Experimentally it was found that a metal oxide has formula M_0.98O. Metal M, present as M²⁺ and M³⁺ in its oxide. Fraction of the metal which exists as M³⁺ would be

A gaseous hydrocarbon gives upon combustion 0.72 g of water and 3.08 g of CO₂. The empirical formula of the hydrocarbon is

Consider the following reaction:

$$xMnO_4^- + yC_2O_4^{2-}$$ + zH⁺ $$\to$$ xMn²⁺ + 2yCO₂ + $${z \over 2}{H_2}O$$

The value's of x, y and z in the reaction are, respectively :

Let A and B be two sets containing 2 elements and 4 elements respectively. The number of subsets of A $$ \times $$ B having 3 or more elements is :