Question

Surface area affect the rate of reaction

Answer 1

The rate of reaction can be increased by increasing the surface area of one of the reactants, for example by making it into a powder. There is a risk of explosion in factories handlingcombustible powders such as custard powder. Catalysts are substances which change the rate of reaction but are unchanged at the end of the reaction.

Effect of surface area

The rate of a chemical reaction can be raised by increasing thesurface area of a solid reactant. This is done by cutting the substance into small pieces, or by grinding it into a powder. If the surface area of a reactant is increased:

More particles are exposed to the other reactantThere are more collisionsThe rate of reaction increases



Compared to a reaction with lumps of reactant, the graph line for the same reaction but with powdered reactant:

Has a steeper gradient at the startBecomes horizontal sooner, showing that the reaction time is less

Explosions

An explosion is a very fast reaction which releases a large volume of gaseous products. There is a danger of explosion in factories that handle powdered flammable substances. These substances include custard powder, flour and powdered sulfur.

Answer 2

In the absence of any other change, increasing surface area to volume ratio increases the rateof reaction.Explanation:Rates of reaction increase according to the frequency of collisions between the reacting species. If you have, for example, a solid reactant which is in contact with an aqueous solution of another, increasing the surface area to volume ratio, by grinding the solid into a finer powder, for example, means that the same number of moles of reactant now exist in a greater surface area form.This means that the surface of the reactant, where collissions take place and reactions occur, is greater, so there is scope for more collisions per mole to take place. Therefore the rate of reaction increases.