Chemistry - Kinetics

What does the collision theory state?

That in order for a reaction to occur particles must collide with enough energy and in the correct orientation.

What is an ineffective collision?

When particles collide in the wrong orientation and with not enough energy and so bounce off each other without causing a chemical reaction.

What is collision frequency?

The number of collisions per unit time.

What is activation energy?

The minimum amount of energy required for particles to collide and start the reaction.

Why is the activation energy in endothermic reactions usually higher than in exothermic reaction?

In exothermic reactions the reactants are higher in energy than the products, whereas in endothermic reactions the products are higher in energy than the reactants.

What is a catalyst?

A substance that speeds up the rate of reaction without being used up.

How do catalysts increase the rate of a reaction?

They provide a different reaction pathway by lowering the activation energy.

Draw and label a Maxwell-Boltzmann curve.

What does the area under the Maxwell-Boltzmann distribution curve show?

The total number of molecules in a sample.

What does the Maxwell-Boltzmann distribution curve show?

It's a graph that shows the distribution of energies at a certain temperature. It shows that only a few molecules in a sample have enough energy for a successful collision.

What happens to rate of reaction when temperature is increased?

The kinetic energy of the particles increases, causing the particles to move around faster resulting in more frequent collisions. And so increasing rate of reaction.

How does the Maxwell-Boltzmann distribution curve change when temperature is increased?

This means that the proportion of successful collisions also increases. within the Maxwell-Boltzmann distribution the curve flattens and the peak shifts to the right. This means that the proportion of successful collisions also increases. within the Maxwell-Boltzmann distribution the curve flattens and the peak shifts to the right.

What is the effect of concentration on rate of reaction?

Increasing concentration means that there are a greater number of particles in a given volume, this leads to a greater frequency of collisions and so an increased rate.

What is the effect of pressure on rate of reaction.

When the pressure is increased the molecules have less space to move around without collisions happening, this increases the frequency of collisions per unit time but also the frequency of successful collisions and thus increases rate of reaction. The Maxwell- Boltzmann distribution is shifted to the right.

What is catalysis?

The process in which the rate of reaction is increased by a catalyst.

What does the Maxwell-Boltzmann distribution look like with a catalyst.

Within the Maxwell-Boltzmann distribution the curve flattens and the peak shifts to the right.