Question

An open end manometer consists of $0.75$ moles of $X_g$ taken in a container of volume $24.63$ lit at $300K$. The level of mercury in the open tube is found to be 14 cm lower. The height difference when manometer is heated to $450K$ will be:

• A. $14.5cm$
• B. $21cm$
• C. $13cm$
• D. $17cm$

Answer 1

Answer: (A)

$14.5cm$

$pv=nRT$

$p=\frac{nRT}{v}=\frac{0.75\times 0.0821\times 300}{24.63}=0.75atm$

$1atm=760mmHg$

$0.75atm=(760\times 0.75)mmHg=570mmHg=57cmHg$

Again at $T=450K$,

$P=\frac{nRT}{V}=\frac{0.75\times 0.0821\times 450}{24.63}=855mmHg=85.5cmHg$

$Difference=(85.5-57)cm=28.5cm$

Initially, mercury is $14cm$ lower.

$\therefore$ The highest difference $=28.5cm-14.0cm=14.5cm$