Calculate the percentage composition of

(a) calcium chloride
(b) calcium nitrate

[Ca = 40 , Cl = 35.5 , N = 14 , O = 16]

Match the names of ions and radicals from 1 to 10 with their correct answer from A to Q.

Fill in the blanks with the correct word from the words in brackets :

1. A symbol represents a short form of a/an …………… [atom/element/molecule]
2. Compounds are always …………… [heterogeneous/homogeneous] in nature.
3. Variable valency is exhibited, since electrons are lost from an element from the …………… [valence/penultimate] shell.
4. A chemical equation is a shorthand form for a …………… [physical/chemical] change.
5. Relative molecular mass of an element/compound is the number of times one …………… of the substance is heavier than -1⁄12^th the mass of an atom of carbon [C¹²]. [atom/ion/molecule]

Underline the compound in each equation given below, which is incorrectly balanced and write the correct balancing for the same.

1. Na₂SO₃ + HCl ⟶ 2NaCl + H₂O + SO₂
2. CaC₂ + N₂ ⟶ 2CaCN₂ + C
3. Fe₂O₃ + 2H₂ ⟶ 2Fe + 3H₂O
4. Cl₂ + 2H₂O + SO₂ ⟶ 4HCl + H₂SO₄
5. 6NaOH + 3Cl₂ ⟶ 6NaCl + NaClO₃ + 3H₂O
6. C₂H₅OH + 3O₂ ⟶ 2CO₂ + 2H₂O
7. NaOH + CO₂ ⟶ Na₂CO₃ + H₂O
8. 2H₂O + 2Cl₂ ⟶ 2HCl + O₂
9. 3CuO + NH₃ ⟶ 3Cu + 3H₂O + N₂
10. PbO₂ + 4HCl ⟶ PbCl₂ + H₂O + Cl₂