Solutions — DPP 1

20 NEET questions from Solutions, with answers and explanations. Attempt it as a timed test to get scoring, accuracy breakdown and mistake tracking.

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1
The molarity of 900 g of water is;
  1. A 50 M
  2. B 55.5 M
  3. C 5 M
  4. D 9 M
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Correct answer: B

2
36 g water and 828 g ethyl alcohol forms an ideal solution. The mole fraction of water in it is:
  1. A 1.0
  2. B 0.7
  3. C 0.4
  4. D 0.1
Show answer & explanation

Correct answer: D

Number of moles of C$_{2}$H$_{5}$OH(n$_{1}$)= $\frac{828}{46}$ = 18
Number of moles of H₂O(n$_{2}$) = $\frac{36}{18}$ = 2
x$_\mathrm{H₂O}$ = $\frac{\mathrm{n}_{2}}{\mathrm{n}_{2}+\mathrm{n}_{1}}=\frac{2}{2+18}$ = 2 0.1
3
A solution is obtained by dissolving 0.2 moles of urea in a litre of water. Another solution is obtained by dissolving 0.4 moles of cane-sugar in a litre of water at the same temperature. The lowering of vapour pressure to the first solution is:
  1. A same as that of the second solution.
  2. B half to that of the second solution.
  3. C double to that of the second solution
  4. D None of these
Show answer

Correct answer: B

4
Which of the following solutions have more relative lowering in vapour pressure at a certain temperature?
  1. A 90 grams of glucose in 900 grams of $\mathrm{H}_{2} \mathrm{O}$.
  2. B 34.2 grams of sucrose in 450 grams of $\mathrm{H}_{2} \mathrm{O}$.
  3. C 20 grams of urea in 900 grams of $\mathrm{H}_{2} \mathrm{O}$.
  4. D 45 grams of glucose in 900 grams of $\mathrm{H}_{2} \mathrm{O}$.
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Correct answer: A

5
If two liquids A and B form minimum boiling azeotrope at some specific composition then $\_\_\_\_$ .
  1. A A-B interactions are stronger than those between A-A or $\mathrm { B } - \mathrm { B }$.
  2. B Vapour pressure of solution increases because more number of molecules of liquids A and B can escape from the solution.
  3. C Vapour pressure of solution decreases because less number of molecules of only one of the liquids escape from the solution.
  4. D A-B interactions are weaker than those between A-A or $\mathrm { B } - \mathrm { B }$.
Show answer

Correct answer: D

6
The molarity of pure water is:
  1. A 55.6
  2. B 5.56
  3. C 100
  4. D 18
Show answer & explanation

Correct answer: A

Molarity = $\frac{\text { No. of moles of solute }}{\text { Volume of solution in } L}$
Let water = 1L = 1000 mL
d$_\mathrm{H₂O}$ = 1 g/mL
∴ Mass of water = 1000 g
n$_{H₂O}$ = $\frac{\mathrm{w}}{\mathrm{M}_{\mathrm{H}_{2} \mathrm{O}}}=\frac{1000}{18}$ = 55.55 moles
Thus, molarity =$\frac{55.55 \mathrm{~mol}}{\mathrm{lL}}$ = 55.5 M
7
When 10g of a non-volatile solute is dissolved in 100g of benzene, it raises boiling point by 1°C then molecular mass of the solute is (K$_{b}$ for benzene = 2.53 kg mol$^{–1}$):
  1. A 223 g
  2. B 233 g
  3. C 243 g
  4. D 253 g
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Correct answer: D

8
The Van't Hoff factor for $0.01 \mathrm {~M } \mathrm {~Na } _ { 2 } \mathrm { SO } _ { 4 }$ solution is 1.32 . The degree of dissociation is:
  1. A $13 \%$
  2. B $16 \%$
  3. C $20 \%$
  4. D $18 \%$
Show answer

