WEEK10 - Topic 12

Chemical Equilibrium 

 

Part 1: Chemical equilibrium: Reversible reactions, Rates of reaction, Intro to chemical equilibrium

Learning Outcomes 1-2

Key Concepts

1. Reversible reactions
2. Rates of reactions
3. Chemical equilibrium

What Are Reversible Reactions?

Effective and ineffective Collision

What is Dynamic Equilibrium?

- 조건 : 1. reversible 2. closed system ( only energy can come in )

 

 

 

 

 

 

 

 

Part 2: Chemical equilibrium - Le Châtelier’s Principle: Effect of: Concentration, temperature, volume, & catalyst

Learning Outcomes: 3-6

Key Concept 

1. Le Châtelier’s Principle  

Le Châtelier’s Principle-effect of [Concentration], Volume (g) and temperature

By changing the concentration (adding more reactants), volume and pressure, and temperature,

yield can increase so the reaction can shift forward or backward.

 

Worked out Question- Temperature & Catalyst

-catalyst is a substance that influences the rate of reaction but can be fully recovered at the end of the reaction.

A catalyst does not shift the equilibrium or change the yield of either reactants or products.

A catalyst lower the energy of activation of the reaction and thus affects the rate of the reaction.

Activation energy is the minimum energy required for the reaction to occur.

 

 

 

 

Worked out Questions- Concentration & Challenge Question

 

 

 

 

 

 

 

 

 

 

Part 3: Chemical equilibrium - Equilibrium constants: Keq, Kw, Ka

 

Learning Outcomes: 7-8

Key Concepts 

1. Chemical equilibrium constants 

Kc or Keq

Please note that in this video they use Kc and we use both Kc and Keq. They are equivalent!

https://youtu.be/xfGlEXWDRZE

kc,keq are the equilibrium constant.

kc = [product]/[reactant]

 

Kw Introduction - The water ionisation constant 

H2O is not calculated in the equilibrium K because it is liquid.

Keq = Kc = equilibrium constant = > for water : kw : ionization constant of water 

kw = [H3O+][OH-] = 1.00 x 10-14 (It remains constant unless the temp changes)

https://youtu.be/Hm4wAqPr1JY

 

Kw- Ionisation of water in Acidic and Basic solution

https://youtu.be/o2Df3K6Qd2Q

 

Introduction to Ka for weak acids

https://youtu.be/ob0k6pG9r9Y

 

How to calculate Ka for a weak acid

https://youtu.be/PGJ6Svmkfnc

 

Ka to pH and Percent Ionisation

First step is to see whether it's strong acid or weak acid

It is a weak acid so we assume it hasn't ionised/ hydrolised that much -> assume 0.25-x ~0.25 !!!!!

(It is only available when the percent ionization is 5% or less!!!)

https://youtu.be/PGJ6Svmkfnc

Percentage of ionisation = [H3O+]/[acid]initial x 100%

 

 

Worked out questions Keq, Kw & Ka 

 

 

 

 

 

 

 

 

Part 4: Chemical equilibrium – Buffer solutions: Acid-Base Properties of Salts, pH of buffers

 

Learning Outcomes: 9-10
Key Concepts

1. The acidic & basic properties of salts
2. Buffer solutions

Acidic & Basic properties of salts

https://youtu.be/HwkEQfsJenk

Introduction to Buffers

https://youtu.be/8U5tP6GL9wM

 

 

Acid-base Equilibria & Buffer Solutions

https://youtu.be/jdmHjFp_35I

 

 

https://general.chemistrysteps.com/the-henderson-hasselbalch-equation/

The Henderson–Hasselbalch Equation - Chemistry Steps