Question

What pressure is needed to compress 455ml of oxygen gas at 2.50 atm to a volume of 282ml?

Answer 1

Explanation: To obtain the gas pressure, subtract the vapor pressure of water from the total pressure. EXAMPLE: A 325 mL sample of gas is collected over water at 26oC and 742 mm Hg pressure. Calculate the volume of the dry gas at STP. The vapor pressure of water is 25 mm Hg at 25oC.

Answer 2

As per Boyle’s law

For a given amount of gas, Pressure is inversely proportional to its volume, at constant temperature

The expression for Boyle’s law is given by

`P \propto  \frac {(1 )}{V}` (at constant T)

`PV=k`(k is the constant)

when there is a change in pressure and volume we make use of the expression

`P_1 V_1=P_2 V_2`

`P_1` and
`V_1` are the initial pressure and initial volume and

`P_2` and
`V_2` are the final pressure and final volume

`P_1=2.50atm\\\\V_1=455ml\\\\P_2=? atm\\\\V_2=282ml`

`P_1 V_1=P_2 V_2`

Plugging in the values

`2.50atm * 455ml = P_2 * 282ml`

`P_2 = \frac {(2.50atm*455ml)}{282ml} \\\\=4.03 atm`

(Answer)