Molality

Q. Find the molarity of a solution made by mixing equal volumes of 30% by weight of $H_{2}S{O}_4$ (density = 1.218 g/mL) and 70% by weight of $H_{2}S{O}_4$ (density = 1.610 g/mL) solutions.

1. 1.48 M
2. 7.61 M
3. 5.83 M
4. 9.25 M

Q. Urea solution has a molarity of $4.0{\text{mol L}}^{-1}$ and molality $4.0{\text{mol kg}}^{-1}{H}_{2}O$. Thus, the density $\left({\text{g mL}}^{-1}\right)$ of the solution is (Report the answer upto two decimals)

Q. A crystalline hydrated salt on being rendered anhydrous loses 45.6% of its weight.
The percentage composition of the anhydrous salt is:
$Al=10.5\%,K=15.1\%,S=24.8\%$ and oxygen $=49.6\%$
[Molar mass of $Al=27,K=39,S=32$].

What is the empirical formula of the salt?

1. $K_{2}Al{S}_2{O}_7$
2. $K_{2}A{l}_2{S}_2{O}_7$
3. $KAl{S}_2{O}_8$
4. $K_{3}Al{S}_2{O}_{12}$

Q. Consider a hypothetical case where a compound “A” is dissolved in water in equimolar ratio and formed a solution of average molar mass 100 g/mol. If same compound “A” formed 18.2% (w/v) solution with another solvent X then molarity of solution (A with X) would be equal to:

1. 0.001 M
2. 1 M
3. 0.01 M
4. 0.1 M

Q.

What are Molarity and molality represented by respectively?

1. m, M

2. M, m

3. Mo, mol

4. ar, al

Q. Calculate the molality of an aqueous glucose solution in which mole fraction of glucose is 0.25.

1. 20.64 m
2. 13..88 m
3. 18.26 m
4. 18.52 m

Q.

The following table gives the solubility at different temperatures Answer the question based on this.

Temperature in Kelvin

Substance dissolved	283	293	313	333	353
KNO3	21	32	62	106	167
NaCl	36	36	36	36	37
KCl	35	35	40	46	54
NH4Cl	24	37	41	55	66

Find the solubility of each salt at 293 K.

Q.

Percent by mass of a solute (molar mass = 28 g) in its aqueous solution is 28. Calculate the mole fraction (X) and molality (m) of the solute in the solution.

1. X = 0.2, m = 10

2. X = 0.2, m = $\frac{125}{9}$

3. X = 0.8, m = $\frac{125}{9}$

4. X = 0.8, m = 10

Q. The mole fraction of methanol in water is $0.12$. Calculate its molality.

1. $12.50\text{m}$
2. $7.50\text{m}$
3. $18.50\text{m}$
4. $3.25\text{m}$

Q. Calculate the molality of a 1.5 M aqueous salt solution in a solvent X, if the mole fraction of the salt in the solution is 0.25.
(Molar mass of solvent = 40 g/mol)

1. $18.52m$
2. $12.85m$
3. $8.33m$
4. $15.24m$

Q. Calculate the molality of 58.5 g of NaCl (Molar mass of NaCl= 58.5 $gmo{l}^{-1})$ dissolved in 500 g of water.

1. 1 m
2. 2 m
3. 0.5 m
4. 1.5 m

Q. What is molality of 30% (w/w) $H_2{O}_2$ aqueous solution?

1. 8.82 m
2. 12.60 m
3. 15.60 m
4. 10.67 m

Q. Calculate the molality of a 20% $CaC{O}_3$ solution (by mass). The density of the solution is 1.2 g/mL.

1. 1.25 m
2. 2.50 m
3. 2.08 m
4. 1.52 m

Q. The molarity of an aqueous solution of glycol is 10 M. The density of the solution is 1.16 g/mL. Find the mole fraction of glycol.

1. 0.5
2. 0.25
3. 0.75
4. 0.9

Q.

What is the molality of a solution having 14.2 gm of $N{a}_{2}S{O}_4$ dissolved in 1 liter solution?

