The diffusion coefficient of an ideal gas is proportional to its mean free path and mean speed. The absolute temperature of an ideal gas is increased 4 times and its pressure is increased 2 times. As a result, the diffusion coefficient of this gas increases x times. The value of x is ___________:

The compound(s) with TWO lone pairs of electrons on the central atom is(are)

P is the probability of finding the 1s electron of hydrogen atom in a spherical shell of infinitesimal thickness, dr, at a distance r from the nucleus. The volume of this shell is $$4\pi r^2dr$$. The quantitative ketch of the dependence of P on r is

The product(s) of the following reaction sequence is (are)