Question

A chemist has a jar containing 388.2 g of iron filings. How many moles of iron does the jar contain?

Answer 1

no of moles = given mass / molar mass
                   =388.2/55.8
                   =6.95 moles

Answer 2

Given,

Amount of iron fillings contained in a jar of a chemist = 388.2 g

To find,

The number of moles equivalent to the given amount of iron filings in the jar.

Solution,

We can simply solve this numerical problem by using the following process:

As per stoichiometry;

1 mole of any element contains Avogadro's number of atoms, that is, 6.022 x 10^23 atoms.

And, the molar mass of any element is equal to the atomic mass of the same element.

{Statement-1}

The molar mass of iron fillings

= atomic mass of iron

= 55.85 grams

Now, according to the statement-1;

55.85 grams of iron fillings is equivalent to 1 mole of iron filings

=> 1 gram of iron fillings is equivalent to 1/55.85 moles of iron filings

=> 388.2 grams of iron fillings is equivalent to 1/55.85×388.2 moles, which is equal to 6.95 moles of iron fillings.

Hence, the jar contains 6.95 moles of iron fillings.