Sol - Solution Concentration (Lesson)

Solution Concentration

Introduction

In this lesson we will look at a way to quantitatively express concentration of solutions. You will learn how to calculate molarity of solutions using the amount of solute and volume of a solution.

Expressing Solution Concentration

In this segment of Chemistry Matters, our host describes ways to express solution concentration. The class learns about mass percent and the students propose plans for creating solutions with a known molarity.

Download the note taking guide for Chemistry Matters Unit 7 Segment C. Links to an external site.

Download the key to the questions to consider for Chemistry Matters Unit 7 Segment C. Links to an external site.

Preparing and Labeling a Solution Activity

The activity below will deepen your understanding of this concept.

Molarity

Let’s take a closer look at calculations involving Molarity.

Molarity = moles of solute/liters of solution

Things to remember when working molarity problems:

Volume must be in liters.
An uppercase M is used to denote molarity.
Use the molar mass of the substance (derived from the periodic table) to determine the moles if grams are given as the starting information

Example One

To make a 4.00M solution, how many moles of solute will be needed if 12.0 liters of solution are required?

Example Two

What is the molarity of a solution of HNO₃ that contains 12.6 grams HNO₃ in 1.0 L of solution?

Example Three

How many grams of potassium nitrate are required to prepare 0.250L of a 0.700 M solution?

Example Four

125 cm³ of a solution contains 3.5 moles of solute. What is the molarity of the solution?