When an ideal gas in a cylinder was compressed isothermally by a piston, the work done on the gas was found to be $1.5\times {10}^{4}Joules$.  During this process about.
 

In isothermal compression there is always an increases of heat. Which must flown out of the gas.

$\begin{array}{l}\mathrm{\Delta }Q=\mathrm{\Delta }U+\mathrm{\Delta }W=\mathrm{\Delta }Q=\mathrm{\Delta }W[\because \mathrm{\Delta }U=0]\\ \mathrm{\Delta }Q=-1.5\times {10}^{4}J=\frac{-1.5\times {10}^4}{4.18}\mathrm{cal}\\ \mathrm{\Delta }Q=-3.6\times {10}^3\mathrm{cal}\end{array}$