(a) 1 litre of a mixture of CO and CO₂ is taken. This mixture is passed through a tube containing red hot charcoal. The volume now becomes 1.6 litre. The volumes are measured under the same conditions. Find the composition of the mixture by volume.

(b) A compound contains 28 percent of nitrogen and 72 percent of metal by weight. 3 atoms of metal combine with 2 atoms of N. Find the atomic weight of metal.

The total number of electrons that take part in forming the bond in N₂ is

Which of the following is soluble in water?

Element X is strongly electropositive and element Y is strongly electronegative. Both are univalent. The compound formed would be