Experiment 10:碘鐘實驗(II)－Shawn910018的部落格

Experiment date: 2013/12/27

Principle:

Rate of reaction can be show as Rate = K[A]^x[B]^y. And then the order of reaction should be x & y, rate constant is a stationary value.

This experiment is trying to find the rate formula between S₂O₈^2- and I^- and use S₂O₃^2- to notice the time. I₂ and S₂O₃^2- can be reaction in a high speed that can even see I₂ as I^-. And when S₂O₃^2- is gone, I^-and I₂ will become I₃^-and the liquid will become dark blue.

We can find the order of reaction by change a single object’s concentration and see the reaction rate’s change.

Activation energy is defined as the minimum energy required to start a chemical reaction.

Catalysis make the reaction start with less free energy required, but the total energy from reactants to products does not change. A catalyst may join in multiple chemical transformations, but the same time it won’t reduce after the reaction.

Chemicals and their Properties:

Na₂S₂O₃ (CAS 7772-98-7):	158.09774 g/mol d:1.84g/cm³ mp: 48.3 °C
K₂S₂O₈ (CAS 7727-21-1 ):	270.322 g/mol 2.477 g/cm³ mp: <100°C (Decomposition)
NaCl (CAS 7647-14-5):	58.44277g/mol 2.16 g/cm³ mp:801°C bp:1465°C
K₂SO₄ (CAS 7778-80-5):	174.259 g/mol (without water) 2.66g/cm³ (without water)
NaI (CAS 7681-82-5):	149.89 g/mol 3.67 g/cm³ mp:660°C bp:1304°C
CuSO₄(CAS 7758-98-7):	159.608 g/mol (without water) 3.603 g/cm³

Tools:

1. Pasteur pipette (10mL/25mL)

2. Timer

3. Cork

4. Erlenmeyer flask

5. Polystyrene bowl

6. Ice

Safety and Waste Disposal:

Safety : Always wear your coat, gloves and eye protection.

Procedure:

This experiment is fallow the last one.

Part. A

Prepare 10 Erlenmeyer flask (50mL) and get the Order of reaction.
Put the right amount of Na₂S₂O₃NaCl NaI in the Erlenmeyer flask.
Take 5mL K₂SO₄ and put in the Erlenmeyer flask.

Part. B

Fallow Part. A
Put some ice and water in a polystyrene bowl.
Put Erlenmeyer flask in and wait for few minutes. When the temperature is balance, add 5mL 0.15 M K₂S₂O₈. Shake it and start the timer.
change the Polystyrene bowl with ice and water into water about 40°C and do it again.
Compare the time you get with others.

Part. C

Fallow Part. A
Add 2 drops of CuSO₄ and then add 5mL 0.15 M K₂S₂O₈.
Shake it at the same time and start the timer.
Compare the time you get with others.

Results:

part A
1	Before	After	1	Before	After
0.008497	17	19.3	0.008477	15.5	18.7
2	Before	After	2	Before	After
0.006453	17	19.3	8:42.9	15.5	18.7
3	Before	After	3	Before	After
0.004558	17	18.6	0.004306	15.5	18
4	Before	After	4	Before	After
0.003527	17	19	0.003612	15.5	18.5
5	Before	After	5	Before	After
0.001783	17	18.2	0.001813	15.5	18.3
6	Before	After	6	Before	After
0.000673	17	18.5	0.000597	15.5	18.4
part B			Part C
1			1	56.81
59.34		35C	2	59.23
2
55.42		40C		KI	1.0004
3				K2S2O8	0.15
44.34		45C		Na2S2O3	0.1934
4				Time	Sec
29.85		50C		temp	^oC

Analysis

Part A

	[A]	ln[A]	1/[A]	t
1	0.081823	-2.5032	12.22149	733.3
2	0.066946	-2.70387	14.93738	528.15
3	0.052069	-2.95518	19.2052	383
4	0.037192	-3.29165	26.88728	308.35
5	0.022315	-3.80248	44.81213	155.35
6	0.007438	-4.90109	134.4364	54.9

[A]-T

ln[A]-t

1/[A]-t

Part B

	r	k	lnK	1/T
1	0.000188	0.000188	-8.57891	0.016852
2	0.000201	0.000201	-8.51057	0.018044
3	0.000252	0.000252	-8.28751	0.022553
4	0.000374	0.000374	-7.89181	0.033501
	m	0.0244	Ea	-0.20286

Discussion:

The first one took a lot of time to wait, maybe we really need more timer to make the experiment go faster. And the last one is definitely the opposite situation.

50 seconds makes us even have to focus on it while shaking. The second part is a little bit hard to control the temperature at the designated number, cause the heater can't be thermostatic. But the third experiment is successfully for us to see the speed of reaction become faster.

References:

The first one took a lot of time to wait, maybe we really need more timer to make the experiment go faster. And the last one is definitely the opposite situation. 50 seconds makes us even have to focus on it while shaking. The second part is a little bit hard to control the temperature at the designated number, cause the heater can't be thermostatic. But the third experiment is successfully for us to see the speed of reaction become faster.

Reflection and Feedback:

The hardest part I think is not the experiment but the calculate. The K of the second experiment will change every time so Excal really helps me a lot. this is good to see I finally finish the report cause the calculate in my Excal is really massy that I need time to figure out what the number means. next time I'll try to make it look more ordered.