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Titrations. About Titrations. Volumetric analysis– a technique for determining the amount of a certain substance by doing a titration. Titrant - the substance delivered from a buret so that its volume is accurately known. The solution with a known concentration will be used as a titrant
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About Titrations • Volumetric analysis– a technique for determining the amount of a certain substance by doing a titration. • Titrant- the substance delivered from a buret so that its volume is accurately known. • The solution with a known concentration will be used as a titrant • Analyte- the substance being analyzed; its mass or volume must be accurately known • This is the unkown solution in the beaker below the buret.
Example A solution of potassium dichromate is standardised by titration with sodium ethanedioate solution of concentration 0.0925 mol.dm-3. If 47.0cm3 of the dichromate solution were needed to oxidise 25.0cm3 of the sodium ethanedioate solution, what is the concentration of the potassium dichromate solution?
First step: Write out balanced reaction • K₂Cr₂O₇ + Na₂C₂O₄ Na₂Cr₂O₇ + K₂C₂O₄ 47.0 cm³ 25.0 cm³ M= ? M= .0925 mol/ dm³ = .492 mol/ cm³
Hints • Looking for the molecular formula • Given % assume you have 100 grams • Find moles of each element in compound • Find ratio in empirical • Find empirical molar mass • 1 acidic hydrogen … 1:1 ratio with base (NaOH) • Find molar mass (g/mol) • Find ratio • Give molar mass • Convert mL to L otherwise your M is mmol/m