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Typical results are shown for the absorbance of [ Ti ( H 2 O ) 6 ] 3 + size 12{ \[ "Ti" \( H rSub { size 8{2} } O \) rSub { size 8{6} } \] rSup { size 8{3+{}} } } {} measured at 490 nm.

Concentration (mg/mL) %Transmittance Absorbance
0 100. 0
1 50.0 0.301
2 25.0 0.602
3 12.5 0.903

Over the studied range the solutions obey Beer's Law. If a solution has a measured absorbance of 0.450, we can calculate its concentration to be 1.5 mg/mL.

Experimental procedure

In this experiment, each lab pair will measure the absorbance of CuSO 4 size 12{"CuSO" rSub { size 8{4} } } {} at six concentrations. You will create a calibration curve to correlate copper sulfate concentration to absorbance. This curve will be used next week to determine the concentration of an unknown copper sulfate solution and, in turn, the percent yield of a series of chemical reactions.

Materials CuSO 4 5H 2 O size 12{"CuSO" rSub { size 8{4} } cdot "5H" rSub { size 8{2} } O} {} distilled water pipette bulb 1cm cuvette 4 - 25 mL volumetric flask for your dilutions

Note: You will be borrowing these and must collect them from your TA. Do not forget to return the flask at the end of the lab). All students will lose 3 points in that lab section if any go missing!

100 mL volumetric flask for the parent solution (in your drawer)10 mL volumetric pipette or 10 mL graduated cylinder

  • Measure out an appropriate mass of CuSO 4 5H 2 O size 12{"CuSO" rSub { size 8{4} } cdot "5H" rSub { size 8{2} } O} {} to get 100ml of ~0.1M solution and record the mass on your report form. Show your calculation to the TA before making the solution. This is your parent solution. Calculate the molarity using the actual mass measured and record it.
  • Do the following dilutions and calculate the concentrations for each.
Dilution (ml parent : ml total)
0:25 (DI H 2 O size 12{H rSub { size 8{2} } O} {} )
5:25
10:25
15:25
20:25
25:25 (parent solution)
  • Measure the absorbance of the 6 solutions you have prepared and the unknown given to you by your TA.

Analysis

Plot the concentration as a function of absorbance for your six solutions. Perform a linear regression analysis and determine the equation of a best-fit line.

Prelab: spectrophotometry and data analysis–Beer’S law

Hopefully here for the Pre-Lab

Name(Print then sign): ___________________________________________________

Lab Day: ___________________Section: ________TA__________________________

This assignment must be completed individually and turned in to your TA at the beginning of lab. You will not be allowed to begin the lab until you have completed this assignment.

In many of the experiments that you will do throughout the duration of this course you will be asked to analyze your data by making plots and calculating the best fit line through your data. One program commonly used to analyze data in this fashion is Microsoft Excel®. The following exercise will help you through the process used to obtain a plot and linear regression for a set of data.

Suppose you go for a 5 mile run and you tabulate the after each mile as in the following table.

Distance Traveled (miles) Time (sec)
1 510
2 1026
3 1548
4 2077
5 2612

Questions:

  • Plot the distance traveled in miles vs. the time in seconds.
  • Use linear regression to obtain a trendline and give the equation obtained in terms of the variables distance traveled and time and the R-squared value. Comment on the meaning of the R-squared value and its significance when doing data analysis.
  • Using the equation you obtained by doing linear regression, estimate how long the 6th mile will take you to run.
  • Assuming this linear trend persists, how far have you run if you finish in 2900 sec.

EXCEL INSTRUCTIONS:

  • In order to plot this data in excel, you should enter the data exactly as above in to column A (rows 1-6) and column B (rows 1-6).
  • To plot the data you will need to go to Insert on the tool bar and then click Chart. A Chart Wizard will appear. Select XY(Scatter) as the Chart type and choose the sub-type that does not have any lines connecting the points, then click next.
  • On Step 2, click on the series tab near the top of the screen and click Add.
  • You do not need to name the series unless you have multiple plots on one graph, but you can type in a name if you wish.
  • To insert the X data, click on the icon at the far left of the x series box.
  • Select the x values by clicking on the first one and while the left mouse button is down dragging the mouse down to the last value.
  • When the values have been selected click the icon again and repeat for the y values. You may also manually enter the values by separating them with a comma. Don’t forget you need to remember what units you are using when answering questions.
  • Click next when you have x and y values entered correctly.
  • The next step is just entering title information and changing the appearance of your plot; click next when finished.
  • Choose your chart location and then finish. You now need to place a linear regression line on your plot.
  • Right click on a data point and pick add trendline.
  • Choose linear as the type and click the options tab.
  • Check the boxes to get the equation and R-squared value and click ok.

