# What is the formula mass of HNO_3?

Aug 11, 2016

The formula mass of $H N {O}_{3}$ is 63.02 g/mol

#### Explanation:

$\textcolor{g r e e n}{\text{We will use the formula below to answer the question:}}$

atomic weight of element $\times$number of atoms given by subscript $=$ molar mass

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

• H has an atomic weight of 1.008 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 hydrogen atom, so the atomic mass would just be 1.008 g/mol

There is also 1 nitrogen atom, so the atomic mass is just 14.01 g/mol

Next, you have 3 oxygen atoms, so you would multiply the atomic mass of O by 3 to obtain an atomic weight of 48.00 g/mol

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

$\textcolor{b l u e}{\text{1.008 g/mol + 14.01 g/mol + 48.00 g/mol = 63.02 g/mol}}$