Rate- Concentration Graphs:

Zero Order: Straight horizontal line with zero gradient. Rate = k[A]0 so rate =

k = Y intercept. Reaction rate does not change with concentration. Can confirm first order of

reaction of graph by calculating two half-lives and constant. Therefore no change to half- life if

initial concentration increased.

First Order: Straight line through origin. Rate = k[A]1 so rate = k[A].. Rate constant determined

from gradient of line.

Second Order: Increasing gradient curve starting at origin. Rate = [A]2

. Have to plot second graph

of rate against concentration squared. Will get straight line through origin. Rate constant

determined from gradient of this line.

Finding Initial Rate of Formation: Balancing number of substance forming x rate.

Initial Rate: Initial rate can be found by drawing tangent at t = 0.

Clock Reaction: Clock reaction can obtain initial rate. The time is measured for colour change or

precipitate to appear.

Average Rate: Assumed that average rate of reaction over this time will be same as initial rate.

The shorter the time measured, less the rate changes over that time and closer to initial rate.

Initial rate is proportional to 1/ t. Clock reaction repeated with different concentration and 1/ t

calculated for each. Vary concentration of one reactant whilst keeping concentration of other

reactants constant. Plot rate against concentration to determine order.

Use 1/t when finding initial rate.

Iodine Clocks: Starch added to make iodine formed turn blue- black colour. Aqueous iodine is

orange- brown. Aqueous sodium thiosulfate removes the iodine first formed to delay. Solution

colourless at start.

Methods to Measure Rate of Reaction: Mass change with scales e.g. If gas escapes. Gas Syringe/

Measuring cylinder to measure the volume of gas produced. Colorimeter to measure the change

in colour intensity or amount of precipitate formed.