Mohr’s Salt is a common laboratory reagent. Use the information of the most abundant
isotopes below to calculate the formula mass, Mr , of the hydrated salt.
Formula of Mohr’s Salt: (NH4)2Fe(SO4)2.6H2O
Most abundant isotopes: ,H, N, O, S, Fe

Answer:

10) F

This is a simple addition question.

No. of N = 2
Mass number of N = 14
Total mass of N = (14 x 2) = 28

No. of H = 20
Mass number of H = 1
Total mass of H = (20 x 1) = 20

No. of Fe = 1
Mass number of Fe = 56
Total mass of Fe = (56 x 1) = 56

No. of S = 2
Mass number of S = 32
Total mass of nitrogen = (32 x 2) = 64

No. of O = 14
Mass number of O = 16
Total mass of nitrogen = (16 x 14) = 224

Now, we add all of these values together = 28 + 20 + 56 + 64 + 224 = 392

The answer is F.