Question

Consider $35 \, g$ of oxygen at room temperature. Calculate the heat that needs to be supplied to raise it's temperature by $80 \, ^\circ C$ at constant volume. (molecular weight of oxygen is $32$ and $ \, R=8.3 \, J \, mol^{- 1}K^{- 1}$ )

• A. $1.52 \, kJ$
• B. $3.23 \, kJ$
• C. $1.81 \, kJ$
• D. $1.62 \, kJ$

Answer 1

Answer: (C)

Here mass of oxygen $\left(m\right)=35 \, g$
molar mass of O2 $\left(M\right)=32 \, g \, \left(m o l\right)^{- 1}$
rise in temperature, $\Delta T=80℃$
$\therefore number \, of \, moles \, n=\frac{m}{M}=\frac{35}{32}=1.09 \, mol$
As oxygen is a diatomic gas, then molar specific heat at constant volume is $C_{V}=\frac{5}{2}R$
and amount of heat supplied to gas
$\Delta Q=nC_{V}\Delta T=1.09\times \frac{5}{2}R\times 80=1.09\times \frac{5}{2}\times 8.3\times 80$
$=1809.4 \, J=1.8094 \, kJ=1.81 \, kJ$