Photochemical Reactions

Photosynthesis – the conversion of water and carbon dioxide into glucose and oxygen for energy. The glucose produced is used to make sugars and starch as carbohydrates.

Carbon Dioxide + Water -> Glucose + Oxygen Gas

6 CO2          + 6 H2O  -> C6H12O6 +  6 O2

Respiration – reverse of photosynthesis; combustion reaction

Glucose + Oxygen Gas -> Carbon Dioxide + Water

C6H12O6   +         6 O2            ->        6 CO2                +   6 H2O

Photography – this photochemical reaction is used as the basis of black and white photography. The photographic film is made of flexible plastic, coated with a layer of gelatine with millions of particles of silver bromide spread through it which is changed to silver when light falls on the exposed parts of the film.

Silver Bromide -> Silver + Bromide

2AgBr          ->   2Ag  +   Br2

Hydrogen as a fuel:

• Hydrogen is considered to be the fuel of the future and is being trialled by motor manufacturers as an alternative to fossil fuels such as
• Hydrogen is non toxic, produces more energy per gram than any other fuel and burns cleanly to form water so there is no exhaust pollution. It has a lower flammability than fossil
• Hydrogen is obtained from the electrolysis of water which is plentiful. So far this is not a cost efficient alternative to using fossil fuels and non-renewable if produced using fossil fuels or nuclear
• Hydrogen is difficult to transport and store. Because it is too light to liquefy easily, a large fuel tank would be
• It is explosive in correct proportions with