Lab 5- Quantative Analysis

Lab #5:   Quantitative Analysis- Redox Titrations

Aim:
To determine the percent of iron in an iron (II) sulfate.

Introduction:
Redox reactions are those in which electrons move from one reactant to another reactant. These types of reaction can also be called oxidative-reduction reactions. A most common example of such types of reactions is corrosion. During these reactions, when an atom loses electrons it is referred to as oxidation and when atoms gain electrons it is referred to as reduction. In this example we deal with redox reactions and eventually for this equation, I2(aq) + 2 S2O32-(aq) → S4O62-(aq) + 2 I ‾(aq), the iodine (I2) is reduced to iodide (I-) and the thiosulfate is oxidized to tetrathionate ion. The equation above is an example of redox reaction due to the movement of electrons from on reactant to another.

You are provided with:

a pipet and   suction bulb
a buret and stand
Erlenmeyer flasks
A beaker
Measuring cylinder
Funnel
Distilled (deionized) water
Medicine Dropper
Sulfuric acid

S:   1.39 g/100 mL aqueous solution iron (II) compound
T:   0.02M Potassium permanganate

Procedure:
1. Rinse the buret and pipet with distilled water.
2. Rinse the pipet with a small quantity of iron(II) solution   (approx . 5 mL)
3. Pipet 25.0 mL of S and place into an Erlenmeyer flask.
4. Using a measuring cylinder add 10 mL H2SO4.    
5. Rinse the buret with a small quantity of T (KMnO4, approx. 5 mL)
6. Titrate the content of the flask with T to the colorimetric endpoint
7. Record your titration results in the table below.
8. Repeat the titration to achieve accurate results.

Results of Titration
| Rough | Trial 1 | Trial 2 |
Final buret   reading/mL | 12.5 | 25.3 | 28.0 |
Initial   buret   reading/mL | 0 | 12.5 | 25.2 |
Volume of T used /mL | 12.5 | 12.8 | 12.8 |

DATA TABLE
| Trial 1 | Trial 2 |
Mass of   Iron compound | 0.3475 g | 0.3475 g |
Molarity of KMnO4 | 0.02 M | 0.02 M |
Volume KMnO4 | 12.8 mL |...