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Paper Chromatography Lab

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on 22 September 2014

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Transcript of Paper Chromatography Lab

Paper Chromatography Lab
By: Priyanka Das, Riju Patra and Tiffany Tang

To use paper chromatography to separate a mixture of metallic ions in solution, thus using the position and color of the spot produced by each ion to determine the ions present in the unknowns.


In this lab, samples of 5 different cations are placed on chromatography paper, along with a known mixture, which is a mixture of the 5 cations, and 4 unknown substances. The paper was then placed in eluting solution, which is a mixture of HCL, ethanol, and butanol, and then dried and stained with potassium iodide and potassium ferrocyanide.
Propagative Error
Propagative error is present in the Rf values, as incorrect distances measured led to incorrect calculations. The lack of reliability reduces the accuracy of the results. This also influences final average calculated for the Rf value of a cation.
Determinate Error
The main source of error was not making each dot of solution, on the paper, dense enough before allowing the dots to diffuse across the paper. When applying the ions, if too much is used, it could lead to bleeding through in the paper. Furthermore, using too less could lead to difficulty in observation. There was also a risk of cross contamination in the capillary tubes.
Advanced Studies Assignment
1. Rf values= Distance moved by compound / Distance move by solvent

Indeterminate Error
There are always variables beyond human control that can affect the data such as room temperature, possible contamination of chemicals used and other factors.
Hydrochloric Acid
Synonym- none
Chemical Formula-HCl
Personal Protection- Face shield, full suit, vapor respirator. Be sure to use an approved+certified respirator or equivalent. Gloves. Boots.
Stability- The product is stable.
Toxicology- Classified 3 (Not classifiable for humans) by IPAC. May cause damage to the following organs: Kidney, liver, mucous membranes, upper respiratory tract, skin, eyes, circulatory system, teeth. Hazardous in case of eye contact (corrosive), of inhalation (lung corrosive).

Synonym- none
Chemical Formula-C2H6O
Personal Protection- Wear protective eyeglasses or chemical safety goggles as described by OSHA’s eye and face protection regulations. Wear appropriate gloves to prevent skin exposure. A respiratory protection program that meets regulations.
Stability- Stable under normal pressure and temperature.
Toxicology- Not listed

Synonym- none
Chemical Formula-C4H9OH
Personal Protection- Splash goggles. Lab coat. Vapor respirator. Be sure to use an approved + certified respirator or equivalent. Gloves.
Stability- The product is stable.
Toxicology- Hazardous in case of skin contact (irritant, permeator) of ingestion, of inhalation, slightly hazardous in case of skin contact (sensitizer)

Silver Nitrate
Synonyms- none
Chemical Formula- AgNO3
Product is stable under normal conditions. This substance is toxic to lungs mucous membranes. Slightly hazardous in case of skin contact, ingestion, inhalation. Wear full face shield, full suit, gloves and boots.

Cobalt Nitrate Hexahydrate
Synonyms- none
Chemical Formula- Co(NO3)2
This product is stable. Avoid reducing agents, moisture, excessive heat and combustible materials. Hazardous in case of skin contact, ingestion, inhalation. Wear goggles, respirator and gloves.

Cupric Nitrate trihydrate
Synonyms- copper (II) Nitrate trihydrate; Nitric acid copper (2+) salt
Chemical Formula-Cu(NO3)2
Reactive with reducing agents, combustible materials, organic materials and metals. Hazardous in case of skin contact, ingestion and inhalation. Wear goggles, lab coat, respirator and gloves.

Ferric Nitrate Nonahydrate
Synonyms- none
Chemical Formula- Fe(NO3)3
Avoid strong oxidizing agents, reducing agents, light, combustible materials and high temperatures. Extremely hazardous in case of skin contact, hazardous in case of ingesting, very hazardous in case of inhalation wear goggles, lab coat, respirator and gloves.

Mercuric Nitrate Monohydrate
Synonyms: nitric acid mercury (2+) salt
Chemical Formula: Hg(NO3)2
Avoid high temperatures, light, reducing agents, cyanides and nitrogen oxides. Extremely hazardous in case of ingestion, skin contact and inhalation.

Potassium Ferricyanide
Synonym: Potassium Hexacyanoferrate (III)
Chemical Formula: K2(CrO4)
Avoid heat, light and acids. Hazardous in case of skin contact, ingestion and inhalation. wear goggles, lab coat and respirator.

