This worked example covers Concentration Worked Example within Moles & Calculations for GCSE Chemistry. Revise Moles & Calculations in Quantitative Chemistry for GCSE Chemistry with 27 exam-style questions and 20 flashcards. This topic shows up very often in GCSE exams, so students should be able to explain it clearly, not just recognise the term. It is section 14 of 17 in this topic. Treat this as a marking guide for what examiners are looking for, not just a fact list.
🧮 Concentration Worked Example
Concentration measures how many moles of solute are dissolved in 1 dm³ of solution:
Question: 0.25 mol of NaOH is dissolved in 500 cm³ of water. Calculate the concentration in mol/dm³.
500 cm³ ÷ 1000 = 0.5 dm³
c = n ÷ V = 0.25 ÷ 0.5 = 0.5 mol/dm³
Answer: 0.5 mol/dm³
Always convert cm³ to dm³ first by dividing by 1000. Forgetting this step is the most common mistake in concentration calculations.
Practice questions for Moles & Calculations
One mole of any substance contains how many particles?
Explain why the percentage yield of a reaction is never 100% in practice.