Question

The vapour pressure of a solution $(b)$ as a function of temperature $(a)$ is plotted as a graph for two solutions of same molar concentration along with water as shown below. $A, B$ and $C$ are respectively

• A. $H _{2} NCONH _{2}, H _{2} O , NaCl$
• B. $H _{2} O , H _{2} NCONH _{2}, NaCl$
• C. $NaCl , H _{2} O , H _{2} NCONH _{2}$
• D. $NaCl , H _{2} NCONH _{2}, H _{2} O$

Answer 1

Answer: (A)

The vapour pressure of a solution $(b)$ as a function of tcmpcraturc $(a)$ is plotted as a graph for two solutions of same molar concentration along with water.

Here, $A$ is $NH _{2}- \overset{\underset{||}{O}}{C} - NH _{2}$

$B$ is $H _{2} O$

$C$ is $NaCl$.



When number of moles of solute decreases, then vapour pressure of solution increases.

So, $H _{2} NCONH _{2}$ does not associate or dissociate.

$H _{2} O$ forms hydrogen bonding and associates vapour pressure increases. It dissociates to very small extent.

$ NaCl$ dissociates, (as it is a strong electrolyte there number of moles increases therefore vapour pressure decreases.