A quantity of gas is collected in a gradutated tube over the mercury. The volume of the gas at `20^(@)C` is `50.0 mL` and the level of the mercury in the tube is `100 mm` above the outside mercury level. The barometer reads `750 mm`. Volume at `STP` is

Options

A. `39.8 mL`
B. `40 mL`
C. `42 mL`
D. `60 mL`

Explanation

Effective pressure `=750-100=650` torr
Use `(P_(1)V_(1))/(T_(1))=(P_(2)V_(2))/(T_(2))`