The vapour pressure of water at $20^{\circ} \mathrm{C}$ is 17.5 mm Hg. If 18 g of glucose $\left(\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}\right)$ is added to 178.2 g of water at $20^{\circ} \mathrm{C}$, the vapour pressure of the resulting solution will be

JEE Main · 2008 · 27 Apr 2008 · Offline · Solutions

The vapour pressure of water at

2 0^{\circ} C

is 17.5 mm Hg. If 18 g of glucose

(C_{6} H_{12} O_{6})

is added to 178.2 g of water at

2 0^{\circ} C

, the vapour pressure of the resulting solution will be

(A)17.675 mm Hg
(B)15.750 mm Hg
(C)16.500 mm Hg
(D)17.325 mm Hg✓ Correct

Answer: (D)

Solution

By Raoult's law the fractional lowering of vapour pressure equals the mole fraction of the solute. There are

\frac{18}{180} = 0.1 mol

of glucose and

\frac{178.2}{18} = 9.9 mol

of water, so the solute mole fraction is

\frac{0.1}{10.0} = 0.01

. Then

\frac{17.5 - P _{s}}{17.5} = 0.01

gives a lowering of

0.175 mm Hg

, so the solution's vapour pressure is

17.5 - 0.175 = 17.325 mm Hg

JEE Main · 2008 · 27 Apr 2008 · Offline · Single correct option

Practise more: all JEE Main PYQs on Solutions →

More JEE Main questions on Solutions

Elements P and Q form two types of non-volatile, non-ionizable compounds PQ and $PQ_{2}$ . When 1 g of PQ is dissolved in 50 g of solvent 'A', $Δ T_{b}$ was 1.176 K while when 1 g of $PQ_{2}$ is dissolved in 50 g of solvent 'A', …
JEE Main 2026View solution →
Consider a solution of $CO_{2} (g)$ dissolved in water in a closed container.

Which one of the following plots correctly represents variation of log (partial pressure of CO2 in vapour phase above water) [y-axis] with log (mole fraction of $CO_{2}$ …
JEE Main 2026View solution →
Given below are two statements:

Statement I: The Henry's law constant $K_{H}$ is constant with respect to variations in solution's concentration over the range for which the solutions is ideally dilute.
Statement II : $K_{H}$ does not diff …
JEE Main 2026View solution →
The osmotic pressure of a living cell is 12 atm at 300 K. The strength of sodium chloride solution that is isotonic with the living cell at this temperature is $____$ $g L^{- 1}$ . (Nearest integer)

Given: …
JEE Main 2026View solution →
A substance 'X' (1.5 g) dissolved in 150 g of a solvent 'Y' (molar mass $= 300 g mol^{- 1}$ ) led to an elevation of the boiling point by 0.5 K. The relative lowering in the vapour pressure of the solvent 'Y' is $____$ $\times 1 0^{- 2}$ . (Nearest integer)
[Giv …
JEE Main 2026View solution →
Which one of the following graphs accurately represents the plot of partial pressure of $CS_{2}$ vs its mole fraction in a mixture of acetone and $CS_{2}$ at constant temperature ?
JEE Main 2026View solution →