# A gas at 34 ""^@C expressed a volume of 10*L in a piston; what is the new volume at 48 ""^@C?

Old Charles' Law holds that ${V}_{1} / {T}_{1} = {V}_{2} / {T}_{2}$, moles and pressure constant.........
Pressure is a constant here, but we know (or should know) that $1 \cdot a t m$ pressure will support a column of mercury that is $760 \cdot m m \cdot H g$ tall; this relationship is linear: 1/2 an atmosphere will support a column of mercury that is $380 \cdot m m \cdot H g$ tall. A mercury manometer is thus useful to measure laboratory pressures of confined gases.
And so ${V}_{2} = {V}_{1} / {T}_{1} \times {T}_{2} = \frac{10 \cdot L}{307 \cdot K} \times 348 \cdot K \cong 11 \cdot L$