5.1 Collision theory

Question 1

What needs to occur in order for two things to react

Answer 1

They need to collide with enough force to break the bonds.
Collision must take place between parts of the molecule that will react

Question 2

How does increasing temperature affect rate of reaction

Answer 2

It increases the speed of molecules so increases their energy so there are more successful collisions

Question 3

How does increasing concentration of solution affect rate of reaction

Answer 3

If there are more particles present in a given volume then collisions are more likely to occur and rate of reaction is faster

However as reaction proceeds, the reactants are used up and their concentration falls so in most reactions rate of it falls as reaction goes on

Question 4

How does increasing pressure in a gas reaction affect rate of it

Answer 4

Same as increasing concentration of solution: more molecules in a given volume so more collisions

Question 5

How does increasing surface area of solid reactants affect rate of reaction

Answer 5

The greater the surface area, the more of its particles are available to collide with molecules in a gas or liquid.

So breaking a solid lump into smaller pieces increase rate of reaction as there are more sites for reaction

Question 6

How does using a catalyst

Answer 6

It is a substance that can change rate of reaction without being used up in reaction itself

Question 7

Describe exothermic reaction profiles

Answer 7

If there is a high activation energy, there is a steep upwards curve then long steep slope downwards.

The smaller upwards curve shows the activation energy that needs to be overcome in order for reaction to proceed

Question 8

What is a transition state or activated complex

Answer 8

When the activation energy has just been overcome so reaction is about to occur. It is unstable.

Question 9

Describe endothermic reaction profile

Answer 9

Products have more energy than reactants