PRELIMINARY COURSE ASSESSMENT

CHEMISTRY:

REACTION RATES

PART A

PART B

PART C

BIBLIOGRAPHY

TEAM MEMBERS

GUEST BOOK

ABOUT

Page: 5 of 10 (* currently answering part (a) )

Remarks

There are four ways of speeding up reactions that is increasing the number of particles colliding with each other.

The closer the reactants are together the more often they will collide. For example we know that charcoal in a barbecue burns much faster when fanning it. This is because a higher concentration of oxygen in the air is reacting with the charcoal. We call this type of reaction, combustion.

  Consider the reaction,

  Mg + HCl ® MgCl₂ + H₂

Magnesium can only react with the HCl molecules on its surface. But if we make Mg into a powder, the HCl can get around each little grain in the powder, increasing the number of collisions and therefore speeding up the reaction.

The higher the temperature the collisions between the particles in solution would be faster and more violent. Bonds are more likely to break and the reactions are therefore faster.

That is why foods are kept in fridges to slow down the decomposition process.

Catalysts are substances, which speed up some reactions. They are not used up by the reactions and can be recovered and used once again once the reaction is over.

They are particularly useful when the uncatalysed reaction has a very high activation energy (and is therefore very slow). The catalyst usually provides a pathway of lower activation energy.