# What is the percent by mass of glucose in a solution containing 0.15 moles of glucose dissolved...

## Question:

What is the percent by mass of glucose in a solution containing {eq}0.15 {/eq} moles of glucose dissolved in {eq}410\ g {/eq} acetic acid? The molar mass of glucose is {eq}180\ g/mol {/eq}.

## Converting Between Mass and Number of Moles

The amount of a chemical species may be specified using colloquial units including grams, kilograms (for solids), and liters, cubic centimeters (for liquids and gases). Alternatively, we may use a unit peculiar to chemistry - the mole. The link between the mole and the mass in grams is the molar mass of the element or the compound. The unit of molar mass is g/mol. For elements it may be obtained directly from the periodic table, but for compounds, it has to be computed from the molecular formulae.

We have 0.15 moles of solute (glucose), whose molar mass is 180 g/mol. How many grams are these? We multiply:

{eq}0.15 \ mol \times 180 \ g/mol = 27 \ g {/eq}.

The mass of the solvent (acetic acid) is 410 g. Hence, the total mass of the solution is:

{eq}410 \ g + 27 \ g = 437 \ g {/eq}.

The percentage by mass of glucose is obtained as:

{eq}\displaystyle \frac{27 \ g}{437 \ g} \times 100\% = 6.18\% {/eq}