What is the formula mass for #Sr(NO_3)_2#?

1 Answer
Dec 19, 2016


#211.64 g/(mol)#


#color(magenta)"We will use the formula below to answer the question:"#

atomic weight of element #xx#number of atoms given by subscript #=# formula mass

First, you want to have a periodic table available so you can determine the atomic weight of Sr, N, and O:

  • Sr has an atomic weight of 87.62 g/mol
  • N has an atomic weight of 14.01 g/mol
  • O has an atomic weight of 16.00 g/mol

From the chemical formula, we have 1 strontium atom, so the atomic weight of Sr is just 87.62 g/mol.

There are 2 nitrogen atoms, so the atomic mass has to be multiplied by 2, which gives you a value of 28.02 g/mol

Next, you have 6 oxygen atoms, so you would multiply the atomic mass of O by 6 to obtain an atomic weight of 96.00 g/mol

Now you want to add the mass of each atom together to obtain the formula mass of the entire compound:

#color(purple) ("87.62 g/mol + 28.02 g/mol + 96.00 g/mol = 211.64 g/mol")#