In an isothermal process on an ideal gas, the pressure increases by 0.5 percent. The volume decreases by about __________ percent.

In an isothermal process as we $$PV = {\text{constant}}$$
$$ \Rightarrow $$ on applying $$\log $$ we get $$\log P + \log V = \operatorname{log\,Constant} $$      on differentiating we get $$\frac{{dP}}{P} + \frac{{dV}}{V} = 0,$$
So, $$\frac{{dV}}{V} * 100 = - \frac{{dp}}{p} * 100$$     given the pressure has a percentage increase of $$0.5$$
So, the volume will have a percentage decrease of $$0.5.$$