# How many grams of glucose must be added to 275 g of water in order to prepare percent by mass concentration of aqueous glucose solution 1.30% ?

##### 1 Answer

#### Explanation:

The idea here is that the solution's **percent concentration by mass** tells you the number of grams of solute, which in your case is glucose, present **for every**

A solution that is **by mass** will contain

So the question is actually asking about the number of grams of glucose that must be added to **for every**

If you take **after** you add the glucose to the water, the **total mass** of the solution will be

#x quad "g" + "275 g" = (x + 275) quad "g"#

So you know that

This means that you have

#(x color(red)(cancel(color(black)("g glucose"))))/((x + 275) color(red)(cancel(color(black)("g solution")))) = (1.30 color(red)(cancel(color(black)("g glucose"))))/(100. color(red)(cancel(color(black)("g solution"))))#

Rearrange and solve for

#100. * x = 1.30 * x + 1.30 * 275#

#98.7 * x = 357.5 implies x = 357.5/98.7 = 3.6221#

Rounded to three **sig figs**, the number of sig figs you have for your values, the answer will be

#color(darkgreen)(ul(color(black)("mass of glucose = 3.62 g")))#