Question

What is the mass in grams of 5.40 moles of lithium.

Answer 1

Answer: The mass of lithium is 34.7 grams.

Explanation:

To calculate the mass of lithium for given number of moles, we use the equation:

$\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}$

We are given:

Number of moles of lithium = 5.40 moles

Molar mass of lithium = 6.94 g/mol

Putting values in above equation, we get:

$5.40mol=\frac{\text{Mass of lithium}}{6.94g/mol}\\\\\text{Mass of lithium}=(5.0mol\times 6.94g/mol)=34.7g$

Hence, the mass of lithium is 34.7 grams.

Answer 2

You would use the formula:

n = $\frac{m}{M}$

Where m is the mass, and M is molar mass (the periodic table would be used for this)

In this case, we need to rearrange the formula to find m

m = nM
    = 5.40 x 6.941
    = 37.5g

Hope this helped! Ask me if there's any part of the working you don't understand :)