Chemistry Water Test

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Chemistry Water Test - 1

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Question 1
1 / -0

Emulsions are a colloidal mixture of two immiscible liquids. For example, milk is an emulsion of fat in water. The components of this emulsion can be separated by

A
separating funnel

B
centrifugation

C
filtration

D
distillation

Solution

Even though it is a mixture of immiscible liquids, the components will not separate out into layers because the dispersed phase, being particles of colloidal size will remain suspended.
However, centrifugation will cause the less dense component (in this case fat) to float on top.
Question 2
1 / -0

The property of the particles of a true solution that makes it a homogeneous mixture is

A
the small size of the solute particles

B
the large intermolecular spaces between the solvent molecules

C
the larger bulk of the solvent

D
the lesser forces of attraction between the solute and the solvent molecules

Solution

The particles of the solute are small in size and have a small mass. Hence, the force of gravity acting on them is small and they do not settle down under the effect of their own weight, but remain in motion and maintain the uniformity of the composition by moving from their higher concentration to their lower concentration.
As a result, a solution is a homogeneous mixture.
Question 3
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The method of crystallisation is based on the

A
difference between the boiling points of the components of the mixture

B
difference between the wetting properties of the components of the mixture

C
difference between the solubilities of the solute in the same solvent at different temperatures

D
difference between the melting points of the components

Solution

Pure crystals of a salt are extracted by cooling its supersaturated solution. First, a supersaturated solution is prepared by heating a substance as the solubility increases on heating. When this solution is cooled slowly, the pure crystals separate out as the solubility decreases on cooling.
Question 4
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If the solute in a solution can no more be dissolved at a given temperature, the solution is called

A
saturated

B
unsaturated

C
super saturated

D
crystallised

Solution

A saturated solution is a solution that contains the maximum amount of solute that is capable of being dissolved. At 20°C, the maximum amount of NaCl that will dissolve in 100 g of water is 36.0 g. If any more NaCl is added past that point, it will not dissolve because the solution is saturated.
Question 5
1 / -0

In which of the following colloids, are the dispersed phase and the dispersing medium both in liquid states?

A
Milk

B
Fog

C
Mud

D
Cheese

Solution

Colloidal solutions are heterogeneous mixtures having two separate phases called dispersed phase and dispersing medium. The solute like component which has been dispersed or distributed throughout in a solvent like medium is called the dispersed phase, while the solvent like medium in which the dispersed phase has been distributed is called the dispersion medium. Milk is a colloid in which both dispersed phase and dispersing medium are in liquid states.
Question 6
1 / -0

Which of the following mixtures is also a solution?

A
Mixture of milk and water

B
Mixture of sand and water

C
Mixture of salt and water

D
Mixture of cement and water

Solution

A solution is defined as a homogeneous mixture of two or more chemically non–reacting substances whose composition can be varied within limits. If a mixture is to be called a solution, it must satisfy the following two conditions:
(i) The components of a mixture should be non–reacting.
(ii) Mixture should be homogeneous.
Question 7
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Which of the following compounds is used for water softening?

A
Ca₃(PO₄)₂

B
Na₃PO₄

C
Na₆P₆O₁₈

D
Na₂HPO₄

Solution

Polyphosphates, such as sodium hexametaphosphate, combine with cations (Ca²⁺ or Mg²⁺) to form soluble complexes.

2Ca²⁺ + Na₂[Na₄(PO₃)₆] 4Na⁺ + Na₂[Ca₂(PO₃)₆]
Question 8
1 / -0

When a zeolite, which is hydrated sodium aluminium silicate, is treated with hard water, the sodium ions are exchanged with

A
Ca²⁺ and Mg²⁺

B
OH^-

C
SO₃^2-

D
H⁺

Solution

Na₂Al₂Si₂O₈.xH₂O is written as Na₂Z, Na⁺ ions exchange Ca²⁺ and Mg²⁺ ions in hard water.

