gcse chemistry higher - rate of reaction

rate of a chemical reaction of reactants?

How quickly the reactants in a reaction are used up

rate of a chemical reaction of products?

How quickly the products in a reaction are formed

formula for a mean rate of reaction in terms of reactants/products?

= change in quantity of reactant or product used or formed ÷ time taken

How can you measure the quantity of a reactant or product?

in grams or cm3

What are the two possible units for rate of reaction?

g/s or cm3/s

How could you measure the rate of a reaction from a graph?

Draw a tangent to the curve and calculate the gradient (change in y ÷ change in x).

What is "collision theory"?

The theory that chemical reactions only occur when particles collide with sufficient energy . - rate depends on the frequency of successful collisions.

What factors can affect the rate of a reaction?

• Temperature,

• increased surface area

• increased concentration or reactants in solution

• pressure of gases

• use of catalyst

State the effect of increasing the SURFACE AREA on the rate of a reaction

Increases the rate of reaction

Explain why increasing the SURFACE AREA increases the rate of a reaction

More particles are available to collide, there are therefore more frequent collisions between reactants.

State the effect of increasing the CONCENTRATION on the rate of reaction

Increases rate of reaction

Explain why increasing the CONCENTRATION increases the rate of reaction

More concentrated means more particles in solution, therefore more frequent collisions between reactants.

State the effect on increasing the PRESSURE OF A GAS on the rate of reaction

Increases rate of reaction

Explain why increasing the PRESSURE OF A GAS increases the rate of a reaction

Less space for the particles to move around in, therefore more frequent collisions

State the effect of increasing the TEMPERATURE on the rate of reaction

Increases rate of reaction

Explain why increasing the TEMPERATURE increases the rate of reaction

Increases the speed at which particles move therefore more frequent collisions. Increases the number of particles which have the activation energy therefore more collisions result in a reaction.

What is the activation energy?

The minimum amount of energy particles need before they will be able to react when it collides with another particle

What is a catalyst?

Something which changes the rate of a reaction but is not used up in that reaction

How do catalysts speed up reactions?

They provide another route for the reaction to take place which has a lower activation energy.

Pros of catalyst