FORMULAE & EQUATIONS

• Meaning of an equation, if we consider the following equation:

Zn_(s)  +  H₂SO_4(aq)       →  Zn SO_4(aq)  +  H_2(g)

65          (2 + 32 + 64)     (65 + 32 + 64)

65               98             →   161g +   2

It expresses the following information:

• That 1 molecule of H₂SO₄ contains:  2 atoms of H, 1 atom of S, and 4 atoms of oxygen.
• A molecule of ZnSO₄ contains 1 atom of Zn, 1 atom of sulphur and 4 atoms of oxygen.

 CHEMICAL EQUATIONS

A chemical equation:

Is the symbols and formulae which represent a chemical reaction

e.g. C(s)   +   O₂(g) → CO₂(g)

2H₂(g)   +   O₂(g)  →   2H₂O(l)

Laws governing writing chemical equation.

1.         The reactants are written on the left-hand side and the products on the right-hand side.

2.         The number atoms of the products must balance with those of the reactants.

3.         Each element or compound must have a state symbol.

Balancing the equation

Zn(s)   +   2HCl(aq)  →   ZnCl₂(aq)  +  H₂(g)

Zn        =          1                                                          Zn        =          1

H         =          2                                                          H         =          2

Cl        =          2                                                          Cl        =          2

Also, watch this

EXERCISE

Balance the following equations.

1.         C₄H₈  +  O₂  →         H₂O  +  CO₂

2.         P   +  O₂  →   PO₅

3.         Cu(NO₃)₂   +   NaCl →  NaNO₃   +  CuCl₂

4.         NO   +   O₂  →   NO₂

5.         KCl  →   K   +   Cl₂

6.         Cu   +   H₂SO₄   →  CuSO₄   +  H₂O   +  SO₂

7.         CO₂   +   H₂O  →   C₆H₁₂O₆   +   O₂

8.         Cu   +  HNO₃   →   Cu(NO₃)₂   +   NO₂   +   H₂O

9.         NH₃   +    O₂  →   NO   +   H₂O

10.       P₄O₁₀   +   CaO   →   Ca₃(PO₄)₂

11.       FeSO₄   +   O₂   +   H₂O   →   Fe(OH) SO₄

12.       P   +   Fe₂O₃  →   P₄O₁₀   +  Fe

13.       Zn(OH)₂  +  HNO₃  → Zn(NO₃)₂  +  H₂O

14.       NH₄OH  +  H₃PO₄ →  (NH₄)₃PO₄  +  H₂O

15.       Indicate whether the equations are balanced as written:

• 2Sn  +  2H₂SO₄  →  2SnSO₄  +  SO₂  +  2H₂O
• 3Cl₂  +  6NaOH →  5NaCl  +  NaClO₃  +  3H₂O

Answers

 1.        C₄H₈  +  6O₂  →      4H₂O  +4 CO₂

2.         2P   +5 O₂  →  2 PO₅

3.         Cu(NO₃)₂   +  2 NaCl →  2NaNO₃   +  CuCl₂

4.         2NO   +   O₂  →   2NO₂

5.         2KCl  →   2K   +   Cl₂

6.         Cu   +   2H₂SO₄   →  CuSO₄   +  2H₂O   +  SO₂

7.         6CO₂   +   6H₂O  →   C₆H₁₂O₆   +   6O₂

8.         Cu   +  4HNO₃   →   Cu(NO₃)₂   +   4NO₂   +   2H₂O

9.         4NH₃   +    3O₂  →   4NO   +   2H₂O

10.       P₄O₁₀   +   6CaO   →   2Ca₃(PO₄)₂

11.       4FeSO₄   +   2O₂   +   2H₂O   →   4Fe(OH)SO₄

12.       4P   +   10Fe₂O₃  →   P₄O₁₀   +  20Fe

13.       Zn(OH)₂  +  2HNO₃  →Zn(NO₃)₂  +  2H₂O

14.       3NH₄OH + H₃PO₄ →  (NH₄)₃PO₄ + 3H₂O

15.       Indicate whether the equations are balanced as written:

• 2Sn + 2H₂SO₄  →  2SnSO₄ +  SO₂  +  2H₂O (not balanced)
• 3Cl₂ + 6NaOH →  5NaCl +  NaClO₃  +  3H₂O (balanced)

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