What mass of chloral hydrate (C2H3Cl3O2) would contain 1.0 grams of chlorine?

Answer 1

Do you want 1 g Cl2 or 1 g of the Cl atom?
I expect you want 1 g chlorine atom (not Cl2).
moles Cl = 1/atomic mass Cl = 1/35.5 = 0.0282 moles Cl.

Since chloral hydrate contains 3 Cl atoms/mole of the hydrate you will want 1/3 x (0.0282) = ?? moles hydrate.
g hydrate = moles hydrate x molar mass hydrate.
If I have interpreted the problem the wrong way, just adjust the numbers above to fit.