Docsity
Log inSign up
Docsity
Prepare for your exams
Prepare for your exams

Study with the several resources on Docsity

Earn points to download
Earn points to download

Earn points by helping other students or get them with a premium plan

Guidelines and tips
Guidelines and tips
Sell on Docsity
Sell on Docsity
Log inSign up

Prepare for your exams

Study with the several resources on Docsity

Find documents

Prepare for your exams with the study notes shared by other students like you on Docsity

Search Store documents

The best documents sold by students who completed their studies

Search through all study resources
Docsity AINEW

Summarize your documents, ask them questions, convert them into quizzes and concept maps

Explore questions

Clear up your doubts by reading the answers to questions asked by your fellow students

Earn points to download

Earn points by helping other students or get them with a premium plan

Share documents
download point icon20 Points

For each uploaded document

Answer questions
download point icon5 Points

For each given answer (max 1 per day)

All the ways to get free points
Get points immediately

Choose a premium plan with all the points you need

Study Opportunities

Choose your next study program

Get in touch with the best universities in the world. Search through thousands of universities and official partners

Community

Ask the community

Ask the community for help and clear up your study doubts

University Rankings

Discover the best universities in your country according to Docsity users

Free resources

Our save-the-student-ebooks!

Download our free guides on studying techniques, anxiety management strategies, and thesis advice from Docsity tutors

From our blog

Exams and Study
Go to the blog

Spectrophotometric analysis of copper, Lab Reports of Chemistry

Uta Mesivta of Kiryas JoelChemistry

Chem 112 – Experiment 2 – Simulation – Spectrophotometric Analysis of Copper .

Typology: Lab Reports

2021/2022

Uploaded on 01/21/2022

nicoth
nicoth 🇺🇸

4.3

(20)

262 documents

1 / 5

Toggle sidebar

This page cannot be seen from the preview

Don't miss anything!

bg1
Chem 112 – Experiment 2 – Simulation – Spectrophotometric Analysis of Copper
Background
General
An experiment that I always wanted to introduce into Chem 112 was “Synthesis of a Copper Coordination
Complex” however the subsequent analysis of the copper in the complex involved Spectrophotometric
Analysis, involving the use of a UV Spectrometry that the sheer size of the Chem 112 class and the cost of these
spectrometers precluded. Instead it was an experiment that was confined to Chem 121H.
This experiment involves some background theory that you may not meet in class and thus to facilitate
understanding this process I would like to introduce you to a former college of mine, Prof. William Vining who
has developed a beautiful introduction to this with some novel experiments and even a section that shows you
how you could potentially use a smart phone to make crude spectrophotometric analysis. This is just
background material for you and is not part of the laboratory report.
Spectroscopy
A solution appears colored because it absorbs certain wavelengths of light in the visible spectrum while
transmitting or reflecting others. The absorbance or transmission of light at specific wavelengths is measured
using spectrophotometry. Spectrophotometry data can be used to determine the concentration of a colored
substance in solution.
Spectrophotometry is a technique that measures the amount of light absorbed by a colored sample. The more
concentrated a colored substance in a solution is, the more light it absorbs. Therefore, this technique can be
used to analyze sample solutions of unknown concentration. The proportion of light that passes through a
solution is called transmittance, whereas the proportion of light that is absorbed is called absorbance. A
spectrophotometer is an instrument that quantitatively measures the proportion of light that passes through a
solution at different wavelengths. In a spectrophotometry experiment, the sample solution is contained in a
cuvette which is placed in the spectrophotometer. Light from a lamp is focused on the sample, and the light
transmitted through the sample is detected.
Transmittance is often expressed as a percentage and is calculated as shown below.
%T= (I/I0) × 100
where T : is transmittance.
I0 : is intensity of light received by solution.
I : is the amount of light transmitted by the substance.
Absorbance is related to transmittance by the equation below.
A = 2 – log10 T
pf3
pf4
pf5

Partial preview of the text

Download Spectrophotometric analysis of copper and more Lab Reports Chemistry in PDF only on Docsity!

Chem 112 – Experiment 2 – Simulation – Spectrophotometric Analysis of Copper

Background

General

An experiment that I always wanted to introduce into Chem 112 was “Synthesis of a Copper Coordination Complex” however the subsequent analysis of the copper in the complex involved Spectrophotometric Analysis, involving the use of a UV Spectrometry that the sheer size of the Chem 112 class and the cost of these spectrometers precluded. Instead it was an experiment that was confined to Chem 121H.

This experiment involves some background theory that you may not meet in class and thus to facilitate understanding this process I would like to introduce you to a former college of mine, Prof. William Vining who has developed a beautiful introduction to this with some novel experiments and even a section that shows you how you could potentially use a smart phone to make crude spectrophotometric analysis. This is just background material for you and is not part of the laboratory report.

Spectroscopy

A solution appears colored because it absorbs certain wavelengths of light in the visible spectrum while transmitting or reflecting others. The absorbance or transmission of light at specific wavelengths is measured using spectrophotometry. Spectrophotometry data can be used to determine the concentration of a colored substance in solution.

Spectrophotometry is a technique that measures the amount of light absorbed by a colored sample. The more concentrated a colored substance in a solution is, the more light it absorbs. Therefore, this technique can be used to analyze sample solutions of unknown concentration. The proportion of light that passes through a solution is called transmittance, whereas the proportion of light that is absorbed is called absorbance. A spectrophotometer is an instrument that quantitatively measures the proportion of light that passes through a solution at different wavelengths. In a spectrophotometry experiment, the sample solution is contained in a cuvette which is placed in the spectrophotometer. Light from a lamp is focused on the sample, and the light transmitted through the sample is detected.

