Question

A 0.79 mole sample of HI is placed in a 5.000 liter container and held at a constant temperature until the gas-phase reaction

2 HI ⇀↽ H2 + I2

comes to equilibrium. At equilibrium, it is found that the concentration of I2 is 2.1×10−2 mol/L. What is the numerical value of the equilibrium constant Kc at this temperature?

Answer 1

To calculate the equilibrium constant Kc for the given gas-phase reaction, we need to determine the equilibrium concentration of HI using the concentration of I2 and the initial concentration of HI. Then we can use the equilibrium concentrations of HI and I2 to calculate Kc.

Step-by-step explanation:

The equilibrium constant, Kc, can be calculated using the concentrations of the reactants and products at equilibrium. In this case, we have the concentrations of I2 and the initial concentration of HI. The balanced chemical equation is 2 HI ⇀↽ H2 + I2.

Let's assume the concentration of HI at equilibrium is x M. Since 2 moles of HI react to form 1 mole of I2, the concentration of I2 at equilibrium can be calculated as (2x / 5.000 L) M = 2.1×10−2 mol/L. Solving for x, we can find the equilibrium concentration of HI.

Lastly, we can use the equilibrium concentrations of HI and I2 to calculate the equilibrium constant, Kc, by dividing the concentration of I2 by the concentration of HI squared.