1.9.1

Molarity

Test yourself

Molar Calculations of Solutions

We can calculate the number of moles of a liquid or solution using the volume and concentration.

Illustrative background for Heterogenous vs homogenous Illustrative background for Heterogenous vs homogenous  ?? "content

Heterogenous vs homogenous

  • Solutions are sometimes known as homogenous mixtures and can be liquid, solid, or gas.
    • In solutions, the constituents have the same proportions throughout the sample, so the macroscopic properties of the solution are consistent throughout.
  • Heterogeneous mixtures have a non-uniform composition and the macroscopic properties vary depending on the constituents.
    • In heterogeneous mixtures, you can separate the individual components. An example would be a cup of water with gravel in.
Illustrative background for Liquid solutionsIllustrative background for Liquid solutions ?? "content

Liquid solutions

  • Liquid solutions can be represented in a variety of ways. The most common way in a laboratory is "molarity".
  • It's much easier to look at a liquid and measure its volume than to evaporate any water and measure the mass of the remaining solid.
    • So we need a value that will let us know how much of a solid is dissolved in a solution simply from its volume.
  • If we know the concentration of a solution, we can calculate the number of moles in any sample volume of the solution.
Illustrative background for The equationIllustrative background for The equation ?? "content

The equation

  • Molarity is defined as moles per unit volume. The usual units of molarity are moles per liter (L).
  • So moles per liter is mol ÷ L.
    • This is often written as mol L -1 or just "M".
  • Molarity is sometimes written as moldm -3, where 1 L = 1 L. (Same thing, just different units!)
Illustrative background for contentIllustrative background for undefined ?? "content
Illustrative background for An exampleIllustrative background for An example ?? "content

An example

  • Three moles of NaCl are dissolved in half a liter of water.
    • Molarity = number of moles ÷ volume
    • Molarity = 3 mol ÷ 0.5 L
    • Molarity = 6 mol/L or 6 M

Jump to other topics

1Structure - Models of the Particulate of Matter

2Structure - Models of Bonding & Structure

3Structure - Classification of Matter

3.1The Periodic Table: Classification of Elements

3.2Periodic Trends

3.3Group 1 Alkali Metals

3.4Halogens

3.5Noble gases, group 18

3.6Functional Groups: Classification of Organic

3.7Functional Group Chemistry

3.8Alkanes

3.9Alcohols

3.10Halogenoalkanes

4Reactivity - What Drives Chemical Reaction?

5Reactivity - How Much, How Fast & How Far?

6Reactivity - The Mechanisms of Chemical Change

7Measurement, Data Processing & Analysis

Unlock your full potential with Seneca Premium

  • Unlimited access to 10,000+ open-ended exam questions

  • Mini-mock exams based on your study history

  • Unlock 800+ premium courses & e-books

Get started with Seneca Premium