What is the molar mass of (NH4)2CO3?

96 g/mol

You just need to first get the atomic weights of the involved. You can easily get these from your periodic table.

Since I don't have one with me, I'll just use the rounded off version of the weights. But if you are going to do this properly, please use the weight with at least two decimal places for accuracy (e.g. 15.99 g/mol).

Also, please take note that I will be using the unit g/mol for all the weights. Thus,

Step 1

N = 14.00 g/mol H = 1.00 g/mol O = 16.00 g/mol C = 12.00 g/mol

Since your molecule is ##(NH_4)_2CO_3##, I would need to multiply the weights with respect to their subscripts. Therefore,

Step 2

N = 14.00 x 2 = 28.00 g/mol H = 1.00 x (4x2) = 1.00 x 8 = 8.00 g/mol O = 16.00 x 3 = 48.00 g/mol C = 12.00 x 1 = 12.00 g/mol

The molar mass is the mass of of given substance divided by the amount of the substance. So to get the mass of the substance, we need to add all the weights from Step 2.

Step 3

molar mass of ##(NH_4)_2CO_3## = 28.00 + 8.00 + 48.00 + 12.00 molar mass of ##(NH_4)_2CO_3## = 96.00 g/mol