Question

Calculate the mass of 0.00456 moles of (NH4)2SO4

Answer 1

To find the mass you need to find the weight of a mol of the molecules by adding up the atomic mass.

N =  14.007 g/mol
H = 1.008 g/mol
S = 32.065 g/mol
O = 16 g/mol

2(14.007) + 8(1.008) + 32.065 + 4(16) = 132.143 g/mol

Now you know how much an entire mol weight you multiply it by how much you actually have 

0.00456 * 132.143 = 0.603 g