Answer to Question #207809 in General Chemistry for HPrudencio

Question

A 3.95 g sample of a laboratory solution contains 1.10 g of acid. What is the concentration of the solution as a mass percentage?

Answer 1

As you know, a solution contains a solute and a solvent, which more often than not is water. This means that a solution's % m/m

 concentration tells you how many grams of solute and grams of solvent must be mixed to get 100 g of solution.

 you know that you get 1.10g of acid in 3.95 g

 of solution. To find the solution's percent concentration by mass, use this as a conversion factor to figure out how many grams of solute you'd get in 100 g of solution

$100gSolution × \frac{1.10g Of Acid}{3.95gsolution} = 27.84$ %

As mentioned before, you can use the solution's percent concentration by mass to say that 100 g of solution will contain

100g - 27.84g = 72.16g

In other words, you can make this solution by adding 27.84 g of acid for every 72.16 g of water, which of course gets you 30.5 g of acid per 100 g of solution.