Urgent Help - Chemistry Questions : Factors affecting the Rate of reactions

Question

Please some one to help me with this 4 questions :

1. Why the rate of reaction depends upon the concentration of the reactants ?

2.How the change in concentration affect the rate of change?

3.''Why'' an increase in temperature leads to a change in the rate of reaction.

4. Fully describe ''how'' an Increase in temperature affects the rate of reaction .

Please someone to help me with this questions.

Thanks Peter from Sydney

Answer 1

It all comes down to "collision theory".  Before a chemical reaction can take place two molecules must collide.  Anything that increases the rate at which molecules collide will increase the rate of reaction.

Increasing the concentration will increase the number of molecules in a space and increase the number of collisions.  Increasing the temperature will increase the speed at which the molecules are moving and increase the number of collisions.  

Others are the surface area, or particle size.  The smaller the particle size or greater the surface are the greater the number of collisions.

Rate is sped up with a catalyst.  A catalyst is a substance that doesn't appear to be used up in a reaction.  A catalyst provides a different reaction pathway with a lower activation energy.  This has the effect of allowing more collisions to produce the products which speeds up the reaction.