Question

If an ideal gas occupies 27.5 ml at 760 torr and 23 °C then, what volume would the same gas occupy at standard conditions?

Answer 1

The volume of the gas at STP is 25.4 mL

When you examine the question, you see that the pressure does not change. Standard pressure is 760 Torr. The only things that change are the volume and the temperature.

This is an example of Charles' Law.

`V_1/T_1 = V_2/T_2`

`V_1` = 27.5 mL; `T_1` = (23 + 273.15) K = 296 K
`V_2` = ?; `T_2` = (0 + 273.15) K = 273.15 K

`V_2 = V_1× T_2/T_1` = 27.5 mL ×`(273.15" K")/(296" K")` = 25.4 mL

This makes sense. The absolute temperature decreased by about 8 %, so the volume decreased by about 8 % (2 mL).