1. 14.2

2. 1.42

3. 1

4. cannot be determined

Q. Find the molality of a solution made by mixing equal volumes of 60% (w/w) $H_{2}S{O}_4$ (density = 1.84 g/mL) and 40% (w/w) of $H_{2}S{O}_4$ (density = 1.52 g/mL) solutions.

1. 10.6 m
2. 12.5 m
3. 19.2 m
4. 15.7 m

Q. Calculate the molality of a $1\text{L}$ solution of 80% $H_{2}S{O}_4$ $\text{(}w/V)$, given that the density of the solution is $1.80{\text{gmL}}^{-1}$.

1. 8.16 m
2. 8.6 m
3. 1.02 m
4. 10.8 m

Q.

Identify the value of $\mathrm{X}$, if $\mathrm{X}$ molal solution of a compound in benzene has mole fraction of solute equal to $0.2$

Q. Calculate the molality of a $1L$ solution of $93\%H_{2}S{O}_4$ (w/V) . The density of the solution is $1.84gm{L}^{-1}$

1. $18.428m$
2. $10.428m$
3. $20.428m$
4. $9.428m$

Q. An aqueous solution ethanol has density $1.025gm{L}^{-1}$ and $2M$. What is the molality of this solution?

1. $1.79m$
2. $2.143m$
3. $1.951m$
4. None of these

Q. A 5 M aqueous solution of ethanol has a density of 1.025 g/mL. Find its molality

1. 5.12 m
2. 6.29 m
3. 6.69 m
4. 4.85 m

Q.

What is the mole fraction of the solute in a 1.00 m aqueous solution?

1. 1.770

2. 0.0354

3. 0.0177

4. 0.177

Q. 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. 1.78 M
2. 2.00 M
3. 2.05 M
4. 2.22 M

Q. The density of 3M solution of $N{a}_2{S}_2{O}_3$ is $1.25$ g mL${}^{-1}$. Calculate the $\%$ by weight of $N{a}_2{S}_2{O}_3$ and molality of $N{a}^{+}$ ion

1. 62.08 $\%$, 7.73 M
2. 37.92 $\%$, 7.73 M
3. 42.73 $\%$, 3.86 M
4. 58.58 $\%$, 3.86 M

Q.

Percent by mass of a solute (molar mass = 28 g) in its aqueous solution is 28. Calculate the mole fraction (X) and molality (m) of the solute in the solution.

1. X = 0.2, m = 10

2. X = 0.2, m = $\frac{125}{9}$

3. X = 0.8, m = $\frac{125}{9}$

4. X = 0.8, m = 10

Q. Molarity of $H_{2}S{O}_4$ is 18M. Its density is 1.8 g/ml. Hence molality is

1. 36
2. 200
3. 500
4. 18

Q. Find the molarity and molality of a 15% (w/w) $H_{2}S{O}_4$ solution.
(Density of the solution is 1.10 g/mL)

1. 1.53 M, 1.64 m
2. 1.68 M, 1.68 m
3. 1.80 M 1.68 m
4. 1.68 M 1.80 m

Q. The strength of a ${10}^{-2}\text{M}N{a}_{2}C{O}_3$ solution in terms of its molality will be: $(\text{density of solution}=1.10{\text{g mL}}^{-1}$, $\text{molecular weight of}N{a}_{2}C{O}_3=106{\text{g mol}}^{-1})$

1. $9.00\times {10}^{-3}$
2. $1.50\times {10}^{-2}$
3. $5.10\times {10}^{-3}$
4. $11.2\times {10}^{-3}$

Q. Molality (in $m$) of a solution in which $36g$ glucose is dissolved in $500g$ water is.

1. 0.8
2. 0.4
3. 0.2
4. 0.36

Q. If the density of a 3 M thiosulphate $\left(N{a}_2{S}_2{O}_3\right)$ solution is 1.2 g/mL, then the molality of the solution is:

1. 4.13 m
2. 2.57 m
3. 3.85 m
4. 5.46 m