rates of reaction

What is meant by ‘rate of reaction’?

how quickly reactants are turned into products

Formula for calculating rate of reaction (2)

• mass of product / time taken

• volume of product / time taken

3 different ways of measuring rate of reaction

• precipitation and colour change

• change in mass

• volume of gas gained or lost

How can precipitation and colour change be used to measure rate of reaction (3)

p: measure time it takes for mark e.g cross under flask to disappear

c: measure time it takes for colour to change

(1 / time taken)

2 issues with measuring rate of reaction from precipitation and colour change

• subjective

• cant use the results for a rate of reaction graph

How can you calculate rate of reaction from a change in mass? (4)

• balance to measure how mass changes over time

• measure at regular intervals

• plot results on graph

• draw tangent to find rate a particular time

Most accurate way to measure rate of reaction + Why?

change in mass because balance is the most accurate measuring device

How can you use a gas syringe to measure rate of reaction? (4)

• use syringe to measure how the volume changes over time

• measure at regular intervals

• plot results on graph

• draw tangent to find rate at a particular time

4 factors that affect the rate of a chemical reaction

• concentration/gas pressure

• temperature

• catalyst

• surface area

How does increasing temp affect rate of reaction? (4)

• particles move faster because they have more kinetic E

• so collide more frequently

• collide with more energy

• collision is more likely to have enough energy to react (ea)

How does increasing concentration/gas pressure affect rate of reaction? (2)

• number of particles per unit volume will increase

• increases frequency of collisions

How does increasing the surface area affect rate of reaction? (2)

• for the same volume of solid, particles will have a greater area to collide on

• increases frequency of collision

What is collision theory?

for particles to react, they have to collide with sufficient energy and at the right direction/orientation

Why do particles need activation energy?

they need energy to break the bonds of the reactants so that the reaction can begin

On a concentration/time graph of a chemical reaction, what does a steep gradient of the line indicate?

reaction was fast

Why do concentration/time graphs plateau?

plateaus as the reactants are used up