Transmittance is often expressed as a percentage and is calculated as shown below.

%T= (I/I 0 ) × 100

where T : is transmittance. I 0 : is intensity of light received by solution. I : is the amount of light transmitted by the substance.

Absorbance is related to transmittance by the equation below.

A = 2 – log 10 T

where A : is absorbance. Based on the equation above, A has values between 0 and 2. Using a spectrophotometer, both %T and A can be measured.

Absorption Spectrum

The plot of the absorbance of a solution at a range of wavelengths is called an absorption spectrum. A colored solution will have one or more absorption maximum (λmax or lambda max) in the visible spectrum. Visible wavelengths cover a range from approximately 400 to 700 nm. The longest visible wavelength is red and the shortest is violet. The figure below illustrates this range as well as the absorption spectra of chlorophyll a and chlorophyll b.

Beer’s Law

Absorbance is related to concentration as defined by Beer’s law, shown below.

A = ϵcl

Where A: is the measured absorbance. ε: is the molar extinction coefficient in M –1^ cm –^. c: is the molar concentration in mol/L. l: is the path length in cm.

The molar extinction coefficient and path length are constant for a given substance and experimental setup. Therefore, if the absorbance of a standard solution with a known concentration is measured, an unknown concentration can be determined using the equation below.

Procedure

Experiment 2_1 – Determine the λmax of Colored Solutions.

  1. Take two cuvettes from the Containers shelf and place them on the workbench.
  2. Take 0.06 M copper(II) sulfate from the Materials shelf and add 3 mL to the first cuvette.
  3. Take 0.025 M cobalt(II) chloride from the Materials shelf and add 3 mL to the second cuvette.
  4. Take a spectrophotometer from the Instruments shelf and place it on the workbench.
  5. Place a third cuvette from the Containers shelf onto the workbench. Add 3 mL water to this cuvette. This is the blank cuvette.
  6. Insert the blank cuvette in the spectrophotometer. Make sure the spectrophotometer output is set to absorbance (A) and set the wavelength to 400 nm either by moving the slider or by clicking on the wavelength value and typing the new value. Press the Zero button. Remove the cuvette and place it on the workbench.
  7. Collect absorbance versus wavelength data for the copper(II) sulfate solution as follows: a. Move the cuvette with the 0.06 M copper(II) sulfate solution into the spectrophotometer. b. Record the absorbance for the solution. c. Increase the wavelength to 420 nm. Record the absorbance and corresponding wavelength. d. Continue increasing the wavelength in 20 nm increments and recording the absorbance at each setting until you reach 700 nm. e. Remove the cuvette from the spectrophotometer and place it on the workbench.
  8. Move the cuvette with the 0.06 M cobalt(II) chloride solution into the spectrophotometer and repeat the process in step 7 to measure the absorbance at each 20 nm increment. Remove the cuvette from the spectrophotometer and place it on the workbench.
  9. Clear the cuvettes from the bench by emptying them into the waste container and then dragging them to the sink.
  10. Review the absorbance data you collected for both copper(II) and cobalt(II) ions, and determine the wavelength at which the absorbance reading was the highest. This is your λmax (lambda max). Record the λmax value for both copper and cobalt ions. Note: If a well-defined peak does not exist it is acceptable to use the wavelength that corresponds to the highest measurable absorbance value.

Experiment 2_2 – Measure Absorbance versus Concentration for Cu 2+^ Ions.

  1. Take three clean 50 mL volumetric flasks from the Containers shelf and place them on workbench.
  2. Fill the flasks with the following amounts of 0.06 M copper(II) sulfate and 1 M nitric acid:

CuSO 4 (mL) HNO 3 (mL) Cu2+^ (M) Flask 1 20 20? Flask 2 15 5? Flask 3 10 0 0.

  1. Obtain 3 cuvettes from the Containers shelf. Transfer 3 mL from the first flask into the first cuvette , from the second flask into the second cuvette , and from the third flask into the third cuvette.
  2. Use the dilution formula, C 1 V 1 = C 2 V 2 , to calculate the concentration of Cu 2+^ ions in cuvettes 1 and 2. Record these concentrations. Use the table to record these concentrations.
  3. Obtain another cuvette from the Containers shelf and place it on the workbench. Add 3 mL water. This is the blank cuvette.
  4. Place the blank cuvette into the spectrophotometer. Check to make sure the spectrophotometer output is still absorbance (A). Set the wavelength to λmax for copper ions that you determined in the previous experiment. Press the Zero button.
  5. Remove the cuvette from the spectrophotometer and place it on the workbench. Insert the other three cuvettes in sequence , recording the absorbance each time. Be careful also to note which concentration of Cu2+^ ions is in each cuvette.
  6. Clear the cuvettes from the bench by emptying them in the waste then placing them in the sink.

Experiment 2_3 – Determine the Cu 2+^ Concentration in Unknown Solutions of Copper(II)Sulfate.

  1. Take three clean cuvettes from the Containers shelf and place them on the workbench.
  2. Take copper solution #1 from the Materials shelf and add 3 mL to the first cuvette.
  3. Take copper solution #2 from the Materials shelf and add 3 mL to the second cuvette.
  4. Add 3 mL water to the third cuvette as a blank.
  5. Insert the blank cuvette into the spectrophotometer. Make sure that the spectrophotometer is set to the wavelength corresponding to λmax for Cu2+^ ions.
  6. Press the Zero button. Remove this cuvette.
  7. Insert the next cuvette into the spectrophotometer and record the absorbance of the unknown solution. Repeat with the final cuvette.
  8. Clear the bench of all materials, containers, and instruments, then go to the General Chemistry web site and download the Data file , this when completed is the report that you send to your TA.