Questions & Answers

can someone help me with some logarithmic and exponential equations.
Jeffrey Reply
sure. what is your question?
ninjadapaul
20/(×-6^2)
Salomon
okay, so you have 6 raised to the power of 2. what is that part of your answer
ninjadapaul
I don't understand what the A with approx sign and the boxed x mean
ninjadapaul
it think it's written 20/(X-6)^2 so it's 20 divided by X-6 squared
Salomon
I'm not sure why it wrote it the other way
Salomon
I got X =-6
Salomon
ok. so take the square root of both sides, now you have plus or minus the square root of 20= x-6
ninjadapaul
oops. ignore that.
ninjadapaul
so you not have an equal sign anywhere in the original equation?
ninjadapaul
Commplementary angles
Idrissa Reply
hello
Sherica
im all ears I need to learn
Sherica
right! what he said ⤴⤴⤴
Tamia
what is a good calculator for all algebra; would a Casio fx 260 work with all algebra equations? please name the cheapest, thanks.
Kevin Reply
a perfect square v²+2v+_
Dearan Reply
kkk nice
Abdirahman Reply
algebra 2 Inequalities:If equation 2 = 0 it is an open set?
Kim Reply
or infinite solutions?
Kim
The answer is neither. The function, 2 = 0 cannot exist. Hence, the function is undefined.
Al
y=10×
Embra Reply
if |A| not equal to 0 and order of A is n prove that adj (adj A = |A|
Nancy Reply
rolling four fair dice and getting an even number an all four dice
ramon Reply
Kristine 2*2*2=8
Bridget Reply
Differences Between Laspeyres and Paasche Indices
Emedobi Reply
No. 7x -4y is simplified from 4x + (3y + 3x) -7y
Mary Reply
is it 3×y ?
Joan Reply
J, combine like terms 7x-4y
Bridget Reply
im not good at math so would this help me
Rachael Reply
yes
Asali
I'm not good at math so would you help me
Samantha
what is the problem that i will help you to self with?
Asali
how do you translate this in Algebraic Expressions
linda Reply
Need to simplify the expresin. 3/7 (x+y)-1/7 (x-1)=
Crystal Reply
. After 3 months on a diet, Lisa had lost 12% of her original weight. She lost 21 pounds. What was Lisa's original weight?
Chris Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
China
Cied
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
Porter
many many of nanotubes
Porter
what is the k.e before it land
Yasmin
what is the function of carbon nanotubes?
Cesar
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
Sravani Reply
what is system testing?
AMJAD
preparation of nanomaterial
Victor Reply
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
Himanshu Reply
good afternoon madam
AMJAD
what is system testing
AMJAD
what is the application of nanotechnology?
Stotaw
In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
Azam
anybody can imagine what will be happen after 100 years from now in nano tech world
Prasenjit
after 100 year this will be not nanotechnology maybe this technology name will be change . maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
Azam
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
Prasenjit
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
Damian
silver nanoparticles could handle the job?
Damian
not now but maybe in future only AgNP maybe any other nanomaterials
Azam
can nanotechnology change the direction of the face of the world
Prasenjit Reply
At high concentrations (>0.01 M), the relation between absorptivity coefficient and absorbance is no longer linear. This is due to the electrostatic interactions between the quantum dots in close proximity. If the concentration of the solution is high, another effect that is seen is the scattering of light from the large number of quantum dots. This assumption only works at low concentrations of the analyte. Presence of stray light.
Ali Reply
the Beer law works very well for dilute solutions but fails for very high concentrations. why?
bamidele Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Honors chemistry lab fall. OpenStax CNX. Nov 15, 2007 Download for free at http://cnx.org/content/col10456/1.16
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