Potassium Iodide
Synonyms: none
Chemical Formula:KI
Avoid light, moisture and long exposure to air. Reactive with oxidizing agents, organic materials, metals and acids. Slightly hazardous in case of skin contact ingestion and inhalation. Wear goggles, lab coat and gloves.

R(f1)= 1.2cm / 8.1cm =.15cm
Standard Deviation
Discussion of Theory
Averaged the values of each cation
Used SD to figure out how off each average was from each other in terms of preciseness

S^2= Σ(xi - xm)^2/ (n-1)

Ex: 3
Standard Deviation of Ag+
S2 = ((-0.0612)^2 + (-0.0639)^2 + (-0.0503)^2 + (-0.0639)^2 + (-0.0707)^2)/(5-4) = 0.0697
0.0775 +/- 0.0697

Standard Deviation Values:
Co 2+=
0.358 +/- 0.0338
Cu 2+=
0.446 +/- 0.0318
Fe 3+=
0.630 +/- 0.0457
Hg 2+=
0.982 +/- 0.0294
Discussion of Theory cont.
The hypothesis of this experiment is that due to the nature of each cation’s physical properties, each ion will diffuse at a different rate via paper chromatography; thus, mixtures of multiple ions can be separated into their components through this method. To use this method, one must know the possible cations of the mixture.
The calculations of this lab give us the calculated Rf value for each cation used in the mixture. This calculation shows the distance the cation moved in relation to the distance the solvent moved. By using determined precise Rf values, a specific cation can be identified. Rf values are greater when the cation moves a greater distance, and visa versa.

The purpose of this lab was fulfilled because each mixture was separated and Rf values were determined.
Due to different substances having different solubilities, as the solvent moves across the paper by capillary action, the components begin to separate into diffuse zones.
After the solvent rises up the paper, and the paper is dried and then sprayed with a staining reagent. The staining reagent reacts with the ions, and reveals a different color for each ion.

Discussion of Theory cont.
Calculations show how because each cation retains different properties, some cations such as Hg +2 were able to travel till the solvent front while other cations such as Ag +1 barely travel past the initial line
Paper chromatography is not only useful in separating mixtures into pure substances, but also allows chemists to identify substances in an unknown mixture.
Real Life Application: Paper chromatography is used in all fields such as detecting alcohol in blood samples to detecting traces of lead in drinking water.

2. Samples can often be separated into their components by chromatography because as a solvent passes through a solid, it pushes the components of of a mixture with it (solubility affects rate).

3. Since the paper is longer than 4.0cm, it is crucial that the solvent be allowed the appropriate time to move the maximum distance. The longer the solvent runs up the paper, the more the compounds will separate. Therefore, by only allowing the solvent to move 4.0 cm, the separation of ions will be limited and the results, inaccurate.

R(f2) = 3.2cm/8.1cm= .40cm
R(f3)= 5.0cm/8.1cm= .62cm
R(f4)= 7.0cm/ 8.1cm= .86cm
4. 6 micro liters x 1 L x 6gCu(2+) x 10^6 micro grams =36 micro grams of Cu(2+) ions
10^6 micro liters
Rf = D/L = Distance cation moves/Distance solvent moves

Co 2+ = 2.90 cm D/L = 2.90 cm/ 7.35 cm = 0.395
Solvent = 7.35 cm

Average Rf Values:

Ex: 2
Rf Values for Ag+
Unknown #1- 0.0163
Unknown #2- N/A
Unknown #3- 0.0272
Unknown #4- 0.00680
Known- 0.0136
Ag+ (control)- 0.0136
Average Rf Value of Ag+
xm= 0.0163+ 0.0272+ 0.00680+ 0.0136+ 0.0136 / 5 = 0.0775

Average Rf Values:
Co 2+ = 0.358
Cu 2+ = 0.446
Fe 3+ = 0.630
Hg 2+ = 0.982

Indeterminate errors are error that can be minimized but never eliminated. They arise from uncertainties in measurement and other factors and are random.
Determinate error are controllable errors whose cause can be determined and thus, eliminated.
It can be concluded from this experiment that paper chromatography and Rf values are valid ways of separating and identifying cations within an unknown mixture.
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