Chemistry - Chapter 1: Chemical Reactions and Equations

Displacement Reaction

Displacement Reaction

A reaction in which the more reactive metal displaces the less reactive metal from its compound in solution or in molten forn

Iron and Copper Sulphate Reaction

Fe + CuSO4 —— FeSO4 + Cu

CuSO4 - blue

FeSO4 - green

Zinc and Copper Sulphate Reaction

Zn + CuSO4 —— ZnSO4 + Cu

ZnSO4 - colourless

Lead and Copper Chloride Reaction

Pb + CuCl2 —— PbCl2 + Cu

PbCl2 - colourless

Double Displacement Reaction

Reactions in which there is an exchange of ions between the reactants are called double displacement reaction.

Precipitation Reaction

Any reaction that produces a precipitate

Sodium Sulphate and Barium Chloride Reaction

Na2SO4 + BaCl2 —— BaSO4 + 2NaCl

All colourless except BaSO4 (white precipitate)

Lead Nitrate and Potassium Iodide Reaction

Pb(NO3)2 + 2KI —— 2KNO3 + PBI2

Pb(NO3)2, KI - white

KNO3 - white/grey

PbI2 - yellow precipitate

Oxidation

If a substance gains oxygen or loses hydrogen during a reaction, it is said to be oxidised

Reduction

If a substance loses oxygen or gains hydrogen during a reaction, it is said to be reduced.

Redox Reaction

During a reaction, if one reactant gets oxidised while the other gets reduced it is called a redox reaction.

Oxidisation of Copper to Copper Oxide

2Cu + O2 —— 2CuO

Cu - brown

Copper Oxide and Hydrogen Reaction (Redox Reaction)

Zinc Oxide and Carbon Reaction

ZnO + C —— Zn + CO

Oxidising agent - ZnO

Reducing agent - C

Manganese Oxide and Hydrochloric Acid Reaction

MnO2 + 4HCl —— MnCl2 + 2H2O + Cl2

Oxidising agent - MnO2

Reducing agent - HCl

Corrosion

When a metal is attacked by substances around it such as moisture, acid, etc. it is said to corrode and this process is known as corrosion.

Eg - black coating on silver
- green coating on copper
- brown coating on iron

Rancidity

Oxidation of fats and oil in food materials resulting in a bad smell or taste

Rusting of Iron

Iron, in the presence of moisture, reacts with oxygen to form hydrated iron oxide (brown coating). This is known as the rusting of iron.

Preventing Rancidity

• Keep food in air-tight containers

• Refrigeration

• Add antioxidants to foods containing fats and oil

• Oil and fat containing food items are flushed with nitrogen

Antioxidant

Substance that prevents oxidisation

Chemical Reaction

Whenever a chemical change occurs, we can say that a chemical change occurs

Magnesium and Oxygen Reaction

2Mg + O2 —— 2MgO

Observations in a Chemical Reaction

• Change in state

• Change in colour

• Evolution of gas

• Change in temperature

Reactants and Products

The substances that undergo chemical change in a reaction are the reactants.

The new substance formed during the reaction is the product.

Unbalanced Equation

The equation is unbalanced when the mass is not the same on both sides of the equation. It is also known as a skeletal chemical equation.

Law of Conservation of Mass

The total mass of the elements present in the products of a chemical reaction has to be equal to the total mass of the elements present in the reactants.

Zinc and Sulphuric Acid Reaction

Zn + H2SO4 —— ZnSO4 + H2

Balanced Chemical Equation

If the number of atoms is the same on both sides of the arrow, it is a balanced chemical equation.

Iron and Water Vapour Reaction

3Fe + 4H2O(g) —— Fe3O4 + 4H2(g)

Carbon Monoxide and Hydrogen Reaction

CO + 2H2 —— CH3OH

CH3OH - Methanol

Photosynthesis

6CO2 + 12H2O —— C6H12O6 + 6O2 + 6H2O