Rates of Reaction and Energy changes

To find the rate of a reaction, what else must you measure as well as either the amount of product made or the amount of reactant used up?

The time taken.

What three ways can we use to monitor the rate of a reaction that produces a gas?

Weigh the reaction mixture to see how quickly it decreases. Collect the gas in a gas syringe to see how quickly it is produced. Collect the gas over water in an inverted measuring cylinder to see how quickly it is produced.

If a graph of rate against concentration gives us a straight line which goes through the origin, how do we describe this relationship?

Directly proportional.

What is activation energy?

The minimum energy required to cause a reaction when particles collide.

What five things can affect the rate of a reaction?

Surface area, concentration, pressure (only for reactions between gases), temperature, catalyst.

Give two ways that you could increase the surface area of a solid in a reaction?

Use a greater mass of the solid, Use smaller sized pieces of the solid.

Why does increasing the surface area of a solid increase the rate of a reaction?

There will be more frequent collisions because there is a larger surface more the particles to react with

Why does increasing the concentration of a solution increase the rate of a reaction?

There will be more particles per centimetre cubed and so there will be more frequent collisions between particles.

Why does increasing temperature increase the rate of a reaction?

The particles will have more kinetic energy so they will move more quickly and so there will be more frequent successful collisions. Also, a greater proportion of the collisions will have energy over the activation energy.

What is a catalyst?

A substance that increases the rate of a reaction but is not used up in the reaction.

How does a catalyst increase the rate of a reaction?

It provides a different route for the reaction with a lower activation energy, so that a greater proportion of particles can cause a reaction when they collide.