For the following reaction:
2NH3 ----> N2 + 3H3
6.42 moles of NH3 were placed in a 7.4 L flask and allowed to come to equilibrium. 3.60 moles of NH3 remain at equilibrium. Calculate Kc for the reaction.
Set up an ICE chart, substitute into Kc and solve.
would you have to change the moles of NH3 to atm?
No. The question asks for Kc, not Kp. You may work in concn (molarity)from the beginning OR you may work in moles until the stoichiometry is finished, convert moles of each material to molarity and plug into the Kc expression.
To calculate the equilibrium constant, Kc, for the given reaction, we need to use the concentration of the reactants and products at equilibrium.
Step 1: Calculate the initial concentration of NH3:
Given that 6.42 moles of NH3 were placed in a 7.4 L flask, we can calculate the initial concentration of NH3 using the formula:
Initial concentration = moles / volume
Initial concentration of NH3 = 6.42 moles / 7.4 L
Step 2: Calculate the equilibrium concentration of NH3:
Given that 3.60 moles of NH3 remain at equilibrium, we can calculate the equilibrium concentration of NH3 using the same formula:
Equilibrium concentration = moles / volume
Equilibrium concentration of NH3 = 3.60 moles / 7.4 L
Step 3: Calculate the equilibrium concentrations of N2 and H2:
Since the stoichiometric coefficients of N2 and H2 are different from that of NH3, we need to consider the changes in moles to determine their equilibrium concentrations.
From the balanced equation, 2 moles of NH3 produce 1 mole of N2 and 3 moles of H2. Therefore, we can calculate the equilibrium concentrations of N2 and H2 using the formulas:
Equilibrium concentration of N2 = (initial concentration of NH3 - equilibrium concentration of NH3) / 2
Equilibrium concentration of H2 = (initial concentration of NH3 - equilibrium concentration of NH3) / 3
Step 4: Calculate the equilibrium constant (Kc):
The equilibrium constant (Kc) is calculated using the formula:
Kc = (concentration of products) / (concentration of reactants)
In this case, the concentration of the products is [N2]^1 * [H2]^3, and the concentration of the reactant is [NH3]^2. Plugging in the values we calculated in the previous steps:
Kc = ([N2]^1 * [H2]^3) / ([NH3]^2)
Now, you can substitute the calculated concentrations into the formula and solve for Kc.