Consumer product analysis Flashcards
Define fractional distillation
technique used to separate liquids with narrow range of b.p
Define simple distillation
Technique used to separate liquids with significantly different b.p
How can purity be determined by M.P
PURE substances have a sharply defined M.P (range of 1-2deg) while impure substances have both lower and broader melting temp.
Why does impure have lower M.P
Bc the impurities disrupt and weaken the overall molecular or lattice structure, meaning less energy is required to overcome the forces of attraction in the solid.
What may the results of MP techniques suggest
-If the range is lower and broader than that of the known pure sample, then compound is not pure or is a mixture of impure compounds
-If lower yet well-defined, the unknown substance is likely a mixture of pure compounds
Why do impurities increase B.P
-Impurities can introduce additional intermolecular forces
-Impurities can disrupt the regular lattice structure which can increase bp
(-decrease vapour pressure)
Describe difference between simple and fractional distillation
The fractioning column allows continuous changes from l to g and back, this results in a much purer fraction than with simple distillation where mixtures need to be distilled multiple times to obtain pure distillate.
Why choose distillation over MP
Measuring bp is preferred method for many volatile compounds as the mp is too low.
What are 4 sources for error (titration)
Error standardising _____ solution
Another reductant other than ______ reacting with _____
Oxidised by atmoshpheric O2 -> unknown M of solution
Endpoint may have been inaccurate reflection of equivalence point
