Answer
6.08 mL
Work Step by Step
$P_{1}=0.80\,atm= 0.80\,atm\times\frac{760\,mmHg}{1\,atm}$$=608\,mmHg$
$V_{1}=25\,mL$
$P_{2}=2500\,mmHg$
Recall that $P_{1}V_{1}=P_{2}V_{2}$ (if $n$ and $T$ are constant)
$\implies V_{2}=\frac{P_{1}V_{1}}{P_{2}}=\frac{608\,mmHg\times 25\,mL}{2500\,mmHg}=6.08\,mL$
