Note on Balancing Chemical Equation

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Word equation:

The chemical reaction which is expressed in terms of the word (name of reactants and products) is called word equation. For example:

Sodium + Chlorine $$\longrightarrow$$ Sodium Chloride

Formula equation:

The chemical equation which is written in terms of symbols by writing their molecular formula is called formula equation. It is of two types:

1. Skeletal equation: The formula equation in which the number of ions, radicals, atoms etc. in reactant and product side is not equal then it is called skeletal equation. It is also sometimes called unbalanced equation.

The above equation is skeletal equation as the number of one oxygen atom in reactant and product sides are not equal.
2. Balanced equation: The formula equation is which the number of atoms, radicals, ions, etc is made equal in both reactant and product side is called balanced equation. For example:

Above equation is now a balanced equation because the number of oxygen is made equal in both reactant and product by keeping suitable number.

Balancing a chemical equation

An unbalanced chemical equation can be converted into a balanced equation by using following steps:

Step 1: Write the word equation.

Potassium chlorate $$\overset{Heat}{\longrightarrow}$$ Potassium chloride + oxygen

Step 2: Convert the word equation into formula equation.

KClO3$$\overset{\Delta}{\longrightarrow}$$KCl +O2

Step 3: Count the number of atoms, ions, etc of the reactant and product and make them equal by using the suitable number in front of them.

2KClO3 $$\overset{\Delta}{\longrightarrow}$$ 2KCl +3O2

Information conveyed by balanced chemical equations

• It gives symbols, name and the molecular formula of the chemical substances involved as reactants and products.
• It gives the relative number of atoms and molecules of reactants that take part in the chemical reaction.
• It gives the relative number of atoms and molecules of products formed in the reaction.
• It gives the ratio of masses of reactants and products.
• It shows the type of chemical reaction.

Limitations of balanced chemical equations

• The physical states of reactants and products is not known.
• The concentration of reactants and products in the end, is not known.
• The rate of chemical reaction and the time taken for its completion is not known.
• The conditions under which chemical reaction takes place is not known.
• Whether the heat is released or absorbed during the reaction is not known.
• Some reactions may be explosive. It is not revealed by the chemical equation.
• Whether the reaction is reversible or not.

• The chemical reaction which is expressed in terms of word (name of reactants and products) is called word equation.
• The chemical equation which is written in terms of symbols by writing their molecular formula is called formula equation.
• The formula equation in which the number of ions, radicals, atoms etc. in reactant and product side is not equal then it is called skeletal equation.
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Very Short Questions

The skeletal equation of the given word equation is given below,

Word equation: Potassium + Oxygen → Potassium oxide
Skeleton equation: K + O2  → K2O
Balanced equation: 4K + O2 → 2K2O

The skeletal equation of the given word equation is given below,

Word equation: Nitrogen + Oxygen $$\overset{3000^oC}{\longrightarrow}$$ Nitric Oxide
Skeleton equation: N2 + O2 → NO
Balanced equation: N2 + O2 → 2NO

The skeletal equation of given world equation is given below,

Word Equation: Ethane + Oxygen $$\overset{heat}{\longrightarrow}$$ Carbon dioxide + Water
Skeleton Equation: C6H6 + O2  $$\overset{\Delta}{\longrightarrow}$$ CO2 + H2
Balanced Equation:  2C6H6 + 7O2  $$\overset{\Delta}{\longrightarrow}$$ 4CO2 + 6H2

The skeletal equation of given world equation is given below,

Word Equation: Silver nitrate + Sodium chloride → Silver chloride + Sodium nitrate
Skeleton Equation: AgNO3  + NaCl → AgCl + NaNO3
Balanced Equation:  AgNO3  + NaCl → AgCl + NaNO3

The skeletal equation of given world equation is given below,

Word Equation: Zinc + Hydrochloric acid →Zinc chloride + Hydrogen
Skeleton Equation: Zn(s) +  HCl(aq) → ZnCl2(aq) + H2(g)
Balanced Equation:  Zn(s) +  2HCl(aq) → ZnCl2(aq) + H2(g)

The skeletal equation of the given word equation is given below,

Word equation: Calcium carbonate  $$\overset{\Delta}{\longrightarrow}$$ Calcium oxide + Carbon dioxide
Skeleton equation: CaCO3  $$\overset{\Delta}{\longrightarrow}$$ CaO + CO2
Balanced equation: CaCO3  $$\overset{\Delta}{\longrightarrow}$$ CaO + CO2

The skeletal equation of the given word equation is given below,

Word equation:  Copper nitrate + Nitrogen dioxide + water.
Skeleton equation: Cu + HNO3 → Cu(NO3)2 + NO2 + H2O
Balanced equation: Cu + 4HNO3 → Cu(NO3)2 + 2NO2 + 2H2O

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• The chemical reaction which is expressed in terms of the word (name of reactants and products) is called

Sentence Equation
Formula Equation
Balanced Equation
Word Equation
• What is the balanced chemical equation for Na + Cl2 → NaCl?

3Na + Cl2 → 3NaCl
Na + Cl2 → NaCl
2Na + Cl2 → 2NaCl
3Na + Cl2 → 2NaCl
• What is the balanced chemical equation for NH4Cl + Ca(OH)2 →  CaCl2 + NH3 + H2O ?

2NH4Cl + Ca(OH)2 →  CaCl2 + 2NH3 + 2H2O
2NH4Cl + Ca(OH)2 →  2CaCl2 + NH3 + 2H2O
3NH4Cl + Ca(OH)2 →  2CaCl2 + 3NH3 + H2O
NH4Cl + 2Ca(OH)2 →  CaCl2 + NH3 + 2H2O
• What is the balanced chemical equation for Zn(s) + HCl(aq) → ZnCl2(aq) + H2(g) ?

Zn(s) + 4HCl(aq) → 2ZnCl2(aq) + H2(g)
Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g)
2Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g)
2Zn(s) + 3HCl(aq) → 2ZnCl2(aq) + 1H2(g)
• What is the balanced chemical equation for CaCO3  ( overset{heat}{longrightarrow})  CaO + CO2↑ ?

CaCO3  ( overset{heat}{longrightarrow})  CaO + CO2
2CaCO3  ( overset{heat}{longrightarrow})  CaO + 2CO2
2CaCO3  ( overset{heat}{longrightarrow})  2CaO + CO2
3CaCO3  ( overset{heat}{longrightarrow})  2CaO + 2CO2
• What is the balanced chemical equation for Cu + HNO3 → Cu(NO3)2 + NO2 + H2O?

2Cu + 2HNO3 → 2Cu(NO3)2 + 2NO2 + 2H2O
2Cu + 4HNO3 → 2Cu(NO3)2 + NO2 + 2H2O
2Cu + 2HNO3 → 2Cu(NO3)2 + 2NO2 + H2O
Cu + 4HNO3 → Cu(NO3)2 + 2NO2 + 2H2O
• The chemical equation which is written in terms of symbols and molecular formulae is called

Symbolic equation
Formula equation
Molecular equation
Word equation
• What is the balanced chemical equation for H2 + O2 → H2O ?

2H2 + O2 → 2H2O
2H2 + O2 → 3H2O
6H2 + 3O2 → 6H2O
H2 + 2O2 → 2H2O
• What is the balanced chemical equation for Na + H2O → NaOH + H2 ?

2Na + 2H2O → 2NaOH + H2
4Na + H2O → 4NaOH + H2
Na + 2H2O → 2NaOH + 2H2
2Na + H2O → 2NaOH + 2H2