1. Write the rate law for the reaction between HCl and Na 2 S 2 O 3 . 2. Using t
ID: 878696 • Letter: 1
Question
1. Write the rate law for the reaction between HCl and Na2S2O3.
2. Using the rate law that you determined for the reaction, predict the rate of the reaction if the concentration of HCl was changed to 0.8M and the concentration of Na2S2O3is 0.12M.
# of drops
# of drops
# of drops
Stock Solution
Stock Solution
Reaction (after mixing in well)
Reaction (after mixing in well)
Reaction Time
(seconds)
Reaction
Rate
(sec-1)
HCl
H2O
Na2S2O3
HCl
Na2S2O3
HCl
Na2S2O3
Trial 1
Trial 2
Average
8
0
12
1M
0.3M
.4
.18
26.6
27.9
27.3
.04
8
6
6
1M
0.3M
.4
.09
64.4
60.9
62.7
.02
8
8
4
1M
0.3M
.4
.06
87.3
82.6
84.9
.01
# of drops
# of drops
# of drops
Stock Solution
Stock Solution
Reaction (after mixing in well)
Reaction (after mixing in well)
Reaction Time
(seconds)
Reaction
Rate
(sec-1)
HCl
H2O
Na2S2O3
HCl
Na2S2O3
HCl
Na2S2O3
Trial 1
Trial 2
Average
12
0
8
1M
0.3M
.6
.12
33.7
32.3
33
.03
6
6
8
1M
0.3M
.3
.12
42.6
39
40.8
.02
4
8
8
1M
0.3M
.2
.12
62.9
55.4
59.2
.017
# of drops
# of drops
# of drops
Stock Solution
Stock Solution
Reaction (after mixing in well)
Reaction (after mixing in well)
Reaction Time
(seconds)
Reaction
Rate
(sec-1)
HCl
H2O
Na2S2O3
HCl
Na2S2O3
HCl
Na2S2O3
Trial 1
Trial 2
Average
8
0
12
1M
0.3M
.4
.18
26.6
27.9
27.3
.04
8
6
6
1M
0.3M
.4
.09
64.4
60.9
62.7
.02
8
8
4
1M
0.3M
.4
.06
87.3
82.6
84.9
.01
Explanation / Answer
Order with respect to Na2S2O3
r1 = k (0.4)x(0.18)y --------(1)
r2 = k(0.4)x(0.09)y --------(2)
Equation 1/Equation 2 = r1/r2 = (0.4)x(0.18)y/(0.4)x(0.09)y = (0.18)x/(0.09)x =
2 = 2y
y= 1
Order with respect to HCl
r3 = k (0.6)x(0.12)y ----------(3)
r4 = k(0.3)x(0.12)y -----------(4)
Equation 3/Equation 4 = r3/r4 = (0.6)x(0.12)y/(0.3)x(0.12)y = (0.6)x/(0.3)x =
1.5 = 2x
x = 0.585
Rate law of the reaction, rate = k[HCl]0.585[Na2S2O3]1
Rate constant k = rate/[HCl]0.585[Na2S2O3]1
= 0.03/(0.60.585 x 0.12) = 0.337
Rate of the reaction if the concentration of HCl was changed to 0.8M and the concentration of Na2S2O3 is 0.12M
Rate = k[HCl]0.585[Na2S2O3]1
= 0.337 x (0.8)0.585(0.12)1
=0.0355/s
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