Berapa mol 4gram Ca(OH)2. (Ar. CA=40 O=16 H=1)

Mr Ca(OH)2 = (1 x Ar Ca) + (2 x Ar O) + (2 x Ar H) = (1 x 40) + (2 x 16) + (2 x 1) = 74

Mol = massa zat/Mr zat
= 4/74
=0.05 mol