Correct answer: B

9
The freezing point of $11 \%$ aqueous solution of calcium nitrate will be:
  1. A $0 ^ { \circ } \mathrm { C }$
  2. B above $0 ^ { \circ } \mathrm { C }$
  3. C $1 ^ { \circ } \mathrm { C }$
  4. D below $0 ^ { \circ } \mathrm { C }$
Show answer

Correct answer: D

10
0.2 molal acid HX is $20 \%$ ionised in solution. $\mathrm { K } _ { \mathrm { f } } = 1.86 \mathrm {~K} \mathrm {~m} ^ { - 1 }$. The freezing point of the solution is
  1. A $- 0.45 ^ { \circ } \mathrm { C }$
  2. B $- 0.90 ^ { \circ } \mathrm { C }$
  3. C $- 0.31 ^ { \circ } \mathrm { C }$
  4. D $- 0.53 ^ { \circ } \mathrm { C }$
Show answer

Correct answer: A

11
Dissolving 120 g of urea (mol. wt. 60) in 1000 g of water gave a solution of density 1.15 g/mL. The molarity of the solution is:
  1. A 1.78 M
  2. B 2.00 M
  3. C 2.05 M
  4. D 2.22 M
Show answer & explanation

Correct answer: C

Total mass of solution $=1000+120=1120 \mathrm{~g}$
Total volume of solution in $(\mathrm{L})=\frac{\text { mass }}{\text { density }}=\frac{1120}{1.15 \times 10^{3}}$
M = $\frac{w}{M} \times \frac{1}{V(L)}$
$=\frac{120}{60} \times \frac{1.15 \times 10^{3}}{1120}$
= 2.05 M
12
The aqueous solution of 0.004 M Na₂SO₄ and 0.01 M glucose are isotonic. Degree of dissociation of Na₂SO₄ is:
  1. A 75%
  2. B 50%
  3. C 25%
  4. D 85%
Show answer & explanation

Correct answer: A

For two solutions to be isotonic;
$\pi_{\mathrm{Na}_{2} \mathrm{SO}_{4}}=\pi_{\text {glucose }}$
π = iCRT
$\mathrm{iC}_{\mathrm{Na}_{2} \mathrm{SO}_{4}}=\mathrm{iC}_{\text {glucose }}$
i × 0.004 = 1 × 0.01
i = 2.5
Na₂SO₄ → 2Na + SO$_{4}$$^{2–}$
The number of ions (n) = 3.
The degree of dissociation (α) = $\frac{i - 1}{n - 1}$
α = $\frac{2.5 - 1}{3 - 1}$= 0.75 or 75%.
13
The ratio of value of colligative property for equimolar Hg$_{2}$Cl₂ solution to that for sugar solution is nearly:
  1. A 4
  2. B 1
  3. C 8
  4. D 3
Show answer

Correct answer: D

14
Which of the following is a colligative property?
  1. A Boiling point
  2. B Freezing point
  3. C Osmotic pressure
  4. D Vapour pressure
Show answer

Correct answer: C

15
Two liquids A and B have $\mathrm { P } _ { \mathrm { A } } ^ { 0 } : \mathrm { P } _ { \mathrm { B } } ^ { 0 } = 1 : 3$ at a certain temperature. If the mole fraction ratio of $\mathrm { X } _ { \mathrm { A } } : \mathrm { X } _ { \mathrm { B } } = 1 : 3$, the mole fraction of A in vapour at equilibrium with the solution at a given temperature is:
  1. A 0.1
  2. B 0.2
  3. C 0.5
  4. D 1.0
Show answer

Correct answer: A

16
Vapour pressure of chloroform $\left( \mathrm { CHCl } _ { 3 } \right)$ and dichloromethane $\left( \mathrm { CH } _ { 2 } \mathrm { Cl } _ { 2 } \right)$ at $25 ^ { \circ } \mathrm { C }$ are 200 mmHg and 41.5 mmHg respectively. Vapour pressure of the solution obtained by mixing 25.5 g of $\mathrm { CHCl } _ { 3 }$ and 40 g of $\mathrm { CH } _ { 2 } \mathrm { Cl } _ { 2 }$ at the same temperature will be: (Molecular mass of $\mathrm { CHCl } _ { 3 } = 119.5 \mathrm { u }$ and molecular mass of $\mathrm { CH } _ { 2 } \mathrm { Cl } _ { 2 } = 85 \mathrm { u }$ )
  1. A 173.9 mmHg
  2. B 615.0 mmHg
  3. C 347.9 mmHg
  4. D 90.63 mmHg
Show answer

