For reference, the ideal gas law is [tex]PV=nRT[/tex].
[tex]\frac{P_0V_0}{PV} =\frac{n_0RT_0}{nRT}[/tex]
(Variables with a subscript of 0 are the values at 45°C and variables without a subscript are the values at 70°C.)
Assuming constant pressure:
[tex]V=\frac{V_0T_0}{T} =\frac{(8.5 \text{ L})(45 \text{{\textdegree}C})}{70 \text{{\textdegree}C}} =5.464 \text{ L}[/tex]
The number with the least significant figures is 70 (1 s.f.), so with correct significant figures, the volume would be 5 L.
