A chemical system within a sealed 1 L reaction vessel is described by the following reversible reaction equation:
2H2S(g) <---> 2H(g) + S2(g)
If the equilibrium constant is 0.000 004 200 at 1103 K find:
(a) the reaction quotient intially
(b) the order of concentration of all three components at equilibrium without using calculations
(c) what the size of the reaction quotient indicates regarding the extent of the forward reaction
(d) the quilibrium concentration of sulphur gas if 0.070 mol of hydrogen sulphide gas is intially placed in the vessel
So far I did a), b) and c) but for d) this is how much I did so far:
However, when I plug in the x value into the equation, I don't get the Keq value given to me. In other words the equation isn't LS=RS. Any help?
Thanks in adavance
First, I think you made a typo. I assume you meant to write
H2S ==> 2H2 + S2
Second, you need to explain to me how you obtained a,b,c without any numbers. You need numbers to calculate a reaction quotient. Why didn't you provide your answer and what you did. That way I could check it. As it is I'm in the dark as to what you did.
But here is how you do d.
..........2H2S ==> 2H2 + S2
I........0.07M......0.....0
C.........-2x.......2x....x
E........0.07-2x....2x....x
Substitute the E line into the Keq expression and solve for x = (S2)
This is a cubic equation and when I solved it I obtain about 0.0017 M for S2. I used a calculator on the web to solve the cubic. It works reasonably well I think.
Hello There
How I did a) was that I know that the equation for the reaction quotient was products/reactants. In this situation however, since I already have 0 moles of both products it would immediately mean that any number divided by 0 is 0.
For b), the question is also asking me to grade the concentrations from highest to lowest. So since I know that the Keq is a very small number, then that must mean that the reactants must also be a very small number. Next since it takes 2 moles of hydrogen gas for each sulfur gas, that tells me that the greatest is H2 then S2 then H2S
For c) Since I know the reaction quotient is 0 then that means that the forward reaction is very minimal or even close to not occurring.
Secondly:
For d)..... the Keq expression is [H2]^2[S2]/[H2S]^2 correct?
However, when I reach the part 4x^3/0.0049-0.28x+4x^2 I am stuck. Any help would be appreciated.
To calculate the equilibrium concentration of sulfur gas (S2) in the reaction vessel, you need to use an ICE table and make some assumptions. Here's the step-by-step process:
Step 1: Write the balanced equation for the reaction:
2H2S(g) ⇌ 2H(g) + S2(g)
Step 2: Define the equilibrium concentrations as x for H2S, y for H, and z for S2.
Step 3: Set up the ICE (initial, change, equilibrium) table:
| | H2S | H | S2 |
|----------|-------|-------|-------|
| Initial | 0.070 | 0 | 0 |
| Change | -2x | +2x | +x |
| Equilibrium | 0.070 - 2x | 2x | x |
Step 4: Use the equilibrium concentrations in the equilibrium expression:
K = [H]^2 * [S2] / [H2S]^2 = 0.000004200
Step 5: Substitute the equilibrium concentrations from the ICE table into the equilibrium expression:
0.000004200 = (2x)^2 * x / (0.070 - 2x)^2
Step 6: Solve the equation for x:
Multiply both sides by (0.070 - 2x)^2:
0.000004200(0.070 - 2x)^2 = (2x)^2 * x
0.000004200(0.0049 - 0.28x + 4x^2) = 4x^3
0.002058 - 0.1176x + 0.0084x^2 = 4x^3
At this point, you would need to solve the cubic equation for x using numerical methods or software. Once you find the value of x, you can calculate the equilibrium concentrations of all three components using the equations from the ICE table.
However, since you mentioned that the equation is not balanced, it's important to recheck the stoichiometric coefficients and make sure you are using the correct equilibrium constant (Keq) value.
To solve part (d) of the question, you need to use the equilibrium expression and the given initial concentration of hydrogen sulfide gas to determine the equilibrium concentration of sulfur gas.
The equilibrium constant expression for the reaction is:
K_eq = [H]^2 * [S2]/[H2S]^2
Given that the equilibrium constant (K_eq) is 0.000004200, you can set up the expression:
0.000004200 = ([H]^2 * [S2])/([H2S]^2)
Now, let's assume that the change in concentration of hydrogen gas ([H]), sulfur gas ([S2]), and hydrogen sulfide gas ([H2S]) at equilibrium is x. Since there are stoichiometric ratios in the balanced equation, the changes in concentration will be 2x for [H] and [S2] and -2x for [H2S].
So, you can substitute the concentrations at equilibrium:
[H] = 2x
[S2] = 2x
[H2S] = 0.07 - 2x (initial concentration of [H2S] minus the change)
Substituting these values into the equilibrium expression, you get:
0.000004200 = (2x)^2 * (2x) / (0.07 - 2x)^2
Simplifying this equation will give you a cubic equation, which you can solve to find the value of x. Once you find the value of x, substitute it back into the expressions for [H], [S2], and [H2S] to find the equilibrium concentrations of the gases.
At equilibrium, the equilibrium concentrations of [H], [S2], and [H2S] will be proportional to the coefficients in the balanced equation. So, without doing any calculations, you can determine the order of the concentrations as follows:
Order of concentration of H: 2
Order of concentration of S2: 2
Order of concentration of H2S: -2
Finally, note that the equilibrium constant, K_eq, indicates the extent of the forward reaction. If K_eq is very large, it means the forward reaction is favored and has a high yield of products at equilibrium. If K_eq is very small, it means the reverse reaction is favored and has a high yield of reactants at equilibrium. In this case, K_eq is quite small (0.000004200), indicating that the reverse reaction (2H(g) + S2(g) --> 2H2S(g)) is favored.