Question

[13] Write the equilibrium mass balance expressions for the following equilibrium in terms of (a) KC and (b) KP.
4HCl(aq) + MnO2(s) ? Cl2(g) + 2H2O(l) + MnCl2(aq)

[14] At 700 K the rate constant for the reaction 2NO + O2 ? 2NO2 is 5.73

Answer 1

Hi,

13) First of all, when writing equilibrium constant expressions,
-It is always products over reactants.
-Make sure your chemical equation is balanced.
-The coefficient in the chemical equation=the exponent in the equilibrium constant expression.
-Kc is basically the same as Kp. But Kc is for concentration and Kp is for pressure. [X] is used to mean concentration of X. And I'll use P(X) to mean pressure of X.
-Pure solids and liquids are NOT included in the equilibrium constant expressions because their concentrations cannot change.
-The (aq) ones are not pure solids or pure liquids, so they are included.

Kc = [Cl₂] [MnCl₂] / [HCl]^4

Kp = P(Cl₂) XP (MnCl₂) / P (HCl)^4

14) Since this is a forward and reverse reaction,

Rate(forward) = 2 x Rate (reverse)

This is because 2 molecules of NO2 are consumed for every one molecule of O2

therefore,

Rate (reverse) = 5.73 x10^3 /2 = 2.865 X 10^3 M-2S-1