Hydrogen and chlorine atoms react to form simple diatomic molecules in a 1:1 ratio, that is, HCl. The percent isotopic abundances of the chlorine isotopes are ³⁵Cl and ³⁷Cl are estimated to be 75.77% and 24.23%, respectively. The percent isotopic abundances of ²H and ³H are estimated to be 0.015% and less than 0.001%, respectively.

(a) How many different HCl molecules are possible, and what are their mass numbers (that is, the sum of the mass numbers of the H and Cl atoms)?

(b) Which is the most abundant of the possible HCl molecules? Which is the second most abundant?