# Question bfee2

Dec 16, 2015

Here's what I got.

#### Explanation:

I'll show you how to solve part (C), and leave the first two to you as practice.

As you know, molarity is defined as moles of solute per liters of solution. Practically, a solution's molarity tells you how many moles of solute you get in one liter of solution.

$\textcolor{b l u e}{\text{molarity" = "moles of solute"/"liters of solution}}$

This means that in order to calculate the molarity of a given solution, you need to know two things

• how many moles of solute you have
• what the volume of the solution is - expressed in liters

For part (C), your solute will be glucose, ${\text{C"_6"H"_12"O}}_{6}$. In order to determine how many moles of glucose you have in that mass, you need to use the compound's molar mass.

Molar mass tells you what the mass of one mole of a substance is. Glucose has a molar mass of $\text{180.16 g/mol}$, which means that one mole of glucose has a mass of $\text{180.16 g}$.

Now, notice that your mass is given in milligrams, $\text{mg}$. This means that you need to convert to grams first, then use the molar mass to find the number of moles

295 color(red)(cancel(color(black)("mg"))) * "1 g"/(1000color(red)(cancel(color(black)("mg")))) = "0.295 g"

This means that you have

0.295 color(red)(cancel(color(black)("g"))) * ("1 mole C"_6"H"_12"O"_6)/(180.16 color(red)(cancel(color(black)("g")))) = "0.001637 moles C"_6"H"_12"O"_6

Now focus on finding the volume of the solution in liters

63.2 color(red)(cancel(color(black)("mL"))) * "1 L"/(1000color(red)(cancel(color(black)("mL")))) = "0.06320 L"

The molarity of the solution will thus be

c = "0.001637 moles"/"0.06320 L" = color(green)("0.0259 M")#

For parts (A) and (B), you don't need to convert anything, since the mass is already given in grams and the volume of the solution in liters.