Question

1. 15 g of four different solutes are added to four beakers, each containing 30 ml of water. the solute remaining after 2 minutes of agitation is removed from each of the beakers and weighed. which of the following solutions has the highest concentration?

	amount of water	initial amount of solute	final amount of solute
substance b	30 ml	15 g	5 g
substance c	30 ml	15 g	15 g
substance d	30 ml	15 g	0 g

a. substance a
b. substance b
c. substance c
d. substance d

Explanation:

Step1: Recall concentration formula

Concentration = $\frac{\text{Mass of solute}}{\text{Volume of solution}}$. Here volume of water (and assuming volume of solution is same as volume of water for simplicity) is constant ($30$ mL) for all substances. So, higher the mass of solute remaining, higher the concentration.

Step2: Compare final solute masses

Substance A has 15 g of solute remaining, Substance B has 5 g, Substance C has 15 g and Substance D has 0 g. Since the mass of solute remaining for Substance A and Substance C is the highest among all.

Answer:

A. Substance A, C. Substance C