Rates of reaction

Question 1

What is the rate of reaction

Answer 1

The rate of a chemical reaction is the speed with which reactants are converted into products

Question 2

Collision theory - explain how it works

Answer 2

• For a chemical reaction to occur, the reactant molecules must collide with enough energy to break bonds
• The more collisions there are per unit of time, the faster the reaction will be
• The minimum kinetic energy required for a reaction to occur is called the activation energy (Ea).
• As the reactant molecules collide they must have enough energy to overcome the repulsive forces (Caused by outer electrons) and start to break the bonds between atoms

Question 3

How to measure the rate of reaction?

Answer 3

• means measuring the change in amount of a reactant or the amount of a product
• the gradient of a graph is equal to the initial rate of reaction that that time

Question 3

What is the rate of reaction determined by?

Answer 3

• The rate of a reaction is determined by the number of effective collisions per second
• As the reaction progresses, the concentration of reactants decreases
• This reduces the frequency of collisions between particles and so the reaction slows down

Question 4

What are the factors that affect the rate of reaction, briefly explain

Answer 4

Temperature
Increase temperature = more energy (more force, move more quickly→more collisions) = reaction increase

Concentration
More concentration = more reactant moving (more collisions) = reaction increase

Particle size/surface area
Decrease particle size = increase surface are (more collisions) = faster reaction

Pressure
More pressure = smaller space (more collisions) = increase reaction

Catalyst
Are substances that change the rate of a reaction without being used up in the reaction
They never produce more product - they just produce the same amount more quickly
A catalyst can provide a surface for reactions to take place on.
Reactant molecules are held at a favourable angle for collisions to occur, increasing the likelihood of successful collisions.
Most of them lower the reaction’s activation energy

Stirring
As a chemical reaction proceeds, the particles of the reactants get used up. Hence, fewer collisions and the reaction slows down. Stirring helps the remaining reactants to collide.