chem 116 quiz 2 Flashcards
simplified formula of Alum
M M,III (SO4)2 * 12H2O
M - alkali metal
M,III - trivalent ion
alums (are/are not) water soluble
are
taste of alums
astringent, acidic, sweet
alums react as ? with litmus (i.e., ?)
acids; turn blue litmus red
alums (are/are not) considered to be hydrate compounds
are
percent yield equals
(actual yield / theoretical yield) x 100%
alum used today for
hardening photographic film, preparing pickles, creating and fixing dyes
in the synthesis of alum, initially, the aluminum metal is ? to the aluminum ion
oxidized
alum reacts very slowly with acids because
it has an aluminum oxide coating that forms on it
aluminum metal will react more quickly with ? to produce the tetrahydroxoaluminate ion [Al(OH)4]-, so that is what is done in this experiment
bases such as KOH
slowly adding sulfuric acid to the tetrahydroxoaluminate solution causes ? to precipitate
aluminum hydroxide Al(OH)3
if excess acid is added, the solid aluminum hydroxide reacts with it and the ? ion is formed; the insoluble aluminum hydroxide will be converted to the soluble ? ion (same answer)
Al 3+
aluminum potassium sulfate dodecahydrate is (not soluble/very soluble) in hot water and (insoluble/soluble) in 95% ethanol
very soluble; insoluble
to precipitate the alum, the solution containing the dissolved aluminum sulfate and potassium sulfate is (cooled/heated)
cooled
filtration
the process by which a solid is separated from a liquid solution
gravity filtration
the simplest form of filtration; the solution that is to be filtered is poured through a filter paper fit into a filter funnel
gravity filtration is most often used when
the solid is being discarded and the filtrate (recovered solution) kept
two ways to fold the paper that will be placed in the filter funnel
simple (fold in half twice) and fluted (fold in half twice and then fold into eighths)
vacuum filtration
preferentially used to collect solids due to its speed and better drying capabilities
vacuum filtration is (slower/faster) than gravity filtration and why
faster; the solution is forced through the filter paper by the application of a vacuum
vacuum filtration is not used when?
to filter a solid from a liquid if it is the liquid that is to be kept and the liquid has a low boiling point
synthesis
the conversion of one substance to another
theoretical yield
the predicted amount of product that should be made using the stoichiometry of a reaction
what can cause the actual yield to be smaller than the theoretical?
incomplete reaction or mechanical losses in transfers, spills, or splashing
in this experiment the percent yield indicated the efficiency of
both the synthesis and recovery process
goal of any synthesis reaction
high percent yield
safety precautions of this lab
- eye protection
- wipe up any spills immediately with paper towels and rinse the area with water
- if you get the material on yourself, wash the area with copious quantities of water
- wash your hands before you leave the laboratory
- dispose of the liquids you collect in the waste container in the hood labeled for this purpose
product and filter paper to be disposed of
in the trash can
