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

Dec 19, 2016

$211.64 \frac{g}{m o l}$

#### Explanation:

$\textcolor{m a \ge n t a}{\text{We will use the formula below to answer the question:}}$

atomic weight of element $\times$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:

$\textcolor{p u r p \le}{\text{87.62 g/mol + 28.02 g/mol + 96.00 g/mol = 211.64 g/mol}}$