Question

An ideal gas expands against a constant external pressure of $2$ atmosphere from $20$ litre to $40$ litre and absorbs $10KJ$ of heat from surrounding. What is the change in internal energy of the system?

• A. $4052J$
• B. $5948J$
• C. $14052J$
• D. $9940J$

Answer 1

Answer: (C)

$14052J$

$\Delta H=\Delta U+W$

expansion $P_1{V}_1=P_2{V}_2$

$P_1=P_2=2atm=2\times 1.0132\times {10}^5$ Pa

$V_1=2ol=20\times {10}^{-3}{m}^3$

$V_2=4ol=40\times {10}^{-3}{m}^3$

$P_1{V}_1=P_2{V}_2=-2\times 1.0132\times 20\times {10}^2$

$=-4.0528\times {10}^3$

$\Delta U=10KJ+4.0528KJ$

$\Delta U=14052J$