Question

A 10-liter container is filled with 0.1 mol of H2(g)and heated to 3400 K causing some of the H2(g)to decompose into H(g). The pressure is found to be 4.0 atm . Part A Find the partial pressure of the H(g) that forms from H2 at this temperature. (Assume two significant figures for the temperature.)

Answer 1

Volume of container = 10 L
Amount of H2 = 1.0 mol

Temperature (T) = 3400 K

The pressure = 4.0 atm

Reaction of decomposition :

H2 (g) -- > 2 H(g)

I           0.1                   0

C          -x                     +2x

E          (0.1-x)             2x

Total number of moles = (0.1-x) + 2x = 0.1 – x + 2x

= 0.1-x

So total number of moles of gas = 0.1 –x

Total number of moles n = 0.1-x

We calculate number of moles by using ideal gas law.

pV = nRT

p is pressure in atm , V is volume in L , n is number of moles , R is gas constant

R = 0.08206 atm L / (K mol) , T =3400 K

n = pV/ RT = 4.0 atm x 10 L / ( 0.08206 L atm (Kmol)^-1 x 3400 K )

= 0.143 mols

Partial pressure of H = mol fraction of H x total pressure

Mol fraction of H = mol H / total mol

Mol H = 2 x
Total mol = 2x + (0.1-x)

0.143 = x + 0.1

x = 0.043

mol H = 2x = 2 * 0.043 = 0.086 mol H

Partial pressure = (0.086 / 0.143 )x 4.0 atm

= 2.40 atm