Water ICSE class 9

Question 1

Potassium reacts with water to produce _______ flame.

yellow

green

lilac

red

 Solution

Potassium burns in water with lilac coloured flame.

Question 2

The homogenous mixture of solute and solvent is called _______ .

salt

solution

compound

mixture

Solution

Solute and solvent together mix to form a solution.

Question 3

A desiccator is an air tight glass vessel with a suitable drying agent, _______ placed at the bottom of the vessel.

concentrated sulphuric acid

ammonium chloride

copper oxide

anhydrous calcium chloride

Solution

A desiccator is an air tight glass vessel with a suitable drying agent, anhydrous calcium chloride placed at the bottom of the vessel.

Question 4

Which of the following are hydrated salts?

Green vitriol

Gypsum

Soda ash

Both A and B

Solution

Green vitriol (FeSO₄.7H₂O) and Gypsum (CaSO₄.2H₂O) contain fixed number of water molecules as water of crystallization in loose chemical combination. Hence, they are hydrated salts.

Question 5

The crystals of sodium chloride produces crackling sound on heating, called _________ .

deliquescence

crystallisation

hydration

decrepitation

Solution

The bigger crystals of sodium chloride breaks up into smaller ones producing crackling sound called as decrepitation.

Question 6

_______ is a colourless gas which is produced by the reaction of active metal with dilute hydrochloric acid.

Nitrogen

Water gas

Hydrogen

Oxygen

Solution

Hydrogen gas produced by active metals on reaction with dilute hydrochloric acid.

Question 7

Which of the following is not applicable to solutions?

Solutions do not scatter a beam of light passing through them.

The constituents are uniformly mixed.

The particles in a solution are very small in size.

Solutions exist only in liquid state.

Solution

Solutions exist only in liquid state. Solution can exist in all the three states.

Question 8

The effect of temperature on the solubility of gas in a liquid is governed by _______ .

Henry's law

Gay Lussac's law

Boyle's law

Charles law

Solution

The Henry's law gives us the idea of effect of temperature and pressure on solubility of gas in a liquid.

Question 10

The specific latent heat of vapourization of water is _______ .

80 kcal/kg

226 cal/kg

540 cal/g

1 cal/g

Solution

The specific latent heat of vapourization of water is 540 cal/g or 2260 J/g.

Question 11

Methylated spirit is used to dissolve _______ .

phosphorus

chlorophyll

sulphur

All the above

Solution

Chlorophyll dissolves in methylated spirit.

            Question 9

A solution in which the amount of solute is relatively small as compared to the amount of solvent is called a _______ solution.

super saturated

saturated

dilute

concentrated

Solution

In a dilute solution, amount of solute is relatively small as compared to the amount of solvent in a given mass.

Question 12

The effect of temperature on the solubility of gas in a liquid is governed by __________ .

Charles law

Henry’s law

Gay Lusac’s law

Boyle’s law

Solution

The Henry’s law gives us the idea of effect of temperature and pressure on solubility of gas in a liquid.

Question 13

Methylated spirit is used as a solvent to dissolve __________ .

Chlorophyll

Phosphorus

Sulphur

All the above

Solution

Chlorophyll dissolves in methylated spirit.

Question 14

Which of the following is not a physical property of water?

Water contract when cooled upto 4^oC.

The specific heat capacity of water is 1 calorie/(gram^oC).

It is a colourless liquid.

On increasing pressure the freezing point of water increases.

Solution

On increasing pressure the freezing point of water decreases.

Question 15

In ferrous sulphate crystal (FeSO₄ .7H₂O), '7H₂O' represents the _______ .

water of crystallization           

water vapour

binding agent

reaction product

Solution

A fixed amount of water that is associated with crystals is called as water of crystallization.

Question 16

Water is a _______ .

mixture

element

compound

Solution

Water is a compound.

Question 17

The size of solute should be __________ for better solubility.

any type

Big

Huge

Small

Solution

Smaller the size of solute particle, greater is the solubility.

Question 18

The solvent used to dissolve solute phosphorus is __________ .

Alcohol

methylated spirit

Water

carbon disulphide

Solution

Phosphorus dissolves in carbon disulphide solvent.

