Experiment 3 - PHYSICAL CHEMISTRY PDF

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EXPERIMENT 3Order of ReactionObjectiveTo determine the order of a reaction. MethodThree burettes were set up, one was contained KMnO 4 (0), one with H 2 C 2 O 4 (0) and one with distilled water. A label was placed on each. It was difficult to visually differentiate between water and oxalic acid. The...

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EXPERIMENT 3 Order of Reaction

Objective To determine the order of a reaction. Method Three burettes were set up, one was contained KMnO 4 (~0.02M), one with H 2C2O4 (~0.5M) and one with distilled water. A label was placed on each. It was difficult to visually differentiate between water and oxalic acid. The exact molarities of the KMnO 4 and H 2C2O4 were recorded. Into a thoroughly washed and dried conical flask, the required amount of H2C2O4 and water (if any) were placed according to Table 4.1. The amounts were dictated by the experiment that was doing. If overshoot, started again. This lab was very dependent on dispensed the exact quantities. The required amount of KMnO4 was placed into a test tube. The permanganate was added to the oxalic acid and the timing was started when have emptied the permanganate tube. The solution was mixed thoroughly by swirling the conical flask and continued to swirl until the solution have turned into light yellow/brown colour. The timing was stopped and the time it actually took for the reaction to take place was recorded. Repeated this with a second and third trial. The average of these three was took as the reaction time. Steps 3 through 5 was repeated for Experiments 2 and 3. The rate for each of the three experiments were determine. This was just [KMnO 4]/average. The values of k, x and y were determined. The full rate equation for the reaction was wrote out. Note that Rate = k[KMnO4]x[H2C2O4]y. Table 4.1: Volume of reagents required Reagents H2C2O4 KMnO4 H 2O

Results

Expt 1 cm3 20.00 10.00 0.00

Expt 2 cm3 20.00 5.00 5.00

Expt 3 cm3 10.00 10.00 10.00

Exp

Volume(mL) 0.5M H2C2O4

0.02M KMnO4

H 2O

1

20

10

2

20

5

3

10

10

Molarity(M) Total

0.5M H2C2O4

0.02M KMnO4

0

30

0.3333

5

30

10

30

Time(s) 1

2

3

Ave

6.6667×10-3

220

215

210

215

0.3330

3.3333×10-3

216

230

232

226

0.1667

-3

336

405

523

421

6.6667×10

Calculation Experiment 1

[H2C2O4] (M) 0.3333

[KMnO4] (M) 6.6667×10-3

2

0.3330

3.3333×10-3

Rate (Ms-1) [ KMnO 4 ] Rate 1= t1 6.6667 × 10−3 M ¿ 215 s = 3.1008 × 10-5Ms-1 Rate 2=

[ KMnO 4 ]

t2 3.3333 ×10−3 M ¿ 226 s = 1.4749 × 10-5Ms-1

3

0.1667

6.6667×10-3

Rate 3=

[ KMnO 4 ]

t1 6.6667 × 10−3 M ¿ 421 s = 1.5835 × 10-5Ms-1

Rate = k[KMnO4]x[H2C2O4]y

Determining of k, x and y So, to determine x, H2C2O4 must be constant so compare experiment 1 and experiment 2: x

y

Rate 1 k [ KMnO 4 ] [ H 2C 2 O 4 ] = Rate 2 k [ KMnO 4 ] x [ H 2C 2 O 4 ] y x

3.1008 ×10−5 Ms −1 k [ 6.6667 ×10−3 ] [ 0.3333] = x −5 1.4749 ×10 Ms −1 k [ 3.3333 ×10−3 ] [ 0.3333] y y

2.1024 = 2.0000x log 2.1024 = log 2.0000x log 2.1024 = x x=

log 2.0000

log 2.1024 log 2.0000

x=1.0720 x=1

To determine y,

[ KMnO 4 ] must be constant so compare experiment 1 and experiment 2: x

y

Rate 1 k [ KMnO 4 ] [ H 2C 2 O 4 ] = Rate 2 k [ KMnO 4 ] x [ H 2C 2 O 4 ] y −3 x

−5 3.1008 ×10 Ms−1 k [ 6.6667 × 10 ] [ 0.3333] = x −5 1.5835 ×10 Ms−1 k [ 6.6667 ×10−3 ] [ 0.1667] y

1.9582 = 1.9994y log 1.9582 = log 1.9994y log 1.9582 = y y=

log 1.9994

log1.9582 log 1.9994

y=0.9699

y=1 

Rate = k[KMnO4]1[H2C2O4]1

y

Determine K from experiment 2: 1.4749

× 10-5Ms-1 = K[3.3333×10-3]1[0.3333]1 K = 0.0133M-1S-1

The rate law is; Rate = 0.0133 M-1S-1[KMnO4] [H2C2O4] 

Therefore, this is second order reaction.

Conclusion In conclusion, the order of a reaction was determined which is the rate law is; Rate = 0.0133 M 1 -1

S [KMnO4] [H2C2O4]. Therefore, the order of a reaction is second order.

References Mashiah Domat Shaharudin, Nesamalar kantasamy, Introduction to Physical Chemistry Laboratory Manual, Order of Reaction Mickey, C. D. (1980). Chemical Kinetics: Reaction Rates. Journal of Chemical Education, 57(9), 659. https://doi.org/10.1021/ed057p659 https://www.chemguide.co.uk/physical/basicrates/orders.html...