Question

A solution contains 15 ppm of benzene. The density of the solution is 1.00 g/mL. This means that ________.

the solution is 15% by mass of benzene
1.0 g of the solution contains 15 * 10^-6 g of benzene
there are 15 mg of benzene in 1.0 g of this solution
100 g of the solution contains 15 g of benzene
1.0 L of the solution contains 15 g of benzene

Answer 1

1.0 g of the solution contains 15 * 10^-6 g of benzene

Step-by-step explanation:

ppm by definition is parts per million. In this context, that means there are 15 g of benzene in 1,000,000 mL of solution.

We are given a solution with a density of 1.00 g/mL meaning there is just 1 mL

So, because there is only 1 mL instead of 1,000,000 mL, we will have 15 x 10^-6 g of benzene present in 1 g of the solution.

Answer 2

• second choice: 1.0 g of the solution contains 15 × 10⁻⁶ g of benzene.

Step-by-step explanation:

ppm is a unit of concentration that means parts per million. In grams that is grams of solute per one million (10⁶) grams of solution.

Then, 15 ppm of benzene means that there are 15 grams of benzen in 1,000,000 grams of solution.

That leads to:

• 1,000,000 g solution / 15 g benzene

Multiplying numerator and denominator by 10⁻⁶ you find:

• 1,000,000 × 10⁻⁶ g solution / (15 × 10⁻⁶ g benzene)

Simplifying:

• 1.0 g solution / (15 × 10⁻⁶ g benzene)

Which is read as 1.0 g of the solution contains 15 × 10⁻⁶ g of benzene, i.e. the second answer choice.