At 400 K, the root mean square (rms) speed of a gas X (molecular weight = 40) is equal to the most probable speed of gas Y at 60 K. The molecular weight of the gas Y is ___________.

The dissociation constant of a substituted benzoic acid at 25$$^\circ$$C is 1.0 $$\times$$ 10$$^{-4}$$. The pH of a 0.01 M solution of its sodium salt is __________.

The total number of $$\alpha$$ and $$\beta$$ particles emitted in the nuclear reaction $$_{92}^{238}U \to _{82}^{214}Pb$$ is _________.

The oxidation number of Mn in the product of alkaline oxidative fusion of MnO$$_2$$ is ___________.