Question

Hydrogen gas is collected over water at 23.0 °C. The volume of the wet gas is 4.00 L at 737 torr.

What is the dry hydrogen gas volume at STP?

the answer on my answer key says 3.48 L. I have no idea how they got it, someone help me pls!

Answer 1

Given:

Volume of wet hydrogen gas (Vwet) = 4.00 L

Pressure (P) = 737 torr

Temperature (Twet) = 23.0°C = 296 K

To find:

Volume of dry hydrogen gas (Vdry) at STP (Tdry = 273 K and Pdry = 760 torr)

Solution:

Convert temperature to Kelvin: T = Twet = 23.0°C + 273 = 296 K

Use the combined gas law: P1V1/T1 = P2V2/T2

Plug in values: P1 = P, V1 = Vwet, T1 = T, P2 = Pdry = 760 torr, T2 = Tdry = 273 K

Solve for V2 (Vdry): Vdry = Vwet x Pdry x T / P x Tdry

Substitute values: Vdry = 4.00 L x 760 torr x 296 K / 737 torr x 273 K

Simplify: Vdry ≈ 3.48 L

Therefore, the volume of dry hydrogen gas at STP is approximately 3.48 L.

So the answer key is correct, but their method may have been incorrect.