JEE MAIN - Physics (2019 - 12th April Evening Slot - No. 10)
A diatomic gas with rigid molecules does 10 J of work when expanded at constant pressure. What would be
the heat energy absorbed by the gas, in this process ?
35 J
30 J
25 J
40 J
Explanation
At constant pressure,
W = P$$\Delta $$V = nR$$\Delta $$T
At constant pressure, heat supplied
Q = nCp$$\Delta $$T
$${W \over Q} = {R \over {{C_p}}}$$
For diatomic gas, Cp = $${7 \over 2}R$$
$$ \therefore $$ $${{10} \over Q} = {R \over {{7 \over 2}R}}$$
$$ \Rightarrow $$ Q = 10 $$ \times $$ $${7 \over 2}$$ = 35 J
W = P$$\Delta $$V = nR$$\Delta $$T
At constant pressure, heat supplied
Q = nCp$$\Delta $$T
$${W \over Q} = {R \over {{C_p}}}$$
For diatomic gas, Cp = $${7 \over 2}R$$
$$ \therefore $$ $${{10} \over Q} = {R \over {{7 \over 2}R}}$$
$$ \Rightarrow $$ Q = 10 $$ \times $$ $${7 \over 2}$$ = 35 J
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