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burette clamp

Titration. burette clamp. burette. erlenmeyer flask. ring stand. Describe an acid/base titration. Compare and contrast the end point and the equivalence point of a titration. Determine the concentration of an unknown acid or base using titration data.

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burette clamp

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  1. Titration burette clamp burette erlenmeyer flask ring stand

  2. Describe an acid/base titration. • Compare and contrast the end point and the equivalence point of a titration. • Determine the concentration of an unknown acid or base using titration data. • Determine the mass of an unknown acid or base using titration data

  3. Titration – controlled neutralization reaction. • Used to measure [ ] of unknown acid or base. • A standard solution is required. HA + BOH  BA + H2O salt water Standard solution – solution of a strong acid or base of known concentration. **pH does not indicate concentration because weak acids/bases do not dissociate completely.

  4. Titration Apparatus burette clamp burette buret ring stand erlenmeyer flask

  5. Equivalence point – amount of standard added neutralizes the unknown sample. moles H+ = moles OH- (pH = 7) • Endpoint – the indicator changes colour. • Determined by adding a pH indicator. Eq. point - defined by reaction stoichiometry. Endpoint - determined by the choice of indicator.

  6. Measured amount of acid of unknown • concentration is added to the flask. • An appropriate indicator is added to the • unknown. • 3. Measured amount of base of known concentration is added slowly to the flask. • 4. The titration is stopped when a colour • change has occurred (end point). • Concentration of the acid is calculated. **Titration can also be preformed with a calculated volume of standard in the flask, and the unknown in the buret.

  7. HCl(aq) + NaOH(aq) NaCl(aq) + H2O(l) Calculate the concentration of hydrochloric acid, if 25.00 mL is just neutralized by 40.00 ml of a 0.150 mol/L sodium hydroxide solution. 0.150 mol 0.04 L = 0.006 moles NaOH 1 L 1:1 ratio 0.00600 moles of HCl 0.006 mol = 0.240 M HCl 0.025 L

  8. H2CO3(aq) + 2 NaOH(aq) Na2CO3(aq) + 2 H2O(l) What volume of a 0.250 mol/L solution of carbonic acid is needed to neutralize 30.0 g of sodium hydroxide. Molar mass of NaOH = 40.0 g 30.0 g 1 mole = 0.750 moles NaOH 40.0 g

  9. 2:1 ratio 0.750 mol 1 H2CO3 = 0.375 moles H2CO3 2 NaOH 0.375 mol 1 L = 1.5 L H2CO3 0.250 mol 1.5 L of 0.250 mol/L H2CO3 will neutralize 30.0 g of NaOH

  10. HCl(aq) + NaOH(aq) NaCl(aq) + H2O(l) Determine the concentration of a hydrochloric acid solution using a 0.100 mol/L solution of NaOH Indicator - phenolphthalein (endpoint turns pink)

  11. HCl(aq) + NaOH(aq) NaCl(aq) + H2O(l) 1. Calculate the moles of base used: 0.100 mol 0.01383 L = 0.001383 mol NaOH 1 L 2. Use stoich to determine moles of acid used: 1:1 ratio 0.001383 moles of HCl 3. Calculate unknown value. 0.001383 mol = 0.121 M HCl 0.01144 L

  12. Titration Curves

  13. Plotting pH values during a titration gives a titration curve. Type of curve produced accounts for 2 classes of titrations: 1. Strong acid titrated with strong base. 2. Strong base titrated with strong acid. 3. Weak acid titrated with strong base. 4. Weak base titrated with strong acid.

  14. SA - SB The equivalence point is the centre of the steepest portion of the curve.

  15. SB - SA

  16. WA - SB Phenolphthalein not suitable indicator.

  17. WB - SA

  18. Eqv pt of a SA-SB / SB-SA titration is at pH = 7. • Eqv pt of a WA-SB titration had a pH > 7. • Eqv pt of a WB-SA titration has a pH < 7. • Chose indicator that changes colour (end point) near the expected Eqv pt.

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