A mixture of 0.1 mol of a weak acid HX and 0.2 mol of another weak acid HY is dissolved in 1 kg of water. The degrees of ionization of the two acids HX and HY in the final solution are 0.1 and 0.2 , respectively. Assuming Rault's law to be valid, the elevation of boiling point ( T_b ) , in terms of the boiling point elevation constant (K_b ) , is given by