Question

A 0. 0688 mol sample of no2(g) is placed in a rigid 1. 00 l reaction vessel and allowed to reach equilibrium at a certain temperature. What is the value of kc at this temperature if 0. 0133 mol of n2o4(g) is present at equilibrium?.

Answer 1

12.5

Step-by-step explanation:

Step 1: Write the balanced equation

2 NO₂(g) ⇄ N₂O₄(g)

Since the reaction takes place in a 1.00 L vessel, the initial concentration of NO₂ is 0.0300 M and the concentration at equilibrium of N₂O₄ is 0.00500 M.

Step 2: Make an ICE chart

2 NO₂(g) ⇄ N₂O₄(g)

I 0.0300 0

C -2x +x

E 0.0300-2x x

Step 3: Find the value of x

Since [N₂O₄]eq = 0.00500 M, x = 0.00500

Step 4: Calculate the concentrations at equilibrium

[NO₂] = 0.0300-2(0.00500) = 0.0200 M

[N₂O₄] = 0.00500 M

Step 5: Calculate the concentration equilibrium constant (Kc)

Kc = [N₂O₄]/[NO₂]²

Kc = 0.00500/0.0200²

Kc = 12.5

Answer 2

17.4

Step-by-step explanation:

The chemical equation for the reaction is:

2NO2(g) ⇌ N2O4(g)

At equilibrium, we are given that the number of moles of N2O4 is 0.0133 mol. From the balanced chemical equation, we can see that 2 moles of NO2 react to form 1 mole of N2O4. Therefore, the number of moles of NO2 present at equilibrium is:

(0.0688 mol - 0.0133 mol)/2 = 0.02775 mol

The expression for the equilibrium constant, Kc, for the reaction is:

Kc = [N2O4]/[NO2]^2

Substituting the values we have calculated:

Kc = (0.0133 mol)/(0.02775 mol)^2 = 17.4 (rounded to one significant figure)

Therefore, the value of Kc at this temperature is 17.4.

Note: why should put this ^2

The square in the expression for the equilibrium constant, Kc, is because the stoichiometric coefficients in the balanced chemical equation for the reaction involve the reactants and products in a 2:1 ratio.

The equilibrium constant expression is defined in terms of the concentrations (or partial pressures) of the reactants and products at equilibrium, raised to the power of their stoichiometric coefficients. For this reaction, the stoichiometric coefficients are 2 for NO2 and 1 for N2O4. Therefore, the concentration of NO2 needs to be raised to the power of 2 in the equilibrium constant expression, as shown below:

Kc = [N2O4]/[NO2]^2

This is because the concentration of NO2 appears twice in the balanced equation. The square is used to ensure that the units in the numerator and denominator of the Kc expression match. It is a way of adjusting the concentration of NO2 to account for the fact that it appears twice in the equation.

ALLEN