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A dry gas occupies 136.5 cm^(3) at STP. ...

A dry gas occupies 136.5 `cm^(3)` at STP. If the same mass of the gas is collected over water at `27^(@)`C at a total pressure of 725 torr, what volume does it occupy? (The vapour pressure of water at `27^(@)C` is 25 torr.)

A

`157.3 cm^3`

B

`162.9 cm^3`

C

`159.2 cm^(3)`

D

`160.9 cm^(3)`

Text Solution

Verified by Experts

The correct Answer is:
B
At ` 27^(@)C, P_("dry gas")=P_("moist gas ") -P_("water vapour")=725-25=700` torr
Applying ,`(P_1 V_1)/(T_1) = (P_2 V_2)/(T_2)`
At STP , `P_1 = 760 ` torr , `P_2 = 700 ` torr , `V_1 = 136.5 cm^(3), V_2 = ?`
`T_2 = 273 K , T_2 =27^(@) C = (273 + 27) = 300 K`
`V_2 = (760 xx 136. 5)/(273) xx (300)/(700) = 162.9 cm^(3)`
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