Starter quiz
- What is a mole?
- A unit of mass for small objects like atoms.
- The amount of substance containing Avogadro’s number of particles. ✓
- The volume of gas under standard conditions.
- The concentration of a solution in mol/dm³.
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- How do you calculate the number of moles from mass?
- number of moles = mass × relative formula mass
- number of moles = mass ÷ relative formula mass ✓
- number of moles = mass + relative formula mass
- number of moles = mass – relative formula mass
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- Calculate the number of moles in 50 g of NaCl (relative formula mass of NaCl = 58.5).
- '0.85' ✓
- How do you calculate concentration in mol/dm³?
- concentration = number of moles ÷ volume (in cm³)
- concentration = number of moles × volume (in cm³)
- concentration = number of moles × volume (in dm³)
- concentration = number of moles ÷ volume (in dm³) ✓
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- How do you convert cm³ to dm³?
- multiply the volume in cm³ by 1000
- multiply the volume in cm³ by 10
- divide the volume in cm³ by 1000 ✓
- divide the volume in cm³ by 10
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- Convert 250 cm³ to dm³.
- '0.25' ✓
Exit quiz
- Match the following key words to their definition.
- titration⇔A technique to find exact volumes of reacting solutions. ✓
- titre⇔The volume of titrant needed to reach the end point. ✓
- concordant⇔Readings within ±0.10 cm³ of each other. ✓
- coefficient⇔A number showing the ratio of substances in a reaction. ✓
- mole⇔1 mole contains 6.02 × 10²³ particles. ✓
- Why are concordant titres important?
- They ensure the solution has been accurately neutralised.
- They show when the reaction is complete.
- They allow chemists to calculate a precise average volume. ✓
- They help determine the end point of the titration.
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- What is the stoichiometric ratio of HCl to NaOH in the balanced equation below? HCl + NaOH → NaCl + H₂O
- '1 : 1' ✓
- Calculate the number of moles in 18.5 g of NaOH (relative formula mass = 40).
- '0.463' ✓
- In a titration, 20 cm³ of 0.5 mol/dm³ HCl neutralises 40 cm³ of NaOH. The balanced equation is: HCl + NaOH → NaCl + H₂O What is the concentration of the NaOH?
- 0.25 mol/dm³ ✓
- 0.5 mol/dm³
- 0.125 mol/dm³
- 1 mol/dm³
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- In a titration, 25 cm³ of 0.4 mol/dm³ H₂SO₄ neutralises 75 cm³ of KOH. The balanced equation is: H₂SO₄ + 2KOH → K₂SO₄ + 2H₂O What is the concentration of the KOH in mol/dm³ to 3 d.p.?
- '0.267' ✓
Worksheet
Presentation
Video
Lesson Details
Key learning points
- Data collected during a titration allows chemists to determine a solution’s unknown concentration.
- Concordant titres should be used when calculating a mean volume used to neutralise a solution.
- The coefficients in a balanced equation indicates the stoichiometry (i.e. molar ratio) between substances in a reaction.
- The concentration of an unknown solution is found using the relationship: concentration = moles ÷ volume (in dm³).
Common misconception
Pupils use all of their titration results to calculate an average volume used during titration. Pupils also tend to miss steps in this multi-step process.
Stress the need to use concordant results when calculating an average volume for neutralising a solution via titration. Use a calculation grid to help keep each calculation step clearly organised.
Keywords
Titration - A technique in volumetric analysis that is used to find the exact volumes of solutions that react with each other.
Titre - The volume of titrant needed to reach the end point in a titration.
Concordant - Readings within a certain range. For titrations, these usually need to be within 0.10 cm³ of each other.
Coefficient - The number placed in front of a chemical formula to balance an equation; it shows the ratio of substances in a reaction.
Mole - 1 mole contains 6.02 × 10²³ particles. The mass of a mole of a substance is its relative mass expressed in grams.