Chem lab practicum
If you plot the concentration of crystal violet vs time and get a negative linear slope, what is the expected order of the reaction in [crystal violet]
0th order
What size volumetric flask will you use to then make your collected solution to a known volume? exp 2
100.0 mL
What is the molar ratio between Ca2+ and EDTA
1:1
If you plot the natural log of the concentration of crystal violet vs time on a graph and get a negative linear slope, what is the expected order of the reaction in [crystal violet]
1st order
How many acidic hydrogens does neutral Eriochrome black t indicator have
2
If you perform cation-exchange chromatography on a solution contains Mg2+ ions, how many moles of H+ ions will be displaced by 1 mole Mg2+
2
what will be the pH of the three solutions you will use (8)
2.0, 7.0, 11.0
You are trying to titrate to neutralization 10.00 mL of a .2 M monoprotic acid using 0.1 M sodium hydroxide and phenolphthalein as an indicator. About how much NaOH do you expect it to take?
20.00 mL of NaOH
If you perform cation-ion exchange chromatography on a solution containing Fe ions, how many moles of H+ ions will be displaced by 1 mole Fe
3
In this weeks Ka experiment spectrophotometric analysis is being used. What is the range wavelength that you will need your solutions over
350 nm to 700 nm
How many acidic hydrogens does neutral EDTA have
4
What is the expected max wavelength range for a solution that is yellow in color
425-450
What would be the expected conductivity of Tap water
554
what is the expected max wavelength range for a solution that is blue
600-650 nm
What is the molar ration S2O3 with respect to IO3
6:1
what would be the expected conductivity of DI water
7
Which of these solutions will make it possible to determine H2O (8)
7.0; the buffered solution
How will you determine the Absorbance in order to solve the above equation? (8)
ABS vs wavelength of all three solutions
To make a calibration curve of a series of dilution what do you need to plot?
Absorbance vs concentraion
What are the two things that was plotted in exp 9
Absorbance vs wavelength
What mobile phase will be used in Part 1 of the TLC separation
Acetone, 50:50 acetone pet ether; 20:80 acetone pet ether
What does the term Ka mean
Acid dissociation constant
After your sample of Ca2+ water is passed through the resin what type of analysis will be done? (exp 2)
Acid/base titration or volumetric analysis
What was the lewis acid in exp 2
Ca2+
What are example of Lewis acids that we have used in lab so far
Ca2+, Ni3+, Cu2+
What is the observed color change when you use phenolphthalein as an indicator when titrating with a base
Colorless -> pink
What would you expect the color change to be if we used phenolphthalein as our indicator when NaOH is added to our H+ solution
Colorless -> pink
What two metals are you analyzing in exp 3
Cu and Ni
Give the definition of Rf (retention factor) for the TLC separations
Distance the spot travels, distance the mobile phase travels
What is the defining characteristic of a lewis acid
Electron pair acceptor
What is the defining characteristic of a lewis base
Electron pair donor
Look up other types of chromatography and list them
Gas chromatography; gel electrophoresis; HPLC
How are these types of chromatography different from the two types you are using?
