Synthesis and Analysis of a Cobalt Amine Halide Complex

Vocabulary flashcards covering key terms from the cobalt amine halide complex lab and discussion.

Coordination complex

A compound with a central metal atom bound to surrounding ligands via coordinate covalent bonds.

Central metal atom

The metal at the center of a coordination complex (here, cobalt).

Coordination number

The number of ligand donor atoms bonded to the central metal in a coordination complex.

Valency number

The traditional valence (oxidation state) of the metal; different from coordination number.

Ligand

An ion or neutral molecule that donates electrons to bind to the central metal.

Coordinate covalent bond

A bond formed when a ligand donates both electrons to the bond with the metal.

Lewis acid

A species that accepts electrons in a Lewis acid–base sense.

Lewis base

A species that donates electron pairs to form bonds with a Lewis acid.

NH3 ligand

Ammonia acting as a donor ligand to cobalt in the complex.

Co3+ oxidation state

Cobalt in the +3 oxidation state, achieved by oxidation (e.g., with H2O2).

Hydrogen peroxide (H2O2)

An oxidizing agent used to oxidize cobalt to Co3+ in this synthesis.

Halide ion

Cl− or Br−, ligands that balance charge and participate in coordination to cobalt.

Cobalt amine halide complex

A coordination complex where cobalt is bound to ammonia ligands and halide ligands.

Coordination number 6

Six ligands bound to the central cobalt atom in the complex.

Activated charcoal

Carbon used to adsorb impurities during purification steps.

Filtration

Separation of solids from liquids; techniques include gravity or suction (vacuum) filtration.

Gravity filtration

Filtration driven by gravity using fluted filter paper.

Suction (vacuum) filtration

Filtration using vacuum to pull liquid through filter paper.

Evaporation

Reducing solvent volume to concentrate solution (e.g., to 1/3 or 2/3 of original).

Stopping point

Predefined point at which to stop a synthesis step (depends on synthesis number).

Synthesis numbers

Six procedures (Synth. 1–6) with different cobalt sources and halide sources.

CoCO3

Cobalt carbonate, a cobalt source used in several syntheses.

CoCl2·6H2O

Cobalt chloride hexahydrate, a cobalt source for Synth 2 and 3.

CoBr2·6H2O

Cobalt bromide hexahydrate, a cobalt source for Synth 5.

NH4OH(aq)

Aqueous ammonium hydroxide; provides NH3 and OH− during synthesis.

NH4Cl(s)

Ammonium chloride solid; halide source for some syntheses.

NH4Br(s)

Ammonium bromide solid; halide source for some syntheses.

HCl

Hydrochloric acid; halide source in Synth 1–3.

HBr

Hydrobromic acid; halide source in Synth 4–6.

Tape marks

Tape used to mark evaporation levels (e.g., 2/3 or 1/3) to guide stopping points.

Parafilm

Stretchable film used to seal beakers and prevent evaporation.

Ice bath

Cold bath used to cool solutions after heating.

Beaker labeling

Label beakers with name and desk number for identification.

Waste disposal

Direct liquid waste to acid waste; ammonium-containing waste to basic waste; all rinses in hood.

Cobalt limiting reagent

Cobalt is the limiting reactant in this synthesis; weighed to four decimals.

∆Tb = i·k_b·m

Boiling point elevation equation: change in boiling point equals van't Hoff factor times k_b times molality.

van’t Hoff factor

i; number of particles formed from a dissolved solute; used in colligative property calculations.

Molality (m)

Moles of solute per kilogram of solvent; used in ∆Tb = i·k_b·m.

Coordination of Co3+

Arrangement of ligands around cobalt in the +3 oxidation state, typically six coordination sites.

Cl- vs Br- halide difference

Synth 1–3 use Cl− as halide source; Synth 4–6 use Br− as halide source.