What does it mean to describe a reaction as reversible when

Question

Chemical Equilibrium Assignment

Part 1 - Equilibrium Reactions

1. What does it mean to describe a reaction as "reversible"?

2. When writing an equation, how is a reversible reaction distinguished from a nonreversible reaction?

3. If a reaction is reversible, when can it be said to have reached equilibrium?

4. Is a system at equilibrium if the rate constants of the forward and reverse reactions are equal?

5. If the concentrations of products and reactants are equal, is the system at equilibrium?

Part 2 - Le Chateliers Principle

1. Suggest four ways in which the concentration of hydrazine, N2H4, could be increased in an equilibrium described by the following equation:

N₂(g) + 2H₂(g) ↔ N₂H₄(g)              ΔH = 95 Id

2. How will an increase in temperature affect each of the following equilibria? How will a decrease in the volume of the reaction vessel affect each?

(a) 2NH₃(g) ↔ N₂(g) + 3H₂(g)           ΔH = 92 Id
(b) N₂(g) + O₂(g) ↔ 2N0(g)              ΔH = 181 kJ
(c) 2O₃(g) ↔ 3O₂(g)                         ΔH = -285 kJ
(d) CaO(s) + CO₂(g) ↔ CaCO₃(s)       ΔH = -176 Id

3. Water gas is a 1:1 mixture of carbon monoxide and hydrogen gas and is called water gas because it is formed from steam and hot carbon in the following reaction: H₂O(g) + C(s) ↔ H₂(g) + CO(g). Methanol, a liquid fuel that could possibly replace gasoline, can be prepared from water gas and hydrogen at high temperature and pressure in the presence of a suitable catalyst.

(a) Write the expression for the equilibrium constant (Kc) for the reversible reaction

2H₂(g) + CO(g) ↔ CH₃OH(g)              ΔH = -90.2 kJ

(b) What will happen to the concentrations of H₂, CO, and CH₃OH at equilibrium if more H₂ is added?

(c) What will happen to the concentrations of H₂ CO, and CH₃OH at equilibrium if CO is removed?

(d) What will happen to the concentrations of H₂, CO, and CH₃OH at equilibrium if CH₃OH is added?

(e) What will happen to the concentrations of H₂ CO, and CH₃OH at equilibrium if the temperature of the system is increased?

(0 What will happen to the concentrations of H₂, CO, and CH₃OH at equilibrium if more catalyst is added?