Chapter 7. Equilibria

Question 1

State Le Chatelier’s principle and give the different scenarios

Answer 1

If a change is made to a system at dynamic equilibrium, the position of equilibrium moves to minimise this change.
1. An increase in concentration will favor a reaction in which the concentration of that substance is reduced.
2. Pressure
-Only applicable to gases
-An increase in overall pressure will favor a reaction that produces less moles.This is because less moles per unit volume will exert less pressure. The opposite is true fro decrease in pressure.
3. Temperature
-An increase in temperature will favour a decrease in temprature(endothermic)
4. Catalysts
-No effect on the position of the equilibrium

Question 2

Note

Answer 2

Partial pressure is given by mole fraction(moles of the gas/total number of moles of the gases)

Question 3

pH formula

Answer 3

pH = -log₁₀[H⁺(aq)]

Question 4

What is a strong acid?

Answer 4

An acid that completely disociates into ions in an aqueous solution

Question 5

Common acid formulas

Answer 5

HCl ==> Hydrochloric acid
HNO₃ ==> Nitric
H₂SO₄
CH₃COOH ==> ethanoic(acetic)

Question 6

What is an acid and a base?

Answer 6

An acid is a proton doner(H^{+</sup) and a base is a proton acceptor}

Question 7

Note

Answer 7

A solution is neutral when [H⁺] = [OH^-]

Question 8

Note

Answer 8

Make sure you know how to calculate Kc and Kp

Question 9

Note

Answer 9

Acronym IREE
Initial moles
Reacting moles
Equilibrium moles
Equilibrium concentration

-Moles of reactants at equilibrium = initial moles - reacting moles
-Moles of products at equilibrium = initial moles + reacting moles

Question 10

Note

Answer 10

Haber process
-Conditions – 450⁰C, 200atm and iron catalyst
-Ammonia – N₂ + H₂

Contact process
-Conditions – 450⁰C, 1-2atm and vanadium(V) oxide
-Sulfuric acid – Sulphur and oxygen
S + O₂ –> SO₂
<b>2SO₂ + O₂ –> 2SO₃</b>
SO₃ + H₂SO₄ –> H₂S₂O₇(oleum)
Oleum + water –> Sulfuric acid
Uses of sulfuric acid
1. To make fertilisers such as ammonium sulfate.
2. As a battery acid, in electroplating, refining oil and in chemical industries.
3. To make detergents, soaps, explosives, dyes, paints, plastics and man-made fibre.

Question 11

Note

Answer 11

The removal of a proton from an acid produces its conjugate base
HCl —> H⁺ + Cl^-(conjugate base)
The reception of a proton by a base produces its conjugate acid
NH₃ + H⁺ —> NH₄⁺