Question

Hi! Need help on a question:

A 65.0 L stainless steel container was charged with 1.00 atm of hydrogen gas and 2.00 atm of oxygen gas. A spark ignited the mixture, producing water. What is the pressure in the tank at a constant temperature of 25°C?

I got 1.50 atm for this part - this was correct!
This is the part I need help with:

What is the pressure in the tank, starting with the same pressures of gases, at a constant temperature of 125°C?

Answer 1

Quick question. Is the 1.5atm you calculated, the value for the pressure of the water vapour after combustion or before combustion?

Answer 2

After combustion!

Answer 3

okay, not 100% sure on this answer but whatever.

Pressure is directly proportional to temperature (P=kT)

where k is a constant of the gases above.
where T is the temperature in kelvin.


So first calculate k for the first part

k = P/T.
k= 1.5atm / (273+25) (273 + 25) is temperature in kelvin
k= about 0.005

then use this constant to calculate the pressure in the second part.

P = kxT
P = 0.005 x (273 +125)
P=1.99 atm.

I used rounded values thought so be careful.

Answer 4

just use P1/T1=P2/T2
the volume is constant and the number of moles too