Solutions Test 6

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Solutions Test 6

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Weekly Quiz Competition

Question 1
1 / -0

The osmotic pressure of a 0.010 M MgSO₄ solution at 500 K is 0.82 atm. Calculate , the van’t Hoff factor, for this MgSO₄ solution.

A
3

B
2

C
1

D
4

Solution
Question 2
1 / -0

Benzoic acid dissolved in benzene will show a molecular weight of

A
366g

B
122g

C
61g

D
244g

Solution

In benzene, benzoic acid exist as dimer. So the molecular weight of benzoic acid gets doubled.
(C₆H₅COOH)₂=2×122=244 units .
Question 3
1 / -0

Molar mass that is either lower or higher than expected or normal molar mass is called as

A
Abnormal molar mass

B
Standard molar mass

C
Mass defect

D
Normal molar mass

Solution

The correct answer is option A
In chemistry, when the molar masses are calculated and if they are higher or lower than the expected value are known as abnormal molar masses. These are calculated using the colligative properties. Colligative properties include; elevation of boiling point, lowering of vapor pressure, freezing point depression, and ease of osmotic pressure. The name in itself has abnormal in it which suggests the abnormality of how the molar masses are being calculated, using the Van’t Hoff factor.
Question 4
1 / -0

0.01 M solution of common salt (NaCl) and (CH₃COOH ) is taken. If their osmotic pressures are p₁and p₂ resp., what will be the correct statement correlating their osmotic pressures?

A
p₁ = p₂

B
p₁ > p₂

C
p₁< p₂

D
p₁ = p₂=O

Solution

The correct answer is Option B.
The osmotic pressure of the NaCl solution is more due to the Van't Hoff factor of NaCl.
Van't Hoff factor of NaCl is 2.
The Van't Hoff factor of acetic acid is between 1 and 2.
Hence P₁7P₂
Question 5
1 / -0

If α is the degree of dissociation of Na₂SO₄, the vant Hoff’s factor (i) used for calculating the molecular mass is

A
1 + 2α

B
1 - α

C
1 + α

D
1 - 2α

Solution
Question 6
1 / -0

Lowering of vapour pressure is highest for

A
0.1M BaCl₂

B
0.1M MgSOl₄

C
0.1M Urea

D
0.1M Ethanol

Solution
Question 7
1 / -0

Increasing the temperature of solution of a weak electrolyte will cause

A
No change in van’t Hoff factor

B
Decrease in van’t Hoff factor

C
Depends on nature of solute.

D
Increase in van’t Hoff factor

Solution

The correct answer is option D
Increase in the temperature of solution of a weak electrolyte will result in an increase in degree of dissociation causing increase in
van’t Hoff factor.
Question 8
1 / -0

What is the freezing point of 0.1 m glucose solution in water? For water Kf is 1.86 K kg/mol?

A
1 K

B
6.55 °C

C
-0. 186 °C

D
0 K

Solution

The correct answer is option C
Since glucose is a nonelectrolyte the van’t Hoff factor i = 1
ΔT_f= iK_fm
=1.86 x 0.1
=0.186
0^oC – T_f =0.186
T_f= - 0.186^oC
Question 9
1 / -0

van’t Hoff factor is denoted by letter

A
i

B
I

C
v

D
z

Solution

The correct answer is option A
The Van't Hoff Factor is denoted by the letter 'i'. Where abnormal molar mass is determined experimentally and colligative properties are obtained by keeping in mind that solute (non-volatile) is neither associated or dissociated.
The Van’t Hoff Factor is denoted by the letter ‘i’.
Van’t Hoff defined this factor as follows:

Where abnormal molar mass is determined experimentally and colligative properties are obtained by keeping in mind that solute (non-volatile) is neither associated or dissociated.
In the case of dissociation i < 1.
And in the case of association i > .
Thus, equations for colligative properties can be modified as follows after inclusion of Van’t Hoff factors.
Relative lowering of vapour pressure of solvent
(p⁰₁ - p₁)/p⁰₁ = i.(n₂/n₁)
Elevation of boiling point,

Depression of Freezing point,

Osmotic pressure of solutions,
Question 10
1 / -0

The ratio of osmotic pressure of a 1:1 electrolyte AB to that of a non electrolyte solute of same concentration is

A
2:1

B
1:1

C
0.5:1

D
0.1:3

Solution

The correct answer is Option A.
The Van't Hoff factor of 1:1 electrolyte is 2 since it dissociates into two ions. van’t Hoff factor of a non electrolyte is 1 since it does not dissociate into ions. Hence ratio of osmotic pressure will be 2:1