16. Balance the following equations
(i) H₂O₂ -> H₂O + O₂
(ii) S + O₂ -> SO₃
(iii) C₂H₂ + O₂ -> CO + H₂O
(iv) MnO₂ + HCl -> MnCl₂ + Cl₂ + H₂O

17. Classify the following molecules as mono, di, tri, tetra, penta and hexatomic molecules.
H₂, P₄, SF₄, SO₂, PC_l3, C₂H₂, CH₃OH, PC_l5, H₂O₂, HCl, Cl₂O

18. What is meant by molecular formula? Hydrogen peroxide has the molecular formula H₂O₂. What mass of oxygen can be formed from 17 g of H₂O₂ if decomposition of H₂O₂ takes place.

19. Write ‘true’ or ‘false’.
A balanced chemical equation shows
(i) the formulas of the products
(ii) the molar proportions in which the products are formed
(iii) that a reaction can occur
(iv) the relative number of atoms and molecules which react
(v) that a reaction is exothermic

20. What is the mass of
(i) 6.02 × 10²³ atoms of O
(ii) 6.02 × 10²³ atoms of P
(iii) 6.02 × 10²³ molecules of P₄
(iv) 6.02 × 10²³ molecules of O₂

21. How many atoms are there in
(i) two moles of iron
(ii) 0.1 mol of sulphur
(iii) 18 g of water, H₂O
(iv) 0.44 g of carbon dioxide, CO₂

22. Define the following
(i) Law of constant proportions
(ii) Law of multiple proportions
(iii) Avogadro’s Law
(iv) Gay Lussacis Law
(v) Dalton’s atomic theory

23. Convert into mole
(i) 12 g of oxygen gas (O₂)
(ii) 20 g of water (H₂O)
(iii) 22 g pf carbon dioxide (CO₂)