaCl in water

Answer

NaCl in water

Explanation

NaCl in water is not a colloidal solution, as it forms an ionic solution due to the ions dissociating into smaller ions in water.

Icecream and milk are colloidal solutions of solid and liquid particles in liquid.
Smoke is a colloidal solution of solid particles in gas.

Question 8

Which of the following is not a technical name of colloids?

foam
sol
gel
olium

Answer

Olium

Explanation

“Olium” is not a technical name of colloids.

Foam, sol, and gel are technical names of colloids.
Olium is not a recognized term for colloids.

Question 9

An alloy is a colloid having dispersed and medium as

liquid in solid
solid in liquid
liquid in liquid
solid in solid

Answer

solid in solid.

Explanation

An alloy is a colloid having a solid dispersed phase and a solid medium. Therefore, the correct answer is (d) solid in solid.

Question 10

Soap or detergent is an example of

emulsifier
sol
aerosol
solid foam

Answer

emulsifier

Explanation

Soap or detergent is an example of an emulsifier, which is a substance that can help mix two immiscible substances, such as oil and water.

Answer in one word or in one sentence

[Each of Mark-1]

Question

Define a solution.
Define colloid with respect to size of particles.
Define suspension.
Define solubility.
Give an example where solubility decreases with increasing T.
What would happen to solubility of gas in water if P is increased?
Give an example of a solution of solid in liquid.
Which one depends on temperature: molarity or molality?
Define molarity.
Define molality.
What is mole fraction?
Give an example of solid in gas colloid.
Give an example of solid in solid colloid.
By which method components of colloids can be separated?
Give an example of an emulsifier.

Answer

Homogeneous mixture of solute and solvent.
A colloid has particles in the range of 1-100 nanometers in size.
Suspension is a Heterogeneous mixture with large particles (>100 nm) that settle over time.
The maximum amount of solute that can dissolve in a given amount of solvent at a specific temperature and pressure.
The solubility of gases in water decreases with increasing temperature (e.g. carbonated water).
The solubility of gas in water increases with increasing pressure.
Saltwater, where salt is the solute and water is the solvent.
Molarity depends on temperature as volume changes with temperature.
The number of moles of solute dissolved in 1 litre of solution is called molarity.
The number of moles of solute per kilogram of solvent.
The mole fraction is the ratio of the moles of one component to the total moles in the solution.
Smoke is a solid in gas colloid.
Brass (alloy) is a solid in solid colloid.
Components of colloids can be separated by filtration, centrifugation, or dialysis.
Soap is an example of an emulsifier.

Short answer type questions

[Each of Mark-2]

Question 1

Differentiate between saturated and unsaturated solution.

Answer

Saturated solutions contain the maximum amount of solute that can be dissolved at a specific temperature, while unsaturated solutions can still dissolve more solute.
Additional solute added to a saturated solution forms a precipitate, while in an unsaturated solution, it dissolves.
A saturated solution is in dynamic equilibrium with the undissolved solute, while an unsaturated solution is not in equilibrium.

Question 2

What is a supersaturated solution?

Answer

A supersaturated solution is a solution that has dissolved more solute than is normally possible at a given temperature and pressure, often achieved by dissolving the solute at a high temperature and then cooling it slowly.

Question 3

How one can make a unsaturated solution from a saturated solution?

Answer

To make an unsaturated solution from a saturated solution, one can add more solvent to the solution, which will dilute the solute and reduce its concentration below the saturation point.

Question 4

How would you identify a solution as saturated or unsaturated solution?

Answer

To identify a solution as saturated or unsaturated, add more solute to the solution. If the solute dissolves completely, the original solution was unsaturated, but if it forms a precipitate, it was saturated.

Question 5

Milk and fog: what category do they belong to ?

Answer

Milk is a colloid of liquid droplets (fat) dispersed in a liquid medium (water), while fog is a colloid of liquid droplets (water) dispersed in a gas medium (air).

Question 6

Differentiate between true solution and colloid.

