The vapors of $1 \mathrm{~g}$ of an element occupy $2.5625 \mathrm{~L}$ exerting a pressure of $0.5…

The vapors of $1 \mathrm{~g}$ of an element occupy $2.5625 \mathrm{~L}$ exerting a pressure of $0.5 \mathrm{~atm}$ at $1000 \mathrm{~K}$. What is the molar mass (in $\mathrm{g} \mathrm{mol}^{-1}$ ) of the element? (Assume vapors follow ideal gas equation Given $\mathrm{R}=0.082 \mathrm{~L} \mathrm{~atm} \mathrm{~mol}^{-1} \mathrm{~K}^{-1}$ )
  1. $64$
  2. $16$
  3. $32$
  4. $128$

Solution

$\mathrm{PV}=\mathrm{nRT}=\frac{\mathrm{m}}{\mathrm{M}} \mathrm{RT} \Rightarrow \mathrm{M}=\frac{\mathrm{mRT}}{\mathrm{PV}}$ $=\frac{(1)(0.082)(1000)}{(0.5)(2.5625)}=64 \mathrm{~g} \mathrm{~mol}^{-1}$.

Asked in: AP EAMCET 2023 (18 May Shift 1)

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