Revision notes topic questions past papers

CIE IGCSE Chemistry Resources

REVISION NOTES      TOPIC QUESTIONS      PAST PAPERS

EXAM TIP

When answering questions on the effect of concentration on the rate of reaction, you 

should mention that there are more particles per unit volume (usually cm

3

) and this 

causes an increase in the rate of collisions.

EXTENDED ONLY 

Photochemistry

Photochemical reactions

•  These reactions occur only when light is present

•  The greater the intensity of ultraviolet light then the greater the rate of reaction

•  E.g. the substitution of hydrogen atoms in methane by chlorine:

CH

4

  +  Cl

2

 

→  CH

3

Cl  +  HCl

Silver salts in photography

•  Black and white photography film surfaces contain crystals of silver bromide

•  When exposed to light they decompose to silver: