How many atoms of each type are represented in each of the following? f. 5Fe(No3)2 g. 4Mg3(PO4)2 h. 2(NH4)2SO4

Answer 1

You need to know the following rules.
1. Subscripts (the 3 in NO3 in f) multiply the preceding atom while the 2 in (NO3)2 multiply everything inside the parentheses. So you have 2 N atoms and 6 O atoms in f (so far--since this doesn't count the 5 coefficient).

2. Coefficients such as the 5 in f multiply everything that follows.

Therefore, you have 5 Fe atoms, 2*5 = 10 N atoms and 2*3*5 = 30 O atoms in f.

For 4Mg3(PO4)2 you have 12 Mg, 8 P and 32 O atoms.