Na₂Z + Mg²⁺ 2Na⁺ + MgZ

Na₂Z + Ca²⁺ 2Na⁺ + CaZ
Question 9
1 / -0

Temporary and permanent hardness of water can be removed by:

A
Boiling

B
Distillation

C
Filtration

D
Decantation

E
-

Solution

Distillation is a process of separating the component substances from a liquid mixture by selective evaporation and condensation. Distillation removes temporary and permanent hardness of water.
Question 10
1 / -0

Temporary hardness of water can be removed using:

A
Calgon process

B
Fischer-Tropsch process

C
Clark's method

D
Ion exchange method

Solution

Temporary hardness of water is removed in Clark's process by adding lime.
Ca(HCO₃)₂ + Ca(OH)₂ 2CaCO₃ ↓ + 2H₂O
Temporary hardness of water is due to the presence of bicarbonates of magnesium and calcium.
They react with calcium hydroxide to form carbonates of magnesium and calcium.
Thus, the temporary hardness of water is removed.
Question 11
1 / -0

The cation exchange resins consist of giant organic molecules containing the ________ group.

A
-Cl

B
-COOH

C
-OH

D
-NH₃

Solution

Giant organic molecules having acidic or basic groups are known as ion-exchange resins. The cation exchange resins consist of giant organic molecules containing the -COOH group. Acid resins exchange their H+ ions with other cations such as Ca²⁺, Mg²⁺, etc. present in hard water.
Question 12
1 / -0

Which of the following cannot be used for water softening?

A
Ca(OH)₂

B
Na₂CO₃.10H₂O

C
(NaPO₃)₆

D
MgCl₂

Solution

Magnesium chloride cannot be used for water softening as it results in water hardening.
Calcium and magnesium dissolved in water are the two most common minerals that make water "hard." The degree of hardness becomes greater as the calcium and magnesium content increases and is related to the concentration of multivalent cations dissolved in the water.
Question 13
1 / -0

The removal of both temporary and permanent hardness of water can be effected by

A
boiler scale

B
boiling and Clark's process

C
ion-exchange method

D
additives like Na₂CO₃/calgon

E
calcium/magnesium stearate

Solution

Ion exchange is a method widely used in the household (laundry detergents and water filters) to produce soft water. It is used for the removal of both temporary and permanent hardness of water. It is also used to remove other substances from the water in processes such as dealkalisation, deionisation, denitrification and disinfection.
Question 14
1 / -0

Which of the following is a heterogeneous mixture?

A
Brass

B
Atmospheric air

C
Vinegar

D
Blood

E
#

Solution

Blood is a heterogeneous mixture of several cells and proteins in a watery solvent. These cells and proteins can be separated out by centrifugation.
Question 15
1 / -0

Which of the following substances is an example of a colloidal solution formed from liquid as a dispersed phase and from solid as a dispersing medium?

A
Face cream

B
Butter

C
Shaving cream

D
Milky glass

E
#

Solution

Colloidal solution of a liquid dispersed in solid is called gel. The dispersion medium is solid and the disperse phase is liquid. Examples of gel include cheese, butter, jellies.

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Chemistry Water Test - 1

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Question 1

separating funnel

centrifugation

filtration

distillation

Solution

Question 2

the small size of the solute particles

the large intermolecular spaces between the solvent molecules

the larger bulk of the solvent

the lesser forces of attraction between the solute and the solvent molecules

Solution

Question 3

difference between the boiling points of the components of the mixture

difference between the wetting properties of the components of the mixture

difference between the solubilities of the solute in the same solvent at different temperatures

difference between the melting points of the components

Solution

Question 4

saturated

unsaturated

super saturated

crystallised

Solution

Question 5

Milk

Fog

Mud

Cheese

Solution

Question 6

Mixture of milk and water

Mixture of sand and water

Mixture of salt and water

Mixture of cement and water

Solution

Question 7

Ca3(PO4)2

Na3PO4

Na6P6O18

Na2HPO4

Solution

Question 8

Ca2+ and Mg2+

OH-

SO32-

H+

Solution

Question 9

Boiling

Distillation

Filtration

Decantation

-

Solution

Question 10

Calgon process

Fischer-Tropsch process

Clark's method

Ion exchange method

Solution

Question 11

-Cl

-COOH

-OH

-NH3

Solution

Question 12

Ca(OH)2

Na2CO3.10H2O

(NaPO3)6

MgCl2

Ca₃(PO₄)₂

Na₃PO₄

Na₆P₆O₁₈

Na₂HPO₄

Ca²⁺ and Mg²⁺

OH^-

SO₃^2-

H⁺

-NH₃

Ca(OH)₂

Na₂CO₃.10H₂O

(NaPO₃)₆

MgCl₂

additives like Na₂CO₃/calgon