Final answer:
The formula mass of calcium nitrate, Ca(NO₃)₂, is 164.08 amu.
Step-by-step explanation:
The formula mass of calcium nitrate, Ca(NO₃)₂, is 164.08 amu.
When a formula contains more than one polyatomic unit, such as Ca(NO3)2, you need to multiply the atomic mass of every atom inside the parentheses by the subscript outside the parentheses. So, for Ca(NO3)2, the subscript 2 implies two complete nitrate ions, so you must sum the masses of two (1 × 2) nitrogen atoms and six (3 × 2) oxygen atoms, along with the mass of a single calcium atom:
Ca: 1 x 40.08 = 40.08 amu
N: 2 x 14.00 = +28.00 amu
O: 6 x 16.00 = +96.00 amu
Total: 164.08 amu