Answer

The size of the particles in a true solution is less than 1 nanometer, while in a colloid, it is between 1-100 nanometers.
True solutions are homogeneous mixtures with no visible particles, while colloids are heterogeneous mixtures with visible particles that scatter light.
True solutions do not exhibit the Tyndall effect, while colloids do exhibit the Tyndall effect.

Question 7

At 30°C, 45 g of KNO₃ dissolved in 100 g of water gives a saturated solution. What is the solubility of KNO₃ in water at that temperature? [Ans. 45]

Answer

Mass of solute = 45 g

Mass of solvent = 100 g

The solubility of KNO₃ in water at 30°C can be calculated as follows:

Solubility = ${45\over 100}×100$ = 45

Therefore, the solubility of KNO₃ in water at 30°C is 45.

Question 8

40 g NaOH is dissolved in 5 L water solution. Express the concentration in g/L. [Ans. 8 g/L]

Answer

Amount of NaOH = 40 g

Volume of solution = 5 L

Concentration = $Amount\ of\ NaOH \over Volume\ of\ solution$

Substituting the given values, we get:

Concentration = $40\over 5$ = 8 g/L

Therefore, the concentration of NaOH in the solution is 8 g/L.

Question 9

12.5 g NaCl is dissolved in water and the volume is made exactly 250 cc. What is the weight percentage of the solution? [Ans. 5%]

Answer

Mass of solute = 12.5 g

Volume of solution = 250 cc

Step 1 : Calculation of mass of solution

mass of solution = 250 cc × 1 g/cc = 250 g

Step 2 : Calculation of weight percentage

Weight percentage = $mass\ of\ solute\over mass\ of\ solution$ × 100%

= $12.5\over 250$ × 100% = 5%

Therefore, the weight percentage of the solution is 5%.

Question 10

How does pressure affect the solubility of liquid in liquid and gas in liquid solution?

Answer

For liquid in liquid solutions, pressure has little effect on solubility because liquids are relatively incompressible.

For gas in liquid solutions, an increase in pressure increases solubility, while a decrease in pressure decreases solubility.

Long answer type questions

[Each of Mark-3]

Question 1

Define solute, solvent and solution. Give example.

Answer

Solute: A solute is a substance that is dissolved in a solvent to form a solution. It is typically a solid, liquid, or gas that dissolves in another substance. Example: In saltwater, salt is the solute that dissolves in water.
Solvent: A solvent is a substance that dissolves the solute to form a solution. It is typically a liquid, but can also be a gas or a solid in some cases. Example: In saltwater, water is the solvent that dissolves the salt.
Solution: A solution is a homogeneous mixture of two or more substances, typically consisting of a solute dissolved in a solvent. Example: Saltwater is an example of a solution, where salt (solute) is dissolved in water (solvent) to form a homogeneous mixture.

Question 2

What is a saturated solution? How it can be made to be a super-saturated solution?

Answer

A saturated solution is a solution that contains the maximum amount of solute that is capable of being dissolved in a solvent at a given temperature.

To make a saturated solution into a supersaturated solution, you can:

Heat the solution. This will increase the solubility of the solute, allowing you to dissolve more of it in the solution.
Slowly cool the solution. As the solution cools, the solubility of the solute will decrease, but the solute will not immediately crystallize.

Question 3

What is solubility? Explain the effect of temperature on solubility.

Answer

Solubility: Solubility is the maximum amount of solute that can dissolve in a given amount of solvent at a specific temperature and pressure.

Effect of Temperature on Solubility:

The effect of temperature on solubility depends on the solute and solvent involved. Generally, for solid solutes dissolved in a liquid solvent, solubility increases with an increase in temperature. This is because an increase in temperature increases the kinetic energy of the solvent molecules, making them more likely to collide with and break apart the solute molecules, allowing more of it to dissolve.

Question 4

Give an example of each of the following cases (on increasing temperature) (i) solubility increases, (ii) solubility decreases, (iii) solubility remains almost unchanged.

Answer

(i) Solubility increases with an increase in temperature:

Sugar in water: The solubility of sugar in water increases with increasing temperature. This is because an increase in temperature increases the kinetic energy of the water molecules, which makes it easier for them to break apart and dissolve the sugar molecules.
Sodium chloride in water: The solubility of sodium chloride in water also increases with increasing temperature. This is because an increase in temperature increases the solubility of ionic compounds in water.

