Question

H2 (g)+I2 (g)↔2HI(g)

Calculate ΔG for the system at 700 K when the concentrations are [H2] = 0.12M, [I2] = 0.27M, and [HI] = 0.118M.

What would be my first step? If I make an ICE chart, what would I do from there? I just need the first step to help me out :(
THANKS!

Answer 1

I assume this is not at equilibrium. If that is the case, then
dG = dGorxn + RTlnQ
dGorxn you obtain from
dGorxn = *n*dGo formation products) - (n*dGo formation reactants)

Then Q is (HI)^2/(H2)(I2)

Answer 2

Dr. Bob, as grateful as I am you took the time to answer my question, I do not believe you are right. In order to get Q, it needs to be in atm, and I am dealing with M?

if I am wrong, can you explain to me what I would need to do next?

Answer 3

Why must you use atm? You use atm for gases and when you have pressures, these aren't gases so you use molarity. Calculation of Q occurs for either. In fact, one may use, if the situation occurs, a mix where pressure is used for the gas ad molarities for the solutions. For example,
Zn(s) + 2H^+(aq) ==> Zn^2+(aq) + H2(g)
Q for that rxn is (Zn^2+)*pH2/(H^+)^2
The Zn^2+ and H^+ are substituted in M and pH2 in atm.
However, if you feel uncomfortable with this, please do seek a second opinion.

To proceed with the problem, first calculate dGorxn from the equation I provided above, substitute the concns and calculate Q, then plug that into the dGrxn = dGo + RTlnQ and solve for dGrxn Good luck.