Download Week #10: The Synthesis of a Compound using a Limiting Reagent

CH 103: THE SYNTHESIS OF A COMPOUND USING A LIMITING REAGENT
NiCl26H2O(aq) + 3H2NCH2CH2NH2(aq)  [Ni(H2NCH2CH2NH2)3]Cl2(s) + 6H2O(l)
• Stoichiometry is the numerical relationship between the moles of
reactants and the moles of products for a chemical reaction.
• What is the mole ratio of ethylenediamine (en, H2NCH2CH2NH2) to
nickel(II) chloride hexahydrate (NiCl26H2O)?
• The limiting reagent is the reactant that is completely consumed during
a chemical reaction. Therefore, the yield or amount of product formed
depends on the amount of limiting reagent.
• What is the limiting reagent if the actual mole ratio of
H2NCH2CH2NH2 / NiCl26H2O is 1/1?
• H2NCH2CH2NH2
• What is the limiting reagent if the actual mole ratio of
H2NCH2CH2NH2 / NiCl26H2O is 5/1?
• NiCl26H2O
LEWIS ACIDS AND LEWIS BASES
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Gilbert Lewis
A Lewis acid is an electron-pair acceptor.
A Lewis base is an electron-pair donor.
Which reactant is a Lewis acid?
Ni2+
Which reactant is a Lewis base?
COMPLEX IONS, LIGANDS, AND COORDINATION NUMBERS
• A complex ion is an ion that has a central metal
cation bonded (or coordinated) to 1 or more
groups of atoms. These groups of atoms are called ligands.
• Coordination number is the number of ligand atoms that bond to the
central metal of a complex ion.
• What is the metal atom in this complex ion?
• Ni2+
• What is the ligand?
• In fact, H2NCH2CH2NH2 is a bidentate ligand. Each H2NCH2CH2NH2 has
2 different atoms that bond to the central Ni2+.
• What is the coordination number for this complex ion?
• 6
COMPLEX IONS, LIGANDS, AND COORDINATION NUMBERS
• Name the ligand and coordination number for each of these
3 complex ions.
Ligand = Chloride, ClCoordination # = 2
Ligand = Ammonia, NH3
Coordination # = 4
• Are any of these ligands bidentate?
• No
Ligand = Water, H2O
Coordination # = 6
THE SYNTHESIS OF A COMPOUND USING A LIMITING REAGENT
• The purpose of this experiment is to identify the limiting
reagent for the following reaction:
NiCl26H2O(aq) + 3H2NCH2CH2NH2(aq)  [Ni(H2NCH2CH2NH2)3]Cl2(s) + 6H2O(l)
• How will you do this?
• Simply compare your experimental mole ratio of
H2NCH2CH2NH2 / NiCl26H2O with the theoretical mole ratio
of 3/1 for this reaction. If it is less than 3/1 then
H2NCH2CH2NH2 is the limiting reagent. If it is greater than
NiCl26H2O is the liming reagent.
3/1 then
• Once the limiting reagent is known, you can calculate the
theoretical yield of product ([Ni(H2NCH2CH2NH2)3]Cl2) and
the percent yield of product.
SAFETY
• Give at least 1 safety concern for the following procedures
that will be used in today’s experiment.
• Using NiCl26H2O, H2NCH2CH2NH2), and acetone
(CH3COCH3).
• These are irritants. Wear your goggles at all times.
Immediately clean all spills. If you do get either of these in
your eye, immediately flush with water.
• Acetone is extremely flammable. Never use it near a flame
or spark.
• Your laboratory manual has an extensive list of safety
procedures. Read and understand this section.
• Ask your instructor if you ever have any questions about
safety.
SOURCES
• McMurry, J., R.C. Fay. 2004. Chemistry, 4th ed. Upper
Saddle River, NJ: Prentice Hall.
• Park, J.L. 2004. ChemTeam: Photo Gallery Menu. Available:
http://dbhs.wvusd.k12.ca.us/webdocs/Gallery/GalleryMenu.
html [accessed 30 October 2006].
• Petrucci, R.H. 1985. General Chemistry Principles and
Modern Applications, 4th ed. New York, NY: Macmillan
Publishing Company.