Download Report 2 to hand in

WINTER 2017
CHEMISTRY 230 LABORATORY
REPORT FOR EXPERIMENT 2
Name:_____________________________Lab Day: _________________________
DATA (Print Data sheet and attach to front of Report)
A. ROASTING
Mass of Malachite: ___________ g
Description of Malachite and Characterization
(include conductivity and malleability)
Mass of CuO produced ___________ g
Description of CuO
B. Reduction
Mass of Cu produced: _____________g
Description of Cu and Characterization (include conductivity and malleability)
C. Production of CO2
Mass of Malachite: __________g
Mass of beaker: ___________ g
Mass of beaker + HCl: _________ g
Mass of Beaker, Malachite, and HCl after reaction: _____________g
C. % Copper by Colorimetry
Mass of CuSO4•5H2O: ____________ g dissolved in dilute NH3 (aq) to _____________ mL
Standard Solution 1 Concentration: ______________M
Absorbance (650nm):________________
Standard Solution 2 Concentration: ______________M
Absorbance (650nm):________________
Standard Solution 3 Concentration: ______________M
Absorbance (650nm):________________
Standard Solution 4 Concentration: ______________M
Absorbance (650nm):________________
Standard Solution 5 Concentration: ______________M
Absorbance (650nm):________________
Absorbance of Dissolved Malachite and diluted in 100 mL flask (from C4): _________________________
Questions. Answer on Looseleaf, Attach to Report
1.
a)
Re-write the balanced reaction equations for the Roasting and Reduction steps and clearly
indicate what is being oxidized and what is being reduced.
(Use must state the oxidation numbers of each element to show this.)
+1 -2
0
+1 -2 +1
0
eg.
2.
2 H2O (l)
+ 2 Na (s)
6
2 NaOH (aq) + H2 (g)
a) Show an example calculation for how you determined the concentrations of your standard solutions.
(in the % Copper by Colorimetry part)
b) using a spreadsheet program make a graph of your standard curve. (include the best fit straight line
and the R2 value on your graph).
Properly describe and label this graph, being descriptive of what the graph is about and
the conditions the data was taken at. The description should stand alone, I should not
have to look at the procedure to figure out what is going on. Think about these questions
when giving a descriptive title.
*What chemicals are involved (for example, what is the solvent)?
*What specific compound, or ion am I measuring?
* What wavelength of light was used?
* Is the temperature or pressure important?
* What are the units?
c)
“A copper ore deposit is a localized zone in the earth’s crust that contains copper-bearing
minerals in unusually large quantities. On average, the continental crust contains about 0.0058
percent copper, or 58 parts per million. A deposit of copper-bearing minerals is classed as an ore
reserve if there are sufficient quantities and concentrations of minerals to be extracted at a profit.
Commercial copper ore deposits today contain from 0.5 to 6 percent copper, or between 100 and
1000 times the crustal average.”
ci) From your spectrophotometer tests and standard curve, calculate the percent copper by mass
in your sample of malachite. In other words, how many grams of copper per 100g of malachite.
(Show your work, use your line of best fit from the graph to help answer this.)
cii) How many times greater is the percentage of copper in your sample compared to the earth’s
crustal average of copper?
3.
Use your data from C4 on pg 12 of the manual to answer a) and b). Assume that the mass lost from your
malachite upon digestion with HCl is due to loss of CO2 gas which comes from the carbonate ion.
a) How many moles of CO2 were released from the malachite sample?
b) If every mole of CO2 released came from a carbonate ion - what is the mass percent of carbonate in
your sample? In other words, for every 100 g of malachite sample, how many grams appear to be
carbonate?
Use your data from A1 and B4 to answer c) and d)
c) How many moles of Copper were recovered from the malachite sample (from end of Part B)?
d) Assuming that you recovered all the copper from your sample in the form of copper metal (from end
of Part B) - what is the mass percent of copper in your sample (g of copper per 100g Malachite)?
e) If the malachite samples we used were pure Cu2(OH)2CO3 - what should the mass percentage of
copper be in the sample?
f) If the malachite samples we used were pure Cu2(OH)2CO3 - what should the mass percentage of
carbonate be in the sample?
4.
Inorganic compounds often are highly colored and in this weeks lab, it has to do with d orbitals. When
copper (II) ions are complexed with a ligand (such as NH3 in the complex Cu(NH3)42+) the energy levels
of the 3d orbitals are split.
In a higher level inorganic chemistry class,
it can be explained further why the d
orbitals split with different energy levels.
To explain how this gives a color, let’s use
Titanium as an example.
Ti has the electron configuration of:
[Ar] 3d2 4s2
As the Ti3+, it loses 3e-s and therefore has the electron configuration: [Ar] 3d1
When the Ti3+ is complexed (such as Ti(H2O)63+), the d orbitals split. In ground state
it would look like this.
If a sample of Ti(H2O)63+ is illuminated with white light, light energy of a specific
energy (wavelength) can be absorbed and the electron can jump to an excited state.
The light energy absorbed depends on the ªE between the split d-orbitals. In this
case light of a blue-green color (ªE) gets absorbed and the light reflected back to
your eyes from the solution will therefore appear violet.
a) What is the electron configuration of Cu?
b) What is the electron configuration of Cu2+?
c) Fill in a table (left) of Cu2+ in its ground state for the 3d orbital when it is
complexed with ammonia.
d) Fill in a table (left) of Cu2+ in an excited state when it is complexed with ammonia.
e) The Cu(NH3)42+ appears blue. What color of light is being absorbed by this
solution?