Question

What is the percentage of lithium in lithium carbonate `Li_2CO_3`?

Answer 1

Molar mass of Lithium `-:` Molar mass of Lithium Carbonate `xx` 100 = ??

Explanation:

First step, find the molar mass of `Li_2CO_3`.

The molar mass is same as atomic weight on the periodic table.

But you have to see what elements are present in this formula. You can see that Lithium, Carbon and Oxygen are present.
The molar mass of:
Lithium = 6.9 g/mol
Carbon = 12.0 g/mol
Oxygen = 16.0 g/mol

Since there are 2 lithiums, 3 oxygens, and one carbon, the molar mass for `Li_2CO_3` is:

[`2 xx 6.9 + 1 xx 12.0 + 3 xx 16.0`] = 73.8 g/mol.

Li: `2 xx 6.9` = 13.8 g/mol

The percentage of Lithium in `Li_2CO_3` is:
13.8 `-:` 73.8 `xx` 100 = 18.7%