Question

Choose the aqueous solution that has the highest boiling point.These are all solutions of nonvolatile solutes and you shouldassume ideal van't Hoff factors where applicable.
a. 0.100 m NaNO3
b. 0.100m Li2SO4
c. 0.200m C3H8O3
d. 0.060m Na3PO4

Answer 1

Answer: The correct answer is Option b.

Explanation:

The expression of elevation in boiling point is given as:

$\Delta T_b=i\times k_b\times m$

where,

$\Delta T_b$ = Elevation in boiling point

i = Van't Hoff factor  

$T_b$ = change in boiling point

$k_b$ = boiling point constant

m = molality

For the given options:

Option 1:  0.100 m $NaNO_3$

Value of i = 2

So, molal concentration will be = $(0.100)\times 2=0.200m$

Option 2:  0.100 m $Li_2SO_4$

Value of i = 3

So, molal concentration will be = $(0.100)\times 3=0.300m$

Option 3:  0.200 m $C_3H_8O_3$

Value of i = 1  (for non-electrolytes)

So, molal concentration will be = $(0.200)\times 1=0.200m$

Option 4:  0.060 m $Na_3PO_4$

Value of i = 4

So, molal concentration will be = $(0.060)\times 4=0.24m$

As, the molal concentration of $Li_2SO_4$ is the highest, so its boiling point will be the highest.

Thus, the order of increasing boiling points follows:

$NaNO_3=C_3H_8O_3$

Hence, the correct answer is Option b.