Complete a Formal Report- Copper Ammine

Synthesis and Analysis of A Copper Ammine ComplexPart II: Standardization of Hydrochloric Acid
Objectives:
•
•
To utilize the techniques involved in standardizing solutions.
To standardize a solution of hydrochloric acid for use in analyzing the copper ammine
coordination complex made previously
Introduction:
The process used to determine the concentration of a solution with high accuracy is called
standardizing a solution. To standardize an unknown solution, you react that solution with
another solution of accurately known concentration.
In this experiment, we will be standardizing hydrochloric acid with anhydrous sodium
carbonate. This reaction takes place in two stages:
Na2CO3(aq) + HCl(aq) → NaHCO3(aq) + NaCl(aq)
(1)
NaHCO3(aq) + HCl(aq) → NaCl(aq) + CO2(g) + H2O(l)
(2)
This means that the complete reaction is as follows:
Na2CO3(aq) + 2 HCl(aq) → 2 NaCl(aq) + CO2(g) + H2O(l)
(3)
Each stage uses a separate indicator. Phenolphthalein is used in stage 1 and methyl orange is
used in stage 2. This gives you the experience of using two different indicators (phenolphthalein
color change is easy to see, the methyl orange is a bit more difficult).
Procedure:
1. Calculate the approximate amount of anhydrous sodium carbonate needed to
completely react with 20 mL of 1.0 M hydrochloric acid.
2. Clean a buret by rinsing with several portions of tap water. The rinse water may be
poured down the drain.
3. Obtain about 175-200 mL of the hydrochloric acid solution in a plastic bottle that is on
the front table. You will use this solution for week 2 and week 3. Please be sure to label
the bottle. Keep your bottle in your blue bin for week 3.
4. Rinse the buret with three portions (about 3 mL each) of the HCl solution. Drain each
HCl rinse and discard into the waste container located in the hood.
5. Fill the buret with HCl to slightly above the zero mark and clamp the buret up vertically.
6. Remove air bubbles from the tip of the buret by draining the HCl into a small beaker.
Read the HCl level to within ±0.02 mL and record this value. (It is not necessary to have
the HCl level at exactly the 0.00 mL mark. Anywhere below 0.00 mL will suffice. What is
important, is to record this initial HCl reading to two decimal places.)
7. Measure approximately the mass of sodium carbonate calculated in step one on a tared
weighing boat and transfer it to a clean, labeled Erlenmeyer flask. Similarly prep a
second sample, recording the masses for each. Dissolve the sodium carbonate in about
50 mL of R.O. water and add 2 drops of phenolphthalein.
8. Titrate by slowly adding hydrochloric acid solution to the first carbonate sample. Swirl
the flask after each addition. The end-point of the titration is when the solution just
changes from pink to colorless.
9. Note the volume on the buret, then add 2-3 drops of methyl orange to the same
Erlenmeyer flask.
10. Titrate with the hydrochloric acid. The end-point of this titration is when the solution
just changes from yellow to red. Note the second volume reading.
11. Repeat steps 8-10 with the second Erlenmeyer flask.
12. Calculate the molar concentration of the HCl solution. The molar concentration from the
FOUR analyses (2 from phenolphthalein and 2 from methyl orange) should be within
±1%.
Synthesis and Analysis of a Copper Ammine Complex
Part I: Synthesis
Objectives
1) Assemble a table of amounts for a synthesis.
2) Synthesize a coordination compound.
3) Analyze amounts of metal and ligand in order to find a formula.
Introduction
During this lab period you will synthesize the copper complex,
xCu2+ + yNH3 ⇋ [Cux(NH3)y]2+,
the following week you will standardize a hydrochloric acid solution, and the following period
you will quantitatively determine the Cu/NH3 mole ratio in your product.
When the solid, CuS04 • 5H20, dissolves and a square planar complex is formed with water as the
ligand (a molecule or ion that covalently bonds to the central metal). When ammonia is added, it
replaces the water in the structure:
The complex, [Cux(NH3)y]2+, is surrounded by water molecules and prevented from combining
with sulfate ion SO42-, which is also in the solution. Ethanol is added to pull the water away from
the ions by hydrogen bonding to the water and the precipitate, [Cux(NH3)y]SO4, forms.
Pre-Lab
Write the overview, outline the procedure, and make an amounts table in your lab
notebook.
Procedure
Part I: Preparation of Copper-Ammine Complex
Using a balance to weigh a 250 mL beaker, zero the balance and add about 12 g of copper (II)
sulfate pentahydrate, CuSO4 • 5H20, record the weight. Crush the bigger lumps as small as
possible with your spatula. The smaller the particles of CuSO4 • 5H2O, the easier it will be to
dissolve the solid. Add 24 mL of distilled water to the beaker, and stir until no more of the solid
dissolves. Place the beaker under a hood, and slowly add 100-mL of 6 M aqueous ammonia, NH3,
with vigorous stirring. (CAUTION: Concentrated aqueous ammonia causes burns on your skin.
Wear gloves when handling it. If any spills or spatters occur onto your skin rinse the affected
area thoroughly with water.) After all ammonia has been added and stirred, all material should be
in solution. Cool the solution for 5 minutes in an ice bath, but be careful that no water from the
ice bath gets into your beaker. Slowly add with stirring 50 mL of 50% ethanol, C2H5OH. As the
ethanol is added, a fine blue precipitate should form. If no precipitate is observed, add 10 mL
more of ethanol. After the addition of ethanol is complete, maintain the solution in the ice bath
for 10 additional minutes. Filter the mixture using vacuum filtration through a Buchner funnel.
After the solution has been filtered, continue the suction on the solid for an additional 5 to 10
minutes in order to dry the solid as much as possible. Disconnect the vacuum line from the filter
flask, turn off the water, and remove the funnel from the flask.
Transfer the precipitate to a previously weighed 250-mL beaker and write your initials on the side
of the beaker. You will analyze your product (Part III) during another lab period and determine
the yield of your product.
Formal Report- Copper Ammine
Abstract
_________________/5
The abstract summarizes four essential aspects of the report: the purpose of the
experiment, key findings, significance, and major conclusions. The abstract should
be one paragraph of 100-200 words.
Introduction
_________________/10
The introduction describes the experiment that has been done in the context of
other experiments or processes. Include why the experiment is important and link it
to common practices. Include material of your choosing (from at least 7 journal
sources) that is relevant to the topic and justifies the importance of the given
experiment. Your report must include the reaction.
Experimental
_________________/10
Describe the procedure in your own words. This should not have been copied from
the lab handout. Set off individual experimental portions with a title that is
underlined (ex. Synthesis of copper oxalate). Include your table of amounts in this
section.
Results and Discussion
________________/15
Describe the results from each experiment. Generate appropriate tables and figures.
Tables need to be numbered and have a title at the top of the table (Table 1:
appropriate title). Figures need to be numbered and have a title at the bottom of the
figure (Figure 1: appropriate title). Drawings of compounds will need to be included
in this section.
Conclusion
_______________/10
Summarize results of all experiments. Include percent yield. Mention in some detail
each experiment and results arising from each experiment. Add additional insight in
to your experimental results.