Analysis & quantitative Chemistry
- Created by: Fionnuala Smith
- Created on: 02-02-13 14:26
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- Analysis & Quantitative Chemistry
- Flame tests
- Used to identify metal ions
- Green - Barium, Brick Red - Calcium, Crimson - Lithium, Lilac - Potassium, Yellow - Sodium
- Heat & dip nichrome wire in concentrated hydrochloric acid to clean
- Dip wire in compound
- Put in bunsen flame
- Dip wire in compound
- Reacting carbonates with dilute acid
- Carbonates react with dilute acids to form CO2 (and a salt and water). CO2 turns lime water cloudy
- e.g. Calcium Carbonate + hydrochloric acid = calcium chloride + carbon dioxide + water
- Precipitation of Metal Ions
- Metal compounds in solution contain metal ions
- Some form precipitates i.e. insoluble solids that come out of solution when sodium hydroxide's added
- Al3+ (aq) - white precipitate which dissolves in excess sodium hydroxide
- Ca2+ (aq) - white, Mg2+ - white, Cu2+ (aq) - blue, Fe2+ (aq) - green, Fe3+ (aq) - Brown
- Fe2+ = Iron ( II) & Fe3+ = Iron (III). All precipitates formed are hydroxides e.g. Calcium hydroxide
- Metal compounds in solution contain metal ions
- More examples of precipitation
- If dilute hydrochloric acid and barium chloride are added to a solution containing sulfate ions, a white precipitate of barium sulfate is produced
- Precipitates with silver nitrate solution can be produced by Halide ions (chloride, bromide, iodide ions) in solution in presence of dilute nitric acid:
- Silver Chloride - white, Silver Bromide - cream, Silver Iodide - yellow
- Titration
- Used to find out how much of an acid is needed to neutralise an alkali
- Neutralisation = hydrogen ions (H-) from acid and hydroxide ions (OH-) from alkali form water
- Clean pippette to measure out known & accurate volume of alkali
- Put alkali in clean conical flask.
- Add suitable indicator e.g. phenolphthalein
- Put acid in burette (cleaned with acid) and take reading of volume.
- Add acid to alkali until indicator changes to green (neutral). This is called the end point.
- Take final reading of volume in burette.
- Subtract final reading from initial reading to find volume of acid added
- Method can be used to obtain salt without using an indicator. Method can be repeated to check results.
- Subtract final reading from initial reading to find volume of acid added
- Take final reading of volume in burette.
- Add acid to alkali until indicator changes to green (neutral). This is called the end point.
- Put acid in burette (cleaned with acid) and take reading of volume.
- Add suitable indicator e.g. phenolphthalein
- Put alkali in clean conical flask.
- Indicators
- Different strength acids & alkalis can react together to form a neutral solution.
- Suitable indicator for strong acids & alkalis = acid based (e.g. litmus)
- Titration - Higher
- can be used to find concentration of acid/alkali
- You must know: relative volumes & concentration of other acid/alkali
- 1) Write balanced equation for reaction to determine ratio of moles of acid to alkali involved
- 2) Calculate no. of moles in solution of known volume & concentration ( you know the nuimber of moles in other solution from previous calc.)
- Calculate concentration of other solution: Number of moles of solute (mol) / Volume of solution (dm^-3)
- can be used to find concentration of acid/alkali
- Flame tests
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