Question 19

Metals react with water to form metal oxide and _______ .

non-metal oxide

acid

hydrogen gas

water gas

Solution

Metals react with water (cold, warm, hot and steam) to produce metal oxide and hydrogen gas.

eg:     Mg     +     H₂O     →     MgO     +     H₂ ↑

    Magnesium     Water     Magnesium  Hydrogen gas

                                          oxide

Question 20

The solid bounded by the plane surfaces directed at definite angles and having definite geometrical shapes are called

Cubes

Solid

Crystals

Amorphous solid

Solution

The solid bounded by the plane surfaces directed at definite angles and having definite geometrical shapes are called crystals.

Question 21

Efflorescent salts are:

Salts that lose water of crystallisation when exposed to air

Salts that gain water of crystallisation when exposed to air

Salts that are easily soluble in water

Both a and c

Solution

Efflorescent salts when left exposed to air lose their water of crystallisation and crumble down to powder.

Question 22

The drying agent for chlorine gas is _________ .

Calcium oxide

Zinc nitrate

Sulphuric acid

Sodium nitrate

Solution

Concentrated sulphuric acid is used as drying agent for chlorine gas.

Question 23

What is the ratio of solute and solvent in a concentrated solution?

More solute less solvent

Less solute more solvent

Equal quantities of solute and solvent

All the above

Solution

When amount of solute dissolved is relatively large as compared to the quantity of solvent, then the solution is called concentrated solution.

Question 24

Which one of the following metals does not react with water at any conditions?

Gold

Iron

Lead

Potassium

Solution

Gold does not react with water as it is present below hydrogen in the metal activity series.

The metals which are placed below the hydrogen in the metal activity series can not displace hydrogen ion.

                 Question 25

The solubility curve is a graph between solubility of a __________ in a sovent against changing __________ .

gas ; temperature

solid ; temperature

gas ; pressure

solid ; pressure

Solution

The solubility curve is a line graph, that plots changes in the solubility of a solute (solid) in a solvent against changing temperature.

Question 26

What is blue vitriol?

FeSO₄.7H₂O

FeSO₄.5H₂O

CuSO₄.7H₂O

CuSO₄.5H₂O

Solution

Blue vitriol is CuSO₄.5H₂O (hydrated copper sulphate).

Question 27

A solution in which more of the solute can be dissolved at a given temperature is known as a/an _______ solution.

Pure

Unsaturated

super saturated

Saturated

Solution

A solution in which more of the solute can be dissolved at a given temperature is known as a/an unsaturated solution.

Question 28

Which of the following absorb moisture from air:

Green vitriol

Common salt

Soda ash

Both a and b

Solution

Green vitriol and common salt increase weight when exposed to air. They absorb moisture from air.

Question 29

On heating hydrated salt of copper sulphate, it turns _________ colour.

Green

Blue

Yellow

White

Solution

Hydrated copper sulphate on heating changes its colour from blue to white.

Question 30

The solubility curve is a graph between _______ and _______ .

solubility of solid; temperature

solubility of gas; pressure

solubility of gas; temperature

solubility of solid; pressure

Solution

Solubility curve is the graph between solubility of solid and temperature.

Question 1

An acid can be prepared from water by its reaction with metallic oxide.

False

True

Solution

False. Metallic oxides react with water to form alkalis.

Question 2

When sodium is placed in water, it burns with violet flame.

False

True

Solution

False. Sodium burns in water with a golden yellow flame.

Question 3

The solid substance that can dissolve in a solvent is known as solute.

False

True

Solution

True

Question 4

Sodium oxide is soluble in water.

True

False

Solution

True

Question 5

The particles of true solution do not settle down under the influence of gravity.

True

False

Solution

True

Question 6

Hygroscopic substances are also called drying agents.

True

False

Solution

True

Question 7

At 4^oC pure water has minimum volume and maximum density.

True

False

Solution

True

                Question 8

The supersaturated solution can hold more of the solute at a room temperature than that present in a saturated solution.

False

True

Solution

True

Question 9

Solids are dried by passing them through a drying tower or a U-tube containing anhydrous sodium sulphate.

True

False

Solution

Gases are dried by passing them through a drying tower or a U-tube containing anhydrous sodium sulphate.

Question 10

Turpentine oil is as a solvent for removing paint stains.

False

True

Solution

True

Question 11

The anhydride of suplhuric acid is sulphur trioxide.

True

False

Solution

True

Question 12

Solubility increases with rise in temperature for potassium nitrate.

