To Determine the Content of Iron in Iron Tablets by Titration

PROCEDURES:

Making a solution of the tablets

1. 5 iron tablets were weighed accurately, and then dissolved in about 100cm3 of 1.0 moldm-3 sulphuric acid in a conical flask. Some heating was required, but not more than the necessary needed to dissolve the tablets.

2. The mixture was filtered into a beaker, making sure that no solution was lost, then the conical flask was washed out with water and the washings were poured through the filter.

3. Finally, distilled water was poured over the residue and these washings we collected as well.

The filtrate was then poured into a 250cm3 standard volumetric flask, washing out the beaker and adding washings to the standard flask. The mark was made up using distilled water.

Titration with Potassium Manganate (VII)

1. Using a pipette (safety) filler, 25cm3 of the iron (II) solution was pipette from the volumetric flask into a conical flask.

2. About 25cm3 of 1.0 moldm-3 sulphuric acid was added and titrated with 0.01 moldm-3 Potassium Manganate (VII) solution.

3. The experiment was repeated until two coincident results were obtained.

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OBSERVATIONS, RESULTS, DATA:

Description

Initial Reading

Final Reading

Volume of HCl

Rough

0

12.5

12.5

First Titration

12.5

23.2

11.3

Second Titration

23.2

35.2

12.0

Average

7.5

15.3

7.7

TABLE SHOWING RESULTS OF IRON TABLET SOLUTION AND POTASSIUM MANGANATE (VII) TITRATION

CALCULATIONS:

To calculate the amount of iron dissolved in volumetric flask

Iron + sulphuric acid --> iron sulphate + hydrogen gas

Fe(s) + H2SO4(aq) --> FeSO4(aq) + H2(g)

Concerned with 1 mole of iron sulphate produced from 1 mole sulphuric acid

# of moles of H2SO4 = volume/1000 X concentration

= 100/1000 X 1.0

= 0.1 mol of H2SO4

1 mole iron sulphate produced from 1 mole sulphuric acid

x 0.1

hence x = 0.1 mol

volume of solution = 100cm3

volume of solution with water = 250cm3

dilution = 250/100 = 25

# of moles of FeSO4 = 0.1 x 25

= 2.5 moles of FeSO4 (original amount)

To calculate the amount of iron left over after titration

Iron + sulphuric acid --> iron sulphate + hydrogen gas

Fe(s) + H2SO4(aq) --> FeSO4(aq) + H2(g)

Concerned with

DISCUSSION:

CONCLUSION: The percentage of 2-ethanoylhydroxybenzoic acid (acetylsalicylic acid) in aspirin tablets was found to be 51.3%. The hydrolysis of aspirin tablets was also successfully completed by using sodium hydroxide base. The conclusions drawn are not as accurate as expected due to the high difference in percentage of acetylsalicylic acid content found compared to that given.

Analyzing Iron Tablets

Assessment: (M/M)

Mark Scheme

Weighing

- Zero before weighing [1]

Heating

- Use of proper attire (apron/goggles)

- Heat slowly

- readjusting flame to proper height/color

(any 2 - 1 mark; all 3 - 2 marks)

Measuring Volume

- Measuring Cylinder: On a flat Surface

read bottom of meniscus [1]

- Volumetric flask: fill to the mark [1]

Pipette: Rinse with required solution [1]

Touch top of pipette to surface liquid [1]

Proper use of pipette filler [1]

- Burette: rinse with required solution

Use funnel to fill burette

Nozzle free of air bubbles.

(any 3- 1 mark; any 4- all 2 marks)