Concentration Examples in Chemistry

Start with the recap, study the fully worked examples, then use the practice problems to check your understanding of Concentration.

This page combines explanation, solved examples, and follow-up practice so you can move from recognition to confident problem-solving in Chemistry.

Concept Recap

The quantity of solute dissolved per unit volume of solution, most commonly expressed as molarity (M) in units of moles per liter (mol/L). Concentration quantifies how much solute is present relative to the total solution volume.

How 'strong' a solution is—more solute in the same volume = more concentrated.

Read the full concept explanation →

How to Use These Examples

  • Read the first worked example with the solution open so the structure is clear.
  • Try the practice problems before revealing each solution.
  • Use the related concepts and background knowledge badges if you feel stuck.

What to Focus On

Core idea: Molarity (M) is the most common concentration unit — moles of solute per liter of solution.

Common stuck point: Molarity is moles per liter of solution (including the solute), not per liter of pure solvent.

Sense of Study hint: When solving concentration problems, identify what you know: moles, volume, or molarity. First convert mass to moles if needed using molar mass. Then ensure volume is in liters (divide mL by 1000). Finally, apply M = n/V to find the unknown quantity.

Worked Examples

Example 1

easy
Calculate the molarity of a solution made by dissolving 5.85 g of NaCl in water to make 500\,\text{mL} of solution. (NaCl molar mass = 58.44\,\text{g/mol})

Solution

  1. 1
    Moles of NaCl = \frac{5.85}{58.44} = 0.100\,\text{mol}.
  2. 2
    Volume in liters = 500\,\text{mL} = 0.500\,\text{L}.
  3. 3
    Molarity = \frac{n}{V} = \frac{0.100}{0.500} = 0.200\,\text{M}.

Answer

0.200\,\text{M}
Molarity (M) is the most common concentration unit in chemistry. It measures moles of solute per liter of solution, not per liter of solvent.

Example 2

medium
How many grams of KOH are needed to prepare 250\,\text{mL} of a 0.40\,\text{M} solution? (KOH = 56.11\,\text{g/mol})

Example 3

medium
Calculate the molarity of a solution made by dissolving 5.85 g of NaCl (molar mass 58.5 g/mol) in enough water to make 500 mL.

Practice Problems

Try these problems on your own first, then open the solution to compare your method.

Example 1

easy
What is the molarity of a solution containing 0.50 mol of solute in 2.0 L?

Example 2

easy
What is the molarity of a solution made by dissolving 0.750 mol of \text{KNO}_3 in enough water to make 2.50 L of solution?
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Background Knowledge

These ideas may be useful before you work through the harder examples.

molesolution