True

False

Solution

True

Question 13

The solubility curve is used to find the solubility of a given solute in a solvent within a range of temperature.

False

True

Solution

The solubility curve is used to find the solubility of a given solute against changing temperature

Question 14

Solubility increases with rise in temperature for potassium nitrate.

True

False

Solution

True

Question 15

Solubility curve is used to find the solubility of a given substance within a range of temperature.

False

True

Solution

True

Question 16

The solid substance which dissolves in the solvent to form a solution is called as a solute.

True

False

Solution

True

Question 17

Magnesium chloride is a deliquescent salt.

True

False

Solution

True

Question 18

A solution that cannot dissolve any more of the solute at given temperature is called as an unsaturated solution.

True

False

Solution

A solution that cannot dissolve any more of the solute at given temperature is called as a saturated solution.

Question 19

The process of inducing crystallization by adding a crystal of pure substance into its saturated solution is called water of crystallization.

True

False

Solution

The process of inducing crystallization by adding a crystal of pure substance into its saturated solution is called seeding.

Question 20

Anhydrous crystalline salt of potassium which is purple in colour is potassium manganate.

True

False

Solution

True

Question 1

(a) Define

(i) Solute

(ii) Solvent

(iii) Dispersed phase

(iv) Dispersion medium

(b) Classify solutions on the basis of solubility.

Solution

(a) (i) A solid component which dissolves in liquid (solvent) is called solute.

(ii) A liquid component which allows the solid to dissolve in it is called solvent.

(iii) In a colloidal system one substance is dispersed as very fine particles in another substance, the dispersed substance or state is called the dispersed phase.

(iv) The continuous medium, such as a gas, liquid or a solid, in which a dispesed phase is distributed is called the dispersion medium.

(b) Solution can also be classified on the basis of their solubility, i.e, depending upon the amount of solute that dissolves in a given solvent.

(i) Unsaturated solution: If more solute can be dissolved in a solvent at a particular temperature, then the solution is called unsturated solution.

(ii) Saturated solution: If no more solute can be dissolved in a solvent at a particular temperature, then the solution is called saturated solution.

(iii) Supersaturated solution: If the solution contains more of the solute, then the saturated solution at a particular temperature is called suprsaturated solution.

Select the metals which do not displace hydrogen from water:
a. Silver
b. Lead
c. Copper
d. Sodium
e. Mercury
f. Calcium
g. Gold
h. Potassium
Give reasons for your choices.

Solution

Silver, Copper, Gold, and Mercury do not displace hydrogen from water. This is because they are present below hydrogen in the metal activity series.

Efflorescent salts are:

Salts that lose water of crystallisation when exposed to air

Salts that gain water of crystallisation when exposed to air

Salts that are easily soluble in water

Both a and c

Solution

Correct Option: Salts that lose water of crystallisation when exposed to air

Explanation:

Efflorescent salts when left exposed to air lose their water of crystallisation and crumble down to powder.

Question 4

Water is a _______ of electricity because it doesnot form ions.

non-conductor

semi-conductor

good conductor

None of the above

Solution

Correct Option: non-conductor

Explanation:

Water is a non-conductor of electricity because it doesnot form ions.

Question 5

(a) Write the balanced chemical equations for the following metals with water.
(i) Sodium
(ii) Potassium
(iii) Calcium
(iv) Magnesium
(v) Iron
(b) The following questions refer to the electrolysis of acidulated water.
(i) Name the electrodes at which hydrogen and oxygen are liberated.
(ii) Give the equations for the reactions taking place at cathode and at anode.
(iii) What is the ratio by volume for hydrogen and oxygen?

Solution

Question 6

On increasing temperature the solubility of a gas in liquid _____.

Solution

decreases

Question 7

Why is ferric chloride stored in airtight bottles?

Solution

Ferric chloride is highly deliquescent in nature. When exposed to atmosphere it absorbs moisture and gets converted into its saturated solution, therefore it should be stored in airtight bottles.

Question 8

The solid substance that can dissolve in a solvent is known as solute.

False

True

Solution

Correct Option: True

Explanation:

True

Question 10

What are drying agents? Give 2 examples.

Solution

The substances which easily absorb moisture from the other substances are called drying agent.
For example: Concentrated sulphuric acid, calcium oxide.

