96.08462 grams
96.08462 grams/mole
The formula mass of a substance is simply the sum of the atomic weights of the atoms in the substance. So let's start by looking up the atomic weights.
Atomic weight nitrogen = 14.0067
Atomic weight hydrogen = 1.00794
Atomic weight carbon = 12.0107
Atomic weight oxygen = 15.999
Looking at the formula (NH4)2CO3, we have 2 nitrogen, 8 hydrogen, 1 carbon, and 3 oxygen atoms. So the formula mass is:
2 * 14.0067 + 8 * 1.00794 + 12.0107 + 3 * 15.999 = 96.08462 grams
And conveniently, the molar mass of a substance is exactly the same as the formula mass. So it too is 96.08462 grams/mol
