For which of the following parameters the structural isomers $\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}$ and $\mathrm{CH}_{3} \mathrm{OCH}_{3}$ would be expected to have the same values? (Assume ideal behaviour)

(B) Gaseous densities at the same temperature and pressure

(D) Vapour pressure at the same temperature

JEE Main · 2004 · 24 Apr 2004 · Offline · States of Matter

For which of the following parameters the structural isomers

C_{2} H_{5} OH

and

CH_{3} OCH_{3}

would be expected to have the same values?
(Assume ideal behaviour)

(A)Heat of vaporization
(B)Gaseous densities at the same temperature and pressure✓ Correct
(C)Boiling points
(D)Vapour pressure at the same temperature

Answer: (B)

Solution

These two are structural isomers sharing the formula

C X_{2} H X_{6} O

and so the same molar mass. For an ideal gas the density is

ρ = \frac{P M}{R T}

, so at equal temperature and pressure two gases of equal molar mass must have equal densities. Their unlike intermolecular forces, with ethanol hydrogen bonding and dimethyl ether not, make their boiling points, vapour pressures and heats of vaporisation differ, but gaseous density is the property they hold in common.

JEE Main · 2004 · 24 Apr 2004 · Offline · Single correct option

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JEE Main · 2004 · 24 Apr 2004 · Offline · States of Matter

Solution

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