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Titration calculations

Titration calculations. Learning Objective : Understand how to calculate concentration from reacting volumes Learning Outcome : Use balanced symbol equations to calculate the concentration of an unknown reactant (A/A*). Last lesson…. HCl Concentration ? Volume = your average titre. NaOH

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Titration calculations

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  1. Titration calculations Learning Objective: • Understand how to calculate concentration from reacting volumes Learning Outcome: • Use balanced symbol equations to calculate the concentration of an unknown reactant (A/A*)

  2. Last lesson….. HCl Concentration ? Volume = your average titre NaOH Concentration = 0.1 mol dm-3 Volume = 25 cm3

  3. Concentration = no. of moles volume • Learn this formula triangle! number of moles n concentration (in moldm-3) volume (in dm3) c v

  4. 1 litre = 1000 cm3 = 1 dm3 Concentration • Concentration is a measure of how crowded things are. • The concentration can be measured in moles per dm3 (ie. moles per litre). • So 1 mole of ‘stuff’ in 1dm3 of solution has a concentration of 1 mole per dm3 (1mol/dm3). • The more solute you dissolve in a given volume, the more crowded the solute molecules are and the more concentrated the solution.

  5. using the triangle • Example 1: What is the concentration of a solution with 2 moles of salt in 500cm3? The question already tells us the number of moles and the volume, so use the formula: c = n = 2 = 4 mol/dm3 v 0.5 convert the volume to dm3 first by dividing by 1000.

  6. Example 2: How many moles of sodium chloride are in 250cm3 of a 3 mol dm-3 solution of sodium chloride? The question tells us the volume and concentration, so use the formula: n = c x v = 3 x 0.25 = 0.75 moles convert the volume to dm3 first by dividing by 1000.

  7. What happens next? “In a titration, 20 cm3 of 1.0 mol dm-3hydrochloric acid, HCl, reacted with 25 cm3 of sodium hydroxide, NaOH. What was the concentration of the sodium hydroxide?” • You will need to write a balanced symbol equation. • Use the crib sheets available (2 options)

  8. Common formula • Hydrochloric acid = HCl • Nitric acid = HNO3 • Sulphuric acid = H2SO4 • Sodium hydroxide – NaOH • Sodium sulphate = Na2SO4 • Sodium nitrate = NaNO3 • Phosphoric acid = H3PO4 • Sodium phosphate = Na3PO4 • Potassium sulphate = K2SO4

  9. answers Section A • 1.6 mol dm-3 • 0.08 mol dm-3 • 0.12 mol dm-3 • 0.912 mol dm-3 Section B • 1.6 mol dm-3 • 0.8 mol dm-3 • 2.4 mol dm-3 • 1.0 mol dm-3

  10. Using your average titre • Using your average titre from the previous lesson and calculate the concentration of HCl which was used to neutralise 25cm3 of 0.1mol dm-3NaOH. • Compare your result to the actual value. • Comment on the accuracy of your result.

  11. Titration calculations Learning Objective: • Understand how to calculate concentration from reacting volumes Learning Outcome: • Use balanced symbol equations to calculate the concentration of an unknown reactant (A/A*)

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