Question

1 g mole of an ideal gas at STP is subjected of a reversible adiabatic expression to double its volume. The change in internal energy ($\gamma$ = 1.4)

• A. 1169 J
• B. 769 J
• C. 1373 J
• D. 969 K

Answer 1

Answer: (C)

1373 J

Answer 2

: For adiabatic expansion $T _ { 1 } V _ { 1 } ^ { \gamma - 1 } = T _ { 2 } V _ { 2 } ^ { \gamma - 1 }$

$T _ { 2 } = T _ { 1 } \left( \frac { V _ { 1 } } { V _ { 2 } } \right) ^ { \gamma - 1 } = 273 \left( \frac { 1 } { 2 } \right) ^ { 1.4 - 1 } = 206$

$d U = d W = \frac { R } { \gamma - 1 } \left( T _ { 1 } - T _ { 2 } \right) = \frac { 1 \times 8.31 } { ( 1.4 - 1 ) } ( 273 - 206.89 )$ $= 1373 J$