# What is the molar mass of lithium oxide, Li_2O?

Jul 13, 2016

#### Answer:

color(red)("29.88 g/(mol))

#### Explanation:

$\textcolor{p u r p \le}{\text{Let's use this equation to answer the question:}}$

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

First, you want to have your handy dandy periodic table available so you can determine the atomic weight of Li and O:

Li has an atomic weight of 6.94 g/mol
O has an atomic wight of 16.00 g/mol

Based on the chemical formula, we have 2 atoms of Li, so the atomic weight of Li has to be multiplied by 2 to obtain 13.88 g/mol.

You have 1 atom of O, so the atomic mass would just be 16.00 g/mol

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

$\textcolor{red}{\text{13.88 g/mol + 16.00 g/mol = 29.88 g/mol}}$

$L {i}_{2} O$ is composed of Lithium and Oxygen atoms.

If you refer to your periodic table, the atomic weight is the molar mass of each element.

The molar mass of Lithium is 6.9 g/mol and Oxygen 16.0 g/mol.

Since there are 2 atoms of Lithium - if you look closely in $L {i}_{2} O$,
the molar mass of lithium $L {i}_{2} O$ is 6.9 $\times$ 2 = 13.8 g/mol.

Add the molar masses of Lithium and Oxygen together:
13.8 g/mol + 16.0 g/mol therefore the molar mass of Lithium oxide is 29.8 g/mol.