A chemist adds 0.40 of a 1.4''M'' aluminum chloride (AlCl_3) solution to a reaction flask....

Question:

A chemist adds 0.40 of a 1.4M aluminum chloride {eq}(AlCl_3) {/eq} solution to a reaction flask. Calculate the mass in grams of aluminum chloride the chemist has added to the flask.

Converting Moles to Mass in Grams

A mole is a unit of measurement of quantity of a chemical species. By using the notion of the molar mass, one can convert this into grams. The molar mass of any element can be obtained by inspecting a periodic table, and that of a compound can be calculated by summing up the masses of each element multiplied by the number of its atoms in that compound.

The chemist has added 0.40 L of a 1.4 M solution. How many moles are in this solution? We compute:

{eq}\displaystyle 0.40 \ L \times 1.4 \ mol/L = 0.56 \ mol {/eq}.

The molar mass of aluminium chloride is:

{eq}(27) + 3(35.5) = 133.5 \ g/mol {/eq}

Finally, the mass of the aluminium chloride salt is:

{eq}0.56 \ mol \times 133.5 \ g/mol = 74.76 \ g {/eq}. 