Question

What is the molarity of an aqueous solution containing 22.5 grams of glucose in 25.5 mL of solution?

Answer 1

`"4.90 mol L"^(-1)`

Explanation:

Start by calculating the number of moles of glucose present in `"25.5 mL"` of solution.

To do that, use the molar mass of glucose

`22.5 color(red)(cancel(color(black)("g"))) * "1 mole glucose"/(180.156color(red)(cancel(color(black)("g")))) = "0.1249 moles glucose"`

Now, in order to find the molarity of the solution, you need to determine the number of moles of solute present in `"1 L" = 10^3` `"mL"` of solution.

The fact that you're dealing with a solution, which, as you know, is a heterogeneous mixture, i.e. it has the same composition throughout, you can use the known composition as a conversion factor to find the number of moles of solute present in `10^3` `"mL"` of solution.

`10^3 color(red)(cancel(color(black)("mL solution"))) * "0.1249 moles glucose"/(25.5color(red)(cancel(color(black)("mL solution")))) = "4.898 moles glucose"`

You can thus say that the molarity of the solution is equal to

`color(darkgreen)(ul(color(black)("molarity = 4.90 mol L"^(-1))))`

The answer is rounded to three sig figs.