Question 11

Why does common salt becomes wet during rainy season?

Solution

Common salt is NaCl with impurities of MgCl₂. This MgCl₂ is deliquescent, which on exposure to air absorbs moisture and gets converted to saturated solution. Thus, common salt becomes wet during rainy season. Common salt is neither hygroscopic nor deliquescent.

Question 12

How is temperature related to solubility of gas in a liquid? What is the effect of increasing and decreasing temperature on the solubility of the gas in a liquid?

Solution

The solubility of gas in a liquid is inversely proportional to temperature.
On increasing the temperature the solubility of gas in a liquid decreases.
On decreasing the temperature the solubility of gas in a liquid increases.

Question 13

What is blue vitriol?

FeSO₄.5H₂O

FeSO₄.7H₂O

CuSO₄.7H₂O

CuSO₄.5H₂O

Solution

Correct Option: CuSO₄.5H₂O

Explanation:

Blue vitriol is CuSO₄.5H₂O (hydrated copper sulphate).

Question 14

Gas ‘A’ is a colourless gas which is produced by the reaction of active metals with dilute HCl. Gas ‘B’ is produced by the action of heat on potassium chlorate. Gas ‘A’ undergoes reaction with gas ‘B’ and forms colourless liquid ‘C’.

(i) Identify A, B and C.

(ii) Give balanced chemical equation for the formation of liquid ‘C’ from ‘A’ and ‘B’.

(iii) Give two tests to identify liquid ‘C’.

(iv) Give balanced chemical equation for the reaction of ‘C’ with-

      (a) Sulphur dioxide

      (b) Sodium oxide

      (c) Ammonia

      (d) Carbon dioxide

Solution

(i)                

A – Hydrogen

B – Oxygen

C – Water

(ii) 2H₂  +  O₂  →  2H₂O

(iii) Liquid ‘C’ can be testedby the following two ways:

(a)  It turns white coloured anhydrous copper sulphate to blue.

(b)  It turns blue coloured anhydrous cobalt chlorideto pink.

(iv) (a) SO₂  +  H₂O  →  H₂SO₃

                                Sulphurous acid

      (b) Na₂O  +  H₂O  →  2NaOH

                                Sodium hydroxide

      (c) NH₃  +  H₂O  →  NH₄OH

                            Ammonium hydroxide

      (d)    CO₂  +  H₂O  →  H₂CO₃

                                   Carbonic acid

Question 15

What are the factors that determine solubility of a substance?

Solution

The solubility of a substance depends on:
(i) Temperature
(ii) Size of solute particles
(iii) Nature of solvent

Question 16

Define solubility.

Solution

The amount of solute dissolved in 100g of solvent to form saturated solution at a particular temperature is known as solubility.

Question 17

Solubility curve is used to find the solubility of a given substance within a range of temperature.

False

True

Solution

Correct Option: True

Explanation:

True

Question 18

Give two differences between deliquescent substance and hygroscopic substance.

Solution

S.No.	Deliquescent substances	Hygroscopic substances
(1)	These are solid crystalline in nature.	They may be crystalline solid or liquids.
(2)	They absorb moisture from atmosphere and dissolve in it to form saturated solution.	They absorb moisture from atmosphere and dissolve in it but do not form saturated solution.

Question 19

Name two metals which react vigorously with water.

Solution

Sodium and Potassium

Question 20

(a) How will you prepare the following from water?
(i) Water gas
(ii) Hydrogen
(iii) Acid
(iv) Alkali
(b) Why the salt content in the cooked vegetable remains the same, whether the cooked food is hot or cold?
(c) Name the following salts.
(i) A decahydrated crystalline salt.
(ii) Anhydrous crystalline salt of potassium which is purple in color.
(iii) A hydrated crystalline salt which is green in color.
(iv) A pentahydrated crystalline salt which is blue in color.
(v) Salt which is commonly called Sal ammoniac.

Solution

(b) The salt mainly used for cooking purpose is common salt (NaCl) and its solubility does not change with temperature.

(c)

(i) Washing soda Na₂CO₃.10H₂O

(ii) Potassium permanganate KMnO₄

(iii) Hydrated ferrous sulphate or green vitriol FeSO₄.7H₂O

(iv) Hydrated copper sulphate or blue vitriol. CuSO₄.5H₂O

(v) Ammonium chloride NH₄Cl