[dmk007]

In the manufacture of ammonia, a mixture of nitrogen and hydrogen in the proportion of one to three by volume at a pressure of 60 atmospheres and at a temperature of 450K gave an equilibrium mixture containing 12% ammonia. Calculate Kp at this temperature.

[Astrokel]

Write out the reversible reaction equation and ICE table.

[dmk007]

still don't understand

[Astrokel]

It's almost the same as the other question you posted, try it out first 

[dedanh]

In the manufacture of ammonia, a mixture of nitrogen and hydrogen in the proportion of one to three by volume at a pressure of 60 atmospheres and at a temperature of 450K gave an equilibrium mixture containing 12% ammonia. Calculate Kp at this temperature.

hi ,

n_before = 1 mol , V = const

       N_2(g)     +      3H_2(g)     <==>     2NH_3(g)
bf    0,25             0,75                    0
[]    0,25 - x       0,75 - 3x               2x

n_after = 0,25 - x + 0,75 - 3x + 2x = 1 - 2x

PV = nRT
---> P₁V = 1.0,082.450  ---> V = 36,9 : 60 = 0,615 (l)
---> P₂V = (1 - 2x).0,082.450
---> P₂.0,615 = (1 - 2x).36,9

'cause n_NH3 = 12% . n_after = 12%(1- 2x)
---> 2x = 12%(1-2x)
---> x
---> K_p = (2x)²/{(0,25-x)(0,75-3x)³}

K_p = 0,286

is that true   

[dmk007]

The answer was given as 6.324 x 10^-5

[dedanh]

oh , i'm wrong  

in ICE table , i have to divide for V

x = 0,0536 mol

---> K_p = {(2x/0,0615)²}/{(0,25-x)(0,75-3x)³/(0,615)⁴}

K_p  = 0,62


why i can't edit my post  

but    , can't u check my post , hope u will find my mistake

good morning but in my country , i say good night   

[Astrokel]

I got 7.93 x 10^-5, hmm..

[vhpk]

I think that the decrease in pressure leads to the decrease in volume and versus ( in this case). Hence, with the rate 1:3 in volume, deduce to the rate 1:3 in pressure, call x as the volumes of N2 has reacted then we can calculate it then imply to the Pressure constant.
Kp = P_N2xP_H2³/P_NH3²
But in fact, the result I get was similar to Astrokel. I'm wondering whether there is any limitations to the significant digits.
@dedanh: the data above doesn't give you any data about the moles, you can't assume the original mole number is 1 and use the ideal gas equation. Moreover, remember you can't neglect the Van der Waals force in low temperature and high pressure