Why are the masses of some elements listed as whole numbers in parentheses?

Can someone me with these questions plz.

How many moles of potassium hydroxide are needed to completely react with 2.94 moles of aluminum sulfate

The solid xy decomposes into gaseous x and y: xy(s) m x(g) + y(g) kp = 4.1 (at 0 °c) if the reaction is carried out in a 22.4 l container, which initial amounts of x and y will result in the formation of solid xy?