Question

lain your order.List the following aqueous solutions in order of increasing boiling point: 0.12 m C6H12O6, 0.05 m LiBr, and 0.05 m Zn(NO3)2. Explain your order.

Answer 1

Answer: The order of increasing boiling points follows:

$\text{LiBr }$

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:  0.12 m $C_6H_{12}O_6$

Value of i = 1   (for non-electrolytes)

So, molal concentration will be = $(0.12)\times 1=0.12m$

• Option 2:  0.02 m LiBr

Value of i = 2

So, molal concentration will be = $(0.02)\times 2=0.04m$

• Option 3:  0.05 m $Zn(NO_3)_2$

Value of i = 3

So, molal concentration will be = $(0.05)\times 3=0.15m$

As, the molal concentration of $Zn(NO_3)_2$ is the highest, so its boiling point will be the highest.

Hence, the order of increasing boiling points follows:

$\text{LiBr }$