$$0.63 \mathrm{~g}$$ of oxalic acid is dissolved in order to obtain $$250 \mathrm{~cm}^3$$ of its solution. Find the normality of this solution. [oxalic acid $$\left.(\mathrm{COOH})_2 \cdot 2 \mathrm{H}_2 \mathrm{O}\right]$$

$$7.8 \mathrm{~g}$$ of a compound having molecular formula $$\mathrm{C}_6 \mathrm{H}_6$$, on reacting with $$\mathrm{CH}_3 \mathrm{COCl} / \mathrm{AlCl}_3$$ gives $$8.4 \mathrm{~g}$$ of a product which has molecular formula $$\mathrm{C}_8 \mathrm{H}_8 \mathrm{O}$$. Calculate the percentage yield of the product $$\mathrm{C}_8 \mathrm{H}_8 \mathrm{O}$$. (Given, atomic weights of $$\mathrm{H}, \mathrm{C}$$ and $$\mathrm{O}$$ respectively are 1, 12 and 16)

The complete combustion of one mole of benzene produces .......... grams of carbon dioxide.

An alloy of metals X and Y weighs 12 g and contains atoms X and Y in the ratio of 2 : 5. The percentage of metal X in the alloy is 20 by mass. If the atomic mass of X is 40 amu what is the atomic mass of metal Y ?