Which of the following binary mixtures will have same composition in liquid and vapour phase?

Binary mixtures that have the same composition in liquid and vapour phase are known as azeotropes. These solutions boil at a constant temperature. The two types of azeotropes are minimum boiling azeotropes and maximum boiling azeotropes. Water-nitric acid is a maximum boiling azeotrope and water-ethanol is a minimum boiling azeotrope. The options (i) and (iv) are examples of ideal solutions, hence they cannot be azeotropes.

Hence the correct answers are (ii) and (iii).