Gas is the mobile phase for GC; electricity is mobile phase for electrophoresis; high pressure liquid chromatography is used under pressure
After adding 20.00 ml of Ca2+ water solution to a column that has cation-exchange resin in it. What would you expect to be the eluate in this separation
H+
what is the HOMO in terms of MO theory
Highest occupied molecular orbital
Why do you only want to use a pencil to mark your TLC plates
Inks can be dissolved and travel with mobile phase
What does it mean if a ligand is bidentate
It has two donor atoms and can bind to the central metal ion at two points
A cation ion-exchange column is not regenerated after being used. How might this affect the Ca2+ determination for the next set of students
It is possible that not enough H+ remains on the column to exchange with all of the Ca2+ in the next students sample and the calculated concentration of Ca2+ would be lower than the actual
what is the primary standard used for the redox titration
KIO3
what are the units of the molar absorptivity constant in the kinetics experiment
L/mol x cm
What is the LUMO in the terms of MO theory
Lowest occupied molecular orbital
What does each symbol represent in the q = mC(delta)T
Mass (g), change in temperature,
What was the secondary standard used for the redox titration
Na2S2O3
What is the standard used in your exp 2 analysis
NaOH
If you perform anion-exchange chromatography on a solution contains Cl ions, what will be your eluate
OH-
If you perform ion-exchange chromatography, with anion-exchange resin, on a solution containing Cl-ions what ions will be in your eluate
OH-
What indicator did you use in the ion-exchange chromatography
Phenolphthalein
What is the indicator used in exp 2 analysis
Phenolphthalein
What fundamental process is the separation based on for both of these types of chromatography
Polarity
what color change do you see when you add NaOH to crystal violet
Purple -> colorless
If there are three protons on a carbon atom adjacent to a CH2 group, what would you expect the splitting/multiplicity of the CH2 group to be
Quartet
What is the observed color change when you use Eriochrome Black T as an indicator
Red -> blue
List the compounds (dyes) you will use for the TLC separations
Rhodamine B, Erthrosin B, Sudan black B
What stationary phase is used for your column chromatography separations?
Silica
You are doing an acid-base titration and phenolphthalein is your indicator, where should acid and base be
The base should be in the buret, the acid should be in flask
If you cool the solutions of both NAOH and crystal violet below room temperature, how would you expect the rate of color change to be compared with the rate using room temperature solutions
The color change will occur more slowly
if all the HCl was not properly rinsed out of the cation-exchange column, how would that effect the concentration of Ca2+
The concentration of Ca2+ would appear to be higher
What would happen if you added the starch too early in the redox titration
The starch-I3 complex would not be able to react with the thiosulfate and un-complex and the solution would not turn colorless
If the solution turns red when using the Eriochrome Black T as your indicator what does that mean?
There are metal ions in the solution
If the solution turns blue when using eriochrome black t as your indicator, what does that mean
There aren't any metal ions present
If the solution turns blue when using eriochrome black t as your indicator what does that mean? (1)
There aren't metal ions that would bind with eriochrome black t
If the solution turns red when using eriochrome black t as your indicator what does that mean
There is Ca2+ and Mg ions present
When regenerating the cation ion-exchange column, you add an excess of HCl. If the column is not rinsed enough to remove any excess H+ how would this affect the calculated Ca2+ moles of the next group
There would be an excess of H+ along with the H+ from the Ca2+ added to the column resulting in a higher calculated result then actual
What types of chromatography will you be performing in this experiment
Thin layer and column
What is the purpose of adding the buffer solution to the Ca2+ solution
To deprotionate the acidic hydrogens in the EDTA so they can bind to Ca2+
What were the techniques used in last week's lab (exp 2)
Volumetric analysis and chromatography
What data will you be measuring and recording in this experiment (8)
absorbance at different wavelengths
When is the pKa = pH
at the 1/2 equivalence point
what are the colors of bromothymol blue in basic and acidic conditions
blue and yellow
What indicator will you be analyzing? (8)
bromothymol blue
What type of ion-exchange will you be performing (exp 2)
cation-ion exchange
If the reaction between a metal ion and a ligand gave off heat what would be the expected sign of delta H be and is the reaction endothermic or exothermic
delta H negative, exothermic
What is the slope of the Beer's Law calibration curve equal to
e x l
What are examples of Lewis bases that we have used in lab so far
eriochrome black t, EDTA, ethylenediamine
In the thermochemistry lab what should your final units be
kJ x mol-1 of metal ion
What is the color of phenolphthalein in basic conditions
magenta
List the compounds (dyes) used for the column chromatography
methylene blue, fluoresessin
What is the indicatory used in the potentiometric titration
phenolpthalein
What indicator will you use in the redox titration
starch
What are the two phases that each type of chromatography have?
stationary and mobile phase
What is the purpose of the indicator in a titration
to find the moles of an unknown by seeing the endpoint of a reaction
The reaction between metal ions and ligands is an example of a lewis acid-base reaction
true