Question

A 250 mL sample of gas is collected over water at 35°C and at a total pressure of 735 mm Hg. If the vapor pressure of water at 35°C is 42.2 torr, what is the volume of the gas sample at standard pressure?

Answer 1

The volume of the gas sample at standard pressure is 819.5ml

Step-by-step explanation:

Solution Given:

let volume be V and temperature be T and pressure be P.

`V_1=250ml`

`V_2=?`

`P_(total)=735 mmhg`

1 torr= 1 mmhg

42.2 torr=42.2 mmhg

so,

`P_(water)=42.2mmhg`

`T_1=35°C=35+273=308 K`

Now

firstly we need to find the pressure due to gas along by subtracting the vapor pressure of water.

`P_(gas)=P_(total)-P_(water)`

=735-42.2=692.8 mmhg

Now

By using combined gas law equation:

`(P_1*V_1)/(T_1) =(P_2*V_2)/(T_2)`

`V_2=(P_1*)/(P_2)*(T_2)/(T_1) *V_1`

`V_2=(P_gas)/(P_2)*(T_2)/(T_1) *V_1`

Here
`P_2 \:and\: T_2` are standard pressure and temperature respectively.

we have

`P_2=750mmhg \:and\: T_2=273K`

Substituting value, we get

`V_2=(692.8)/(750)*(273)/(308) *250`

`V_2= 819.51 ml`