Balancing Chemical Equations at a glance

BALANCING CHEMICAL EQUATIONS

Chemical equations are representations of chemical reactions using  symbols and formulae of the elements and compounds involved. When writing chemical equations, the reactants are always written on the left hand (LHS) side while the products are written on the right hand(RHS) side. For example, if A and B combine together to give C and D, the equation of the reaction is written as:

    A + B   →    C + D
      Reactants               Products

 

Balancing Chemical Equation 

All chemical equations must be balanced so that the law of conservation of mass matter will be obeyed 

We balance equations by putting coefficients (positive integers) in front of the formulars only. 

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Example 1: Write a balanced equation for the combustion of magnesium in oxygen 

Solution:

Step I: Write the reactants and predict the products

   Mg(s) + O2(g) → MgO(s) 

The equation is not balanced and so to balance it, we will place coefficients in front of each molecule to balance the number of atoms. Thus, the balanced equation is:

  2MgO(s)+ O2(g) → 2MgO

 

Example 2: Write a balanced equation for the combustion of ethane in oxygen.

Solution:

    C2H6 +  O2 →2CO2 + 3H2O

The equation is balanced. However, equations are written with whole number coefficients. By multiplying the entire equation by 2, we get

  2C2H6 + 7O2 →4CO2 + 6H2O

Informations supplied by a balanced equation

1.    The reactants and the products they form.

2.     It tells us the physical states of the reactants and products. Whether solid liquid gaseous or aqueous 

3.     It tells if a reaction is reversible or not reversible.

4.     It gives us the stoichiometry of the reaction (i.e. the relationship between the number of mole of reactants and products) in terms of mole ratio

 Consider the table below:

Equation	Mole ratio/ Mass ratio
2HCl + MgCO3→ MgCl2 + H2O + CO2	2 moles of HCl and 1 mole of MgCO3produced 1 mole of MgCl2, 1 mole of H2Oand 1 moles of CO2
2HCl + MgCO3 → MgCl2 + H2O + CO2	73g of HCl and 84g of MgCO3produced 95g of MgCl2, 18g of H2Oand 44g of CO2

Objective Questions 

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