One mole of a monatomic ideal gas undergoes an adiabatic expansion in which its volume becomes eight times its initial value. If the initial temperature of the gas is 100 universal gas constant 8.0, the decrease in its internal energy, in , is__________.

Answer

900

Explanation

`T V^(gamma - 1) = T_f (8V)^(gamma - 1)`
` rArr T_f = (T)/( (8)^(5/3 - 1) ) = T/4`
` Delta U = n C_v Delta T = n (3R)/(2) (T/4 - T)`
` = n(3R)/(2) ( - (3T)/(4) )`
` = - 3/2 xx 8.0 xx 3/4 xx 100 = - 900 J`
Decrease in internal energy is 900 J.