Chem Lab 3: Synthesis of K2[Cu(C2O4)2(H2O)2]

synthesize
to make
potassiumdiaquadioxalatocuprate(II)
K2[Cu(C2O4)2(H2O)2]
metal complexes
a type of molecule that consists of a central metal atom covalently bonded to ions or molecules, called ligands; also called “coordination compounds” or “coordination complexes”; common in biological systems
coordinate covalent bond
the bond between a metal and a ligand; the ligand donates both electrons to the bond
heme group
iron-containing component of hemoglobin, which transports oxygen in the blood
What is the central atom of the diaquadioxalatocuprate(II) ion?
copper
The copper atom is bonded to what?
2 waters (H2O) and 2 oxalate groups (C2O4 2-) – the water and oxalate groups are the ligands
What donates the electrons to the covalent bond?
an oxygen on each group
monodentate ligands
ligands that bond to the metal through only one atom; like water
bidentate ligands
ligands that bond to metal through 2 atoms; oxalate
How many ligands in the diaquadioxalatocuprate(II) ion?
4 – (two H2O + two C2O4 2-)
How many bonding regions in the diaquadioxalatocuprate(II) ion?
6 – since the oxalate binds in two places
octahedral geometry
the diaquadioxalatocuprate(II) ion, because there are four ligands and six bonding regions
stoichiometry of the reaction
a balanced chemical equation indicates the relative amounts of reactants required and the relative amounts of products that will be produced
an excess of one reactant is added to be sure that the other reactant, the ____ ___, is completely consumed
limiting reactant
limiting reactant
controls (limits) the extent of the reaction because when it has been consumed, the reaction can no longer occur; determines how much product can be produced
chemical reaction for the synthesis of potassium diaquadioxalatocuprate(II)
CuSO4 5H2O(aq) + 2K2C2O4H2O (aq) –> K2[Cu(C2O4)2(H2O)2](s) + K2SO4(aq) + 5H2O(l)
What is heated before mixing?
solutions of copper (II) sulfate pentahydrate and potassium oxalate monohydrate
Why is it heated before mixing?
the solubility of a substance increases with heat; this ensures that the salts are entirely dissolved and able to dissociate
Why to we allow the solution to slowly cool after mixing?
this allows the product to very slowly precipitate, because the solubility of the solids decreases as you cool the substance, and form a crystalline structure that reduces impurities
Why do we place the product in an ice bath?
to cool it further and to maximize the yield (amount of product we get)
theoretical yield
the maximum amount of product that can be produced
How can the limiting reactant be determined?
by calculating the theoretical yield of the reaction given the amount of each reactant used; the reactant that gives the lowest theoretical yield is the limiting reactant
How do you calculate the theoretical yield?
calculate the number of moles of your product that would be produced if all the reagent in question were converted to the product –> use the molar mass of the reactant to convert grams of reactant to moles of reactant, and then use the stoichiometry of the balanced chemical reaction to convert moles of reactant to moles of product, and finally use the molar mass of the product to determine the mass of the product that would be theoretically produced
percent yield
(experimental yield / theoretical yield) x 100%
experimental yield
the amount of product actually produced, which you find by massing your product; should always be less than the theoretical yield
Why should the experimental yield be less than the theoretical yield?
(1) issues with the the experimental design that can make it difficult to transfer all your crystals
(2) production of side products
(3) small amounts of of material typically remain in the solution and do not precipitate out
side products
in this case, and copper-containing products other than the product
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