Oxidation, Equilbria, Kinetics

Question 1

What is the Activation Energy?

Answer 1

The activation energy is the minimum amount of energy that particles require in order for a successful collision to occur

Question 2

Rate Of Reaction

Answer 2

The rate of reaction is the change in the amount or concentration of a reactant or product over time.

Question 3

What factors influence the rate of reaction?

Answer 3

The rate of reaction is influenced by many factors, including:

Temperature
Concentration
Pressure
Surface Area
Presence of Catalysts

Question 4

How does Surface Area influence the rate of reaction?

Answer 4

• Increasing surface area of reactants increases the surface that is exposed to other particles and hence to possible collisions.
• The number of collisions that can take place at any one time increases.
• Therefore, increasing the surface area of a solid reactant increases the rate of the reaction.

Question 5

Parts of the Maxwell Boltzman Distribution

Answer 5

Area under curve – the area under the curve is a measure of the total number of particles present.

Activation energy – A dotted line or straight line is used to represent the activation energy.

Shaded region – the shaded region to the right of the activation energy line represents the only particles that will react when they collide. These are the particles that have sufficient energy that is more than the activation energy.

Median (most common) particle energy – the peak of the curve represents the most common/likely energy of any single particle in the reaction.

Question 6

Catalyst

Answer 6

A catalyst is a substance that increases the rate of a chemical reaction without being changed in chemical composition or amount.

Question 7

Benefits of Catalyst usage

Answer 7

• lower production costs
• can improve properties of reaction products
• can reduce waste production because better atom economy
• more sustainable because allows for reactions to be done at lower temperatures and pressures

Question 8

How does concentration influence rate of reaction?

Answer 8

• An increased concentration means more particles for a fixed volume.
• more particles closely packed together
• closer together so can collide more frequently
• Increase in no. of successful collisions.

Question 9

How does pressure influence rate of reaction?

Answer 9

• An increased pressure means more particles for a fixed volume.
• more particles closely packed together
• closer together so can collide more frequently
• Increase in no. of successful collisions.

Question 10

Collision Theory

Answer 10

• For a reaction to occur the particles involved must collide in the correct orientation with a sufficient energy.

Question 11

How does temperature influence rate of reaction?

Answer 11

• An increase in temperature causes particles in a reaction to move faster as they gain more kinetic energy. The average speed of the particles increases.
• As the particles gain more kinetic energy, a greater proportion of these particles have energy more than the activation energy., so more can react.
• thus Increased in no. of successful collisions

Question 12

What is a reversible reaction?

Answer 12

reaction that occurs in both directions

• The direction in which the reaction goes depends on its conditions.

Question 13

Dynamic Equilibrium

Answer 13

• When the forward reaction is happening at the same RATE as the backward reaction
• At equilibrium the quantities/concentrations of reactants and products remain constant
• A dynamic equilibrium only occurs for a reversible reaction in a closed system

Question 14

Le Chatelier’s Principle

Answer 14

If a dynamic equilibrium is disturbed by a change in conditions (temp,conc,F/A) then the position of equilibrium will shift to counteract the change.
This principle can be used to maximise percentage yields in industry.

Question 14

Closed System

Answer 14

A system where nothing can be added or removed other than energy.

Question 15

Haber Process

Answer 15

N2 + 3H2(G) <> 2NH3
conditions –> 400-450°C, 200atms

optimal conditions:
need to compromise conditions
to shift equilbirum - low temp, high atms
rate of reaction - high temp, high atm
financial cost - low temp, low atm

Question 16

Effects of Temperature on Kc

Answer 16

• The value of Kc will change if the temperature is changed as the temperature change will affect the direction in which the reaction goes.
• An increase in Kc is dependent on an increase in product which will depend on what direction the reaction is in.
  (same for decrease)

Question 17

Effects of Concentration on Kc

Answer 17

Kc is unchanged.

Question 18

Effects of a Catalyst on Kc

Answer 18

Kc is unchanged

• speeds up rate of reaction so equilibrium will be reached faster

Question 19

Position of Kc

Answer 19

Kc = 1 <- same concentration of reactants and products
Kc > 1 <- position of equilibrium is shifted to the right
Kc < 1 <- position of equilibrium is shifted to the left

Question 20

finding Kc with homogeneous & heterogeneous reactions

Answer 20

• Equilibrium constant only works for homogeneous reactions (all products and reactants are in the same phase)
  however:
  S + L <- can calculate Kc but must ignore solid
  S+ G <- can calculate Kc but must ignore solid
  L + G <- cannot calculate kc but can find Kp

Question 21

What happens to the amount of product formed when there is an increase in concentration of reactants in a reversible reaction?

Answer 21

• increased reactants
• equilibrium shifts to the left
• thus more product formed from excess reactant
  (opposite for if concentration decreases)

Question 22

What happens to the amount of reactant formed when there is an increase in concentration of products in a reversible reaction?

Answer 22

• increased product
• equilibrium shifts to the right
• thus more reactant formed from excess product
  (opposite for if concentration decreases)

Question 23

What happens to the reactants and products of a reversible reaction when the pressure is increased?

Answer 23

• increased pressure
• equilibrium will shift to side of fewest moles
• equilibrium will be restored due to lower pressure again by shifting to the side of fewest moles

Question 24

What happens to the reactants and products of a reversible reaction when the pressure is decreased?

Answer 24

• decreased pressure
• equilibrium will shift to side of greatest moles
• equilibrium will be restored due to greater pressure again by shifting to the side of the greatest moles

Question 25

What happens to a dynamic equilibrium when temperature is increased?

Answer 25

• shifts to the endothermic direction
• endothermic reactions requires heat so will remove excess heat from the system

Question 26

What happens to a dynamic equilibrium when temperature is decreased?

Answer 26

• shifts to the exothermic direction
• exothermic reactions release heat so will add extra heat to the system to restore balance.

Question 27

What is disproportionation?

Answer 27

When an element in a single species in a chemical reaction is simultaneously being oxidised and reduced.

e.g chlorine
Cl2 + 2NaOH –> NaCl(aq) + NaClO + H2O
0 -1 +1

Question 28

what is a redox process?

Answer 28

When both reduction and oxidation happen simultaneously.

Question 29

When are Oxygen, Hydrogen and Chlorine’s oxidation numbers different?

Answer 29

Oxygen is -1 for peroxides, Hydrogen is different for metal hydrides, and chlorine when bonded with fluorine and oxygen.