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Science: Chemical Reaction and Equations: Balanced Chemical Equations

Any process that involves the rearrangement of structure of the substance or conversion of reactants into products is defined as Chemical Reaction.

Balanced Chemical Equations

mass of each element present in the products of a chemical reaction must be equal to its mass present in the reactants. In other words, the number of atoms of each element remains the same before and after a chemical reaction. In a balanced chemical equation number of atoms of a particular element present in the reactants and products must be equal.

Mg + O2 ⇾ 2MgO

Significance of Balanced Chemical Equations

  • the number of atoms and molecules taking part in the reaction and the corresponding masses in atomic mass unit .
  • the number of moles taking part in the reaction, with the corresponding masses in grams or in other convenient units.

relationship between the volume of the reactants and the products if all of them are in the gaseous state.

Steps to Form Balanced Equation

To show how to balance the equation, the following equation is used-

Fe + H2O ⇾ Fe3O4 + H2

Step 1: First of all, draw the boxes around each formula as shown below-

Fe + H2O ⇾ Fe3O4 + H2

Step 2: Find out the number of atoms of each element. For Example, on reactant side, 1 for Fe, 2 H, and 1 O and on product side we have, 3 for Fe, 4 for O and 2 for H.

Step 3: Start to balance the equation with the compound having maximum number of atoms. While balancing does not alter the formula of the compound.

Step 4: One by one balance each element on reactant and product side.

Fe + 4 H2O ⇾ Fe3O4 + H2 (partially balanced)

Step 5: After balancing number of atoms on both the side of the equation, finally check the correctness of the balanced equation.

3Fe + 4 H2O ⇾ Fe3O4 + 4 H2

Step 6: then write the symbols of the physical state of reactants and products as shown below-

3Fe (s) + 4 H2O (g) ⇾ Fe3O4 (s) + 4 H2 (g)

This above equation represents the balanced equation.

Types of Chemical Reaction

Combination Reactions

  • when two or more substances (elements or compounds) simply combine to form a new substance is called a Combination reaction.
  • For example, when a substance burns it combines with oxygen present in the air.

During burning it combines with oxygen as,

2Mg (s) + O2 (g) ⇾ 2MgO (s)

Now try the same with carbon.

C (s) + O2 (g) ⇾ CO2 (g)

Further, let us take a few activities.

Decomposition Reactions

Decomposition Reactions is type of reaction which involves breakdown of single reactant into simpler products. Decomposition of silver chloride into silver and chlorine in presence of sunlight is an example of decomposition reaction.

CaCO3 (s) heat CaO (s) + CO2 (g)

Limestone quick lime carbon dioxide

Displacement Reaction

The displacement reaction is one in which one element displaces another element from its compounds.

Zn (s) + CuSO4 (aq) ⇾ ZnSO4 (aq) + Cu (s)

Double Displacement Reactions

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

Na2SO4 (aq) + BaCl2 (aq) ⇾ BaSO4 (s) ↓ + 2NaCl (aq)

Sodiumbarium bariumsodium

Sulphate chloride sulphatechloride

(white ppt)

Oxidation and Reduction Reaction

In this Reaction , one reactant gets oxidized while the other gets reduced. Such reactions are called oxidation reduction reaction or Redox Reactions.

Example provides oxygen and therefore is an oxidizing agent and hydrogen takes this oxygen and therefore is a reducing agent. In a redox reaction, an oxidizing agent is reduced, and a reducing agent is oxidized.

Illustration: Oxidation and Reduction Reaction
  • Oxidation is loss of electrons
  • Reduction is gain of electrons
Illustration: Oxidation and Reduction Reaction

Corrosion

Corrosion is a destructive chemical process in which metals are oxidized in presence of air and moisture. The rusting of iron, tarnishing of silver, development of green coatings on copper, brass and bronze are a few examples of corrosion.

How Does One Prevent Corrosion?

  • Plating the metal (iron) with a thin layer of less easily oxidized metal like nickel or chromium. This plating keeps out air (oxygen) and moisture which are main causes of corrosion.
  • coating⟋connecting the metal with more reactive metal or with a metal which is more easily oxidized. For example, iron is connected to magnesium or coated with zinc for protecting it from corrosion. Iron rods are dipped in molten zinc to create a layer on their surface. This process of zinc coating over iron is called galvanization.
  • Applying a protective coating such as paint.
Illustration: How Does One Prevent Corrosion?

Rancidity

Oxidation of fats⟋oils results into the formation of acids. These acids give unpleasant smell and bad taste. This change is called rancidity. Many food items which are cooked⟋fried in oil⟋fat are kept in airtight containers for sale. Keeping food items in airtight containers helps to slow down the oxidation process.