Chemistry Lab Report

Topics: Titration, Mole, Erlenmeyer flask Pages: 6 (1802 words) Published: March 6, 2013
ab reportChemistry 117L Laboratory Report

Name: Aneesa Noorani Lab Day: Tuesday Lab Room: SCL 114 Date of Experiment: January 22, 2013TA: Mikhail

1. Basic Laboratory Skills

Purpose(s) of the Experiment: The purpose of the first part of today’s experiment is to establish the stoichiometry of the reaction between titrate oxalate (C2O42-) and permanganate (MnO4-). The purpose of the second part of today’s experiment is to learn about the concepts of the rate of chemical reactions and homogenous catalysis.

Broad Overview of the Experimental Method: The purpose of the first part of today’s experiment will be accomplished by performing titrations. A solution with C2O4- of known concentration will be titrated with MnO4-. The second purpose will be accomplished by: timing and observing the reaction that takes place in a tartrate-H2O solution when the solution has Co2+ added as a catalyst.

Results and Calculations

Part 1: Reagents and their concentrations used

[MnO4-] in the standardized solution provided = 0.025 mol L-1

[H2SO4] used = 2 mol L-1

Initial mass of (vial + sodium oxalate) = 7.8680 g
Mass of (vial + Na2C2O4) after initial transferring of some Na2C2O4 to beaker = 6.9537 g Mass of Na2C2O4 used = 0.9143 g

Volume of standard sodium oxalate solution prepared = 100 mL = 0.100 L

[C2O42-] in the standard solution prepared:

Work: [C2O42-] = Mass of Na2C2O4 used
Molar Mass of Na2C2O4 x Volume (in L) of the standard solution
= 0.9143 g
133.99882 g mol-1 x 0.100 L
= 6.82 x 10-2 mol L-1

Table 1: Titration Data

Titration #| Volume of Standard Na2C2O4 solution used (mL)| Initial Buret Reading (mL)| Final Buret Reading (mL)| Volume of MnO4- solution used (mL)| 1| 10.00| 9.70| 20.60| 10.90|
2| 10.00| 20.60| 31.50| 10.90|
3| 10.00| 31.60| 42.50| 10.90|
Table 2: Mole ratio calculations

Titration #| Moles of Oxalate Pipetted| Moles of Permanganate Used| ExperimentalMoles of OxalateMoles of Permanganate| Smallest integer oxalate to permanganate mole ratio| 1| 6.82 x 10-4 mol| 2.725 x 10-4 mol| 6.82 x 10-4 mol2.725 x 10-4 mol| 5/2| 2| 6.82 x 10-4 mol| 2.725 x 10-4 mol| 6.82 x 10-4 mol2.725 x 10-4 mol| 5/2| 3| 6.82 x 10-4 mol| 2.725 x 10-4 mol| 6.82 x 10-4 mol2.725 x 10-4 mol| 5/2|

Sample Calculations:
Moles of oxalate pipetted:
10.00 mL = 0.0100 L
0.0100 L x 6.82 x 10-2 mol L-1
= 6.82 x 10-4 mol

Moles of permanganate needed:
10.90 mL = .01090 L
.01090 L x 0.025 mol L-1
= 2.725 x 10-4 mol

Smallest integer oxalate to permanganate mole ratio:
6.82 x 10-4 mol = 5
2.725 x 10-4 mol 2

Balanced reaction between oxalate and permanganate:
5 C2O42- (aq) + 2 MnO4- (aq) + __ H+ (aq) --> 10 CO2 (g) + 2 Mn2+ (aq) + ____ H2O (l)

To figure out z, the coefficient in front of H+, you must simply balance the reaction. Since there are 28 oxygen molecules on the reactant side and only 20 on the product side, the coefficient in front of the H2O must be 8. This makes the number of hydrogen molecules equal to 16 on the product side, therefore the coefficient in front of the H+ must be 16. The balanced reaction is:

5 C2O42- (aq) + 2 MnO4- (aq) + 16 H+ (aq) --> 10 CO2 (g) + 2 Mn2+ (aq) + 8 H2O (l)

Part 2: The Co2+ catalyzed tartrate – hydrogen peroxide reaction
For the 1 mL reaction, the solution started out a light pink and then turned into a brown color with an orange tinge. At around 3 minutes the solution began bubbling and looked like ginger ale. Then, the solution turned yellowish and there was much more bubbling and fizzing at 4 minutes. The solution turned green around 5 minutes and then a deeper green at 6 minutes. The solution continued to fizz and bubbles gathered around the edges. At around 7 minutes you could begin to feel the solution getting much hotter because it was releasing heat. It also turned a very bright green. At 8 minutes and 30 seconds, the solution...
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