equilibrium question?

Question

Let's say I have H2+I2----->2HI
volume is 1L
atm's are .5H, 1atm I and 5.2atm's HI
temp is 0 celcius

I have the equlibrium constant formule (products over reactants), but how do i get the values to plug in?

Answer 1

If your expression for the equilibrium constant is Kp, you just plug the pressures of the individual gases into the equation.

If you expression for the equilibrium constant is Kc, you'll need to calculate the individual concentrations. You can use the ideal gas law with the pressure of each gas, the volume, you've got the temperature (convert it to K) and the gas constant. Calculate the number of moles of each gas present. Since your container is 1 L, the concentration of each gas (in mol/L) will just be the number of moles of each gas divided by 1 L. Then, plug those concentrations into your expression for Kc and calculate the value.