CHEMISTRY
CHEMICAL REACTIONS AND EQUATIONS
- Magnesium ribbon burns with a dazzling white flame and changes
into a white powder, called magnesium oxide. Magnesium oxide is
formed due to the reaction between magnesium and oxygen.
▫ 2Mg + O2 => 2MgO
- We can determine if a chemical reaction has taken place if :-
1. There is change is colour.
2. Change in state.
3. Change is temperature.
4. Evolution of gas.
- Zinc + sulphuric acid => zinc sulphate + hydrogen
▫ Zn + H2So4 => ZnSo4 + H2
- Iron + water => Iron oxide + hydrogen
▫ 3Fe + 4H2O => Fe3O4 + 4H2
- There are 3 types of chemical reactions :-
1. Combination reaction
- A reaction in which a single product is formed from 2 or more
reactants is called combination reaction.
- Calcium oxide (quick lime) reacts with water to form calcium
hydroxide (slaked lime) and releases heat in the process.
- Calcium oxide + water => calcium hydroxide + heat
▫ CaO + H2O => Ca(OH)2 + heat
- Calcium hydroxide (slaked lime) is also used for white washing
walls. Calcium hydroxide reacts with carbon dioxide from the air
and forms a thin layer calcium carbonate on the walls.
, - Calcium hydroxide + carbon dioxide => calcium carbonate + water
▫ Ca(OH)2 + CO2 => CaCO3 + H2O
- Reactions in which heat is released along with the formation of
products is are called Exothermic reactions.
- Fun fact : Respiration is an exothermic reaction.
- Decomposition of vegetable matter into compost is also and
exothermic reaction.
2. Decomposition reaction
- In this reaction a single reactant breaks down to form simpler
products.
- Ferrous sulphate crystals on heating loses water and the colour of
the crystal changes. Then it decomposes to ferric oxide, sulphur
dioxide and sulphur trioxide.
- Ferrous sulphate = heat > ferric oxide + sulphur dioxide + sulphur
trioxide
▫ 2Fe(SO)4 = heat > Fe2O3 + SO2 + SO3
- Calcium oxide (quick lime) has many uses, one is in the
manufacture of cement.
- When a decomposition reaction is carried out by heating, it is called
Thermal decomposition.
- Chemical formula for marble is CaCO3 (calcium carbonate).
- Calcium carbonate = heat > calcium oxide + carbon dioxide
▫ CaCO3 = heat > CaO + CO2
- Lead nitrate when heated released brown coloured fumes/gas.
These fumes are nitrogen dioxide.
- Lead nitrate = heat > lead oxide + nitrogen dioxide + oxygen
▫ 2Pb(NO3)2 = heat > 2 PbO + 4NO2 + O2
CHEMICAL REACTIONS AND EQUATIONS
- Magnesium ribbon burns with a dazzling white flame and changes
into a white powder, called magnesium oxide. Magnesium oxide is
formed due to the reaction between magnesium and oxygen.
▫ 2Mg + O2 => 2MgO
- We can determine if a chemical reaction has taken place if :-
1. There is change is colour.
2. Change in state.
3. Change is temperature.
4. Evolution of gas.
- Zinc + sulphuric acid => zinc sulphate + hydrogen
▫ Zn + H2So4 => ZnSo4 + H2
- Iron + water => Iron oxide + hydrogen
▫ 3Fe + 4H2O => Fe3O4 + 4H2
- There are 3 types of chemical reactions :-
1. Combination reaction
- A reaction in which a single product is formed from 2 or more
reactants is called combination reaction.
- Calcium oxide (quick lime) reacts with water to form calcium
hydroxide (slaked lime) and releases heat in the process.
- Calcium oxide + water => calcium hydroxide + heat
▫ CaO + H2O => Ca(OH)2 + heat
- Calcium hydroxide (slaked lime) is also used for white washing
walls. Calcium hydroxide reacts with carbon dioxide from the air
and forms a thin layer calcium carbonate on the walls.
, - Calcium hydroxide + carbon dioxide => calcium carbonate + water
▫ Ca(OH)2 + CO2 => CaCO3 + H2O
- Reactions in which heat is released along with the formation of
products is are called Exothermic reactions.
- Fun fact : Respiration is an exothermic reaction.
- Decomposition of vegetable matter into compost is also and
exothermic reaction.
2. Decomposition reaction
- In this reaction a single reactant breaks down to form simpler
products.
- Ferrous sulphate crystals on heating loses water and the colour of
the crystal changes. Then it decomposes to ferric oxide, sulphur
dioxide and sulphur trioxide.
- Ferrous sulphate = heat > ferric oxide + sulphur dioxide + sulphur
trioxide
▫ 2Fe(SO)4 = heat > Fe2O3 + SO2 + SO3
- Calcium oxide (quick lime) has many uses, one is in the
manufacture of cement.
- When a decomposition reaction is carried out by heating, it is called
Thermal decomposition.
- Chemical formula for marble is CaCO3 (calcium carbonate).
- Calcium carbonate = heat > calcium oxide + carbon dioxide
▫ CaCO3 = heat > CaO + CO2
- Lead nitrate when heated released brown coloured fumes/gas.
These fumes are nitrogen dioxide.
- Lead nitrate = heat > lead oxide + nitrogen dioxide + oxygen
▫ 2Pb(NO3)2 = heat > 2 PbO + 4NO2 + O2
