Experiment 1
Name : Nour RIZK 20207095
I.
Reaction mixture composition
Acetone
mL
Exp. 1
Exp. 2
Exp. 3
10
20
10
I2
mL
10
10
10
HCl
mL
H2O
mL
10
10
20
20
10
10
Time needed for
the color of I2 to
disappear
1 min 34 s
49 s
50 s
Determination of reaction orders with respect to acetone, I2, and H+
II.
Exp. 1
Exp. 2
Exp. 3
[Acetone]ₒ
[I2]ₒ
0.8
1 x 10-3
1.6
1 x 10-3
0.8
1 x 10-3
[H+]ₒ
0.4
0.2
0.2
Reaction rate
1.06 x 10-5
2.04 x 10-5
2 x 10-5
[Acetone]ₒ= (V (acetone) x [acetone]) : total volume
Total volume = 50 ml
R=−(𝐼(𝑓𝑖𝑛𝑎𝑙) − 𝐼(𝑖𝑛𝑖𝑡𝑖𝑎𝑙)) ∶ 𝛥𝑡
(Reaction rate = [I2]ₒ : Time needed for the color of I2 to disappear
Questions
1. Determine the order of the reaction with respect to acetone (m).
R=k[A]m[I2]n[H+]p ; n=0 so
R=k[A]m [H+]p
R1=1.06 x 10-5 mol/L /s
R2 = 2.04 x 10-5 mol/L /s
𝑹𝟐
𝑹𝟏
=
𝐤[𝟐𝟎]𝐦 [𝟏𝟎]𝐩
𝒌[𝟏𝟎]𝒎 [𝟏𝟎]𝒑
= 2m
1
𝑹𝟐
𝑹𝟏
= (2.04 x 10-5) : (1.06 x 10-5) = 2 (approx.)
m=1
2. Determine the order of the reaction with respect to H+ (p).
R=k[A]m[I2]n[H+]p ; n=0 so
R=k[A]m [H+]p
𝑹𝟑
𝑹𝟏
𝑹𝟑
𝑹𝟏
=
𝐤[𝟏𝟎]𝐦 [𝟐𝟎]𝐩
𝒌[𝟏𝟎]𝒎 [𝟏𝟎]𝒑
=2p
= (2 x 10-5 ) : (1.06 x 10-5) = 2 (approximately )
p=1
3. Determine the rate law of the reaction.
R=k[A]1[I2]0[H+]1
4. Calculate the rate constant k.
In the 1st reaction, R= 1.06 x 10-5 M/s
[A] = 0.8 M
[H+] = 0.4 M
So, k= 3.3125 x 10-5 M-1s-1
Experiment 2
Recorded voltage: 0.016 V
1. What is the role of a salt bridge?
Salt bridge maintains electrical neutrality in two compartments by allowing movement of
anions towards anodic compartments and cations towards cathodic compartments. It helps
in maintaining the change balance in two half cells.
2
2. Calculate the standard cell potential for the constructed cell (E°Cu2+/Cu= 0.34V). Compare the
calculated cell potential to the measured voltage of your electrochemical cell. Calculate %
error and describe the possible sources of error.
Cu2+ + 2e- --> Cu Eo = 0.340V
Ecell = E0cell - (
Ecell = 0.378 V
𝟎.𝟎𝟓𝟗𝟏
𝟐
) log(0.05 : 1)
0.378 V > 0.016 V
So the calculated cell potential is bigger than the voltage measured.
(0.016 : 0.378 ) x 100 = 4.23 %
The possible sources of error are:
 The cause of the voltage drops can be the actual electrical resistances in
the circuits.
 An error in the voltmeter may also occur if its input impedance (resistance)
is low where it becomes part of the circuit and gives false readings.
 Beakers are not cleaned well
 Pressure, temperature and the concentrations of the ions can also have an
effect.
 Inaccuracy of the scale (volume).
3