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

Answer: Option B

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