(ii) Solubility decreases with an increase in temperature:

Oxygen in water: The solubility of oxygen in water decreases with increasing temperature. This is because an increase in temperature decreases the attractive forces between the oxygen and water molecules, making it more difficult for the oxygen molecules to dissolve in the water.
Carbon dioxide in water: The solubility of carbon dioxide in water also decreases with increasing temperature. This is why carbonated beverages lose their fizziness when they are warmed up.

(iii) Solubility remains almost unchanged with an increase in temperature:

Calcium sulfate in water: The solubility of calcium sulfate in water remains almost unchanged with an increase in temperature. This is because calcium sulfate is a sparingly soluble salt, and the solubility product is not significantly affected by changes in temperature.

Question 5

What is colloid? What is aerosol ? How do they pollute air?

Answer

A colloid is a mixture in which one substance is dispersed evenly throughout another substance, forming a homogeneous solution.

An aerosol is a type of colloid in which solid or liquid particles are suspended in a gas, typically air.

Pollution of air due to colloid and aerosol

Colloids and aerosols are released into the air through natural or human-made sources
They contribute to air pollution and can have harmful effects on human health
The small size of the particles allows them to enter the lungs and bloodstream, causing respiratory problems and worsening existing health conditions.

Question 6

What is soda water? Why do bubbles occur when you unscrew the cap? What happens if you make the bottle hot?

Answer

Soda water is carbonated water that has been infused with carbon dioxide gas under pressure.

When you unscrew the cap of soda water, the pressure inside the bottle is released, causing the carbon dioxide gas dissolved in the water to come out of solution and form bubbles.

If you heat up a bottle of soda water, the solubility of carbon dioxide in water decreases, causing the carbon dioxide gas to come out of solution and form bubbles. This can cause the bottle to burst or foam over if the pressure inside the bottle exceeds its capacity.

Question 7

Which of the following solutions are true solution and which are colloidal : milk, sugar syrup, blood, solution of methanol, smoke, ice cream, paint, soap, NaCl in water.

Answer

True Solution: Solution of methanol, NaCl in water, sugar syrup

Colloidal Solution: Milk, blood, smoke, ice cream, paint, soap

Note: NaCl in water can also form a colloidal solution under certain conditions, but typically it is considered a true solution at low concentrations.

Question 8

At 35°C, in 75 g of saturated solution of a salt, there are 25 g of the solute. Determine the solubility of the salt. [Ans. 50]

Answer

Mass of solute = 25 g

Mass of solvent = 75 – 25 = 50 g

There appears to be an error in the provided answer. Using the given information, the solubility of the salt can be calculated as follows:

Solubility = $mass\ of\ solute \over mass\ of\ solvent$

Solubility = ${25 \over 50}×100$

Solubility = 50

Therefore, the solubility of the salt at 35°C is 50.

Question 9

Mention two units for expressing the concentration of a solution. How can you convert from one unit to the other?

Answer

Two units for expressing the concentration of a solution are molarity (M) and molality (m).

Molarity (M) = $moles\ of\ solute\over volume\ of\ solution\ (in\ litres)$

Molality (m) = $moles\ of\ solute \over mass\ of\ solvent\ (in\ kilograms)$

To convert from molarity to molality or vice versa, we need to know the density of the solvent. We can use the following formula:

Molarity = $molality × molecular\ weight\ of\ solute \over\ density\ of\ solvent × 1000$

Molality = $Molarity × density\ of\ solvent × 1000 \over molecular\ weight\ of\ solute$

By using the density and molecular weight values, we can convert between molarity and molality.

Question 10

250 mL of a NaCl solution contains 29 g of NaCl dissolved in water. Express the concentration in different units. [Ans. 116 g/L, 13.1% ]

Answer

Concentration (g/L) = $Mass\ of\ solute\ (g) \over Volume\ of\ solution\ (L)$
Percent concentration (%) = $Mass\ of\ solute\ (g) \over Mass\ of\ solution\ (g)$ × 100%

Step 1: Given the information