Correct answer: C

17
At a certain temperature, the vapour pressure of water is 90 mm. At the same temperature the vapour pressure of a solution containing a non-volatile solute is 81mm. The relative lowering of vapour pressure is:
  1. A 9
  2. B 0.9
  3. C 10
  4. D 0.1
Show answer

Correct answer: D

18
For a binary ideal liquid solution, the total pressure of the solution is given as:
  1. A $\mathrm{p}_{\text {total }}=\mathrm{p}_{\mathrm{A}}^{\circ}+\left(\mathrm{p}_{\mathrm{A}}^{\circ}+\mathrm{p}_{\mathrm{B}}^{\circ}\right) \mathrm{X}_{\mathrm{B}}$
  2. B $\mathrm{p}_{\text {total }}=\mathrm{p}_{\mathrm{B}}^{\circ}+\left(\mathrm{p}_{\mathrm{A}}^{\circ}-\mathrm{p}_{\mathrm{B}}^{\circ}\right) \mathrm{X}_{\mathrm{A}}$
  3. C $\mathrm{p}_{\text {total }}=\mathrm{p}_\mathrm{B}^{\circ}+\left(\mathrm{p}_\mathrm{B}^{\circ}-\mathrm{p}_\mathrm{A}^{\circ}\right) \mathrm{X}_\mathrm{A}$
  4. D $\mathrm{p}_{\text {total }}=\mathrm{p}_\mathrm{B}^{\circ}+\left(\mathrm{p}_\mathrm{B}^{\circ}-\mathrm{p}_\mathrm{A}^{\circ}\right) \mathrm{X}_\mathrm{B}$
Show answer & explanation

Correct answer: B

For a binary ideal liquid solution
$\mathrm{p}_{\text {total }}=\mathrm{x}_{\mathrm{A}} \mathrm{p}_{\mathrm{A}}^{\circ}+\mathrm{x}_{\mathrm{B}} \mathrm{p}_{\mathrm{B}}^{\circ}$ ........(i)
and x$_\mathrm{A}$ + x$_\mathrm{B}$ = 1
X$_\mathrm{B}$ = (1 – x$_\mathrm{A}$)
putting the value of x$_\mathrm{B}$ in equation (i)
$\begin{aligned} \mathrm{p}_{\text {Total }} & =x_{A} \mathrm{p}_{A}^{\circ}+\left(1-x_\mathrm{A}\right) \mathrm{p}_{B}^{\circ}=x_\mathrm{A} \mathrm{p}_{A}^{\circ}+\mathrm{p}_\mathrm{B}^{\circ}-x_\mathrm{A} \mathrm{p}_\mathrm{B}^{\circ} \\ \therefore \mathrm{p}_{\text {Total }} & =\mathrm{p}_\mathrm{B}^{\circ}+x_\mathrm{A}\left(\mathrm{p}_\mathrm{A}^{\circ}-\mathrm{p}_\mathrm{B}^{\circ}\right)\end{aligned}$
19
The rise in the boiling point of a solution containing 1.8g of glucose in 100g of solvent is 0.1°C. The molal elevation constant of the liquid is:
  1. A 0.01°C/m
  2. B 0.1°C/m
  3. C 1°C/m
  4. D 10°C/m
Show answer

Correct answer: D

20
Two liquids P and Q forms an ideal solution at 300 K , the vapour pressure of a solution of 1 mole of P and x mole of Q is 550 mm . If the vapour pressure of pure P and pure Q are 400 mm and 600 mm respectively then x is
  1. A 4
  2. B 2
  3. C 3
  4. D $1 / 3$
Show answer

Correct answer: C

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