What is A and what is b also on c

How many moles of magnesium is 3.01 x10^22 atoms of magnesium?

The boiling point of propanoic acid is higher than that of 1-butanol because: propanoic acid has a higher molecular weight than 1-butanol. propanoic acid is more soluble in water than 1-butanol. propanoic acid is a better hydrogen bond donor than 1-butanol. propanoic acid forms hydrogen bonded dimers and 1-butanol does not. 1-butanol forms hydrogen bonded dimers and propanoic acid does not.

In 2002, the rare earth elements mine in mountain pass, california was closed because