chemistry report

Topics: Hydrogen, Hydrochloric acid, Titration Pages: 7 (842 words) Published: April 16, 2014

Abstract
The separation of a Fe3+ and Ni2+ mixture was firstly investigated; followed by the determination of the Fe3+ and Ni2+ content (concentration) in the original mixture. It was found that iron was a yellow solution and nickel respectively had a greenish colour. Their original concentrations respectively were 0.03669 M for iron and 0.03159 M for nickel. Introduction

Ion exchange materials are insoluble substances containing loosely held ions which are to be exchanged with other ions in solutions which come in contact with them. These exchanges take place without any physical alterations to be the ion exchange material. Ion exchangers are insoluble acids or bases which have salts which are insoluble, and this enables them to exchange either positively charged ions (cations exchanges) r negatively charged one (anion exchangers). Many natural substances such as proteins, cellulose, living cells and soil particles exhibit ion exchange properties which play an important role in the way they function in nature.

Synthetic ion exchange material based on coal and phenolic resin were first introduced for industrial use during the 1930s.

Results and Calculations
The concentration of Ni2+ and Fe3+ ions was to be calculated. In order to calculate the concentration of Ni2+ in the original test solution, we needed to do the double titration method. We do this in order to titrate the nickel from the test solution with EDTA then take the ratio of the volume EDTA to the volume Nickel. The recorded volumes were,

Table 1:
EDTA (mL)
Nickel (mL)
Ratio
22.00
32.1
0.685
28.0
41.6
0.673
33.7
42.3
0.797
35.7
43.9
0.813
36.9
46.4
0.795

The calculation for the determination of Ni2+:
The mole ratio of EDTA:Nickel is equal so,

This calculation was done with the first titration so if I take the average of the three best titrations with a difference of 3 out of 1000. Average EDTA =

Average Nickel =

[Ni] =

The nickel was transferred into the 100mL so the moles Ni2+ions can be calculated:

[Ni2+] =

In order to calculate the concentration of Fe3+ a single titration was used. We titrated the iron ionic solution with potassium dichromate until the endpoint was reached and found that the volume of potassium dichromate was 18.2mL.

1 mol Cr2O72- = 6 mol Fe2+

Discussion
The aim of this experiment was to separate a mixture of Ni2+ and Fe2+ ions by an ion exchange process using resin Amberlite IRA-400.

This experiment was split into two weeks. In the first week we had to separate Fe3+ and Ni2+ ions from Fe3+/Ni2+ test solution. This was done by preparing a resin column and running the Fe3+/Ni2+ test solution through the column with concentrated (11M) HCl. By adding concentrated HCl it separated the nickel from the solution which was greenish in colour. We then run the dilute (0.1M) HCl through the resin again. This resulted in the left over Fe3+ ions to come off the resin into a separate flask which was yellow in colour.

We left these solutions until the second week where we’d have to determine the concentration and iron in the original test solution. The nickel was determined by using the double burette titration method. EDTA was the solution used to titrate the nickel solution. The endpoint of this solution was the nickel solution turning purple. Accounting for human error during this long experiment, the accuracy of the titrations was not so precise. This resulted in us doing up to five titrations to get the ratios within the 3 out of a 1000 boundary. The iron was determined by a single titration by potassium dichromate. This was a difficult titration because there was no room for error as you could do this titration once and there were quite a few colour changes that needed to be observed until the endpoint, which was a blue-purple colour appeared.

The volumes were read off...


References: 1. Ion exchange resin. [Online]. Available: www.britannica.com/EBchecked/ topic/292829/ion-exchange-resin
2. Structure of EDTA. [Online]. Available. en.wikipedia.org/wiki/File:EDTA.svg
3. Structure of Murexide. [Online]. Available. en.wikipedia.org/wiki/File:Murexide.png
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