Verified Solution • 2025–26 Session moderate

QJEEM19Cha469: JEE Main 2019 Chemistry - Class 12 JEEM19Cha469 Solution: Liquid 'M' and liquid 'N' form an ideal solution. The vapour…

Liquid 'M' and liquid 'N' form an ideal solution. The vapour pressures of pure liquids 'M' and 'N' are 450 and 700 mmHg, respectively, at the same temperature. Then correct statement is:
(xM = Mole fraction of 'M' in solution ;
xN = Mole fraction of 'N' in solution ;
yM = Mole fraction of 'M' in vapour phase ;
yN = Mole fraction of 'N' in vapour phase)

Multiple Choice Options

  • A xMxN<yNyN{{{x_M}} \over {{x_N}}} < {{{y_N}} \over {{y_N}}}
  • B (xM – yM) < (xN – yN)
  • C xMxN=yNyN{{{x_M}} \over {{x_N}}} = {{{y_N}} \over {{y_N}}}
  • D xMxN>yMyN{{{x_M}} \over {{x_N}}} > {{{y_M}} \over {{y_N}}}

Step-by-Step Verified Solution

PM0P_M^0 = 450 mmHg and PN0P_N^0 = 700 mmHg

∴\therefore PM0P_M^0 < PN0P_N^0

Also we know,

PMP_M = PM0P_M^0 XMX_M = YMY_M PTP_T

⇒\Rightarrow PM0P_M^0 = YMXM(PT){{{Y_M}} \over {{X_M}}}\left( {{P_T}} \right)

PNP_N = PN0P_N^0 XNX_N = YNY_N PTP_T

⇒\Rightarrow PN0P_N^0 = YNXN(PT){{{Y_N}} \over {{X_N}}}\left( {{P_T}} \right)

As, PM0P_M^0 < PN0P_N^0

⇒\Rightarrow YMXM(PT){{{Y_M}} \over {{X_M}}}\left( {{P_T}} \right) < YNXN(PT){{{Y_N}} \over {{X_N}}}\left( {{P_T}} \right)

⇒\Rightarrow YMXM{{{Y_M}} \over {{X_M}}} < YNXN{{{Y_N}} \over {{X_N}}}

⇒\Rightarrow YMYN{{{Y_M}} \over {{Y_N}}} < XMXN{{{X_M}} \over {{X_N}}}

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