calculate the initial molarity of Kl, Na2S2O3, and (NH4)2S2O3 in the solution fo
ID: 845812 • Letter: C
Question
calculate the initial molarity of Kl, Na2S2O3, and (NH4)2S2O3 in the solution for rach of the four trials.
Monitoring the initial rate of this reaction will involve a bit of trickery. As can be seen in the above reaction, I2 is one of the products. We will add a small amount of another chemical, this sulfate ion (S2O32), to convert the I2 to 1-.I2 + 2 S2O32- rightarrow 2 I- + S4O62- When the small amount of thiosulfate ion is used up, the I2 produced in the first reaction will form a complex ion with another iodide ion and a starch molecule to form a blue complex. The color change will be immediate and dramatic. I- + I2 + starch rightarrow I3- (starch) (blue compels) At this point, the time is recorded and an additional amount of thiosulfate is added. The solution will turn colorless, then after a period of time, will change into the blue color again.Explanation / Answer
In the table volume unit is not mentioned so assuming it as mL
N1V1=N2V2
N1=Concn of stock
V1=Volume taken
N2=Concn of working solution
V2=Volume of working solution
Trial-1
Total volume=100mL
A)KI
0.2M X25=N2X100
=>N2=(25X0.2)/100=0.05 M
B)Na2S2O3
0.2 X 1ml=N2X100 =>N2=2mM
C)(NH4)2S2O3
0.2 X 25=N2 X 100 =>N2=0.05 M
Trial 2
Total volume=
A)KI
25 X2 =N2 X 100 =>N2=0.05 M
B)Na2S2O3
0.2 X 1=N2X 100 =>N2= 2mM
C)(NH4)2S2O3
0.2 X 50=N2 X 100 =>N2=0.1 M
Trail 3
Total volume =100 ml
A)KI
0.2 X 50=N2 X100 =>N2=0.1 M
B)Na2S2O3
0.2 X 1=N2X 100 =>N2= 2mM
C)(NH4)2S2O3
0.2 X 25=N2 X 100 =>N2=0.05 M
Trial 4
Total volume=100mL
A)KI
0.2 X 12.5=N2 X100 =>N2=0.025 M
B)Na2S2O3
0.2 X 1=N2X 100 =>N2= 2mM
C)(NH4)2S2O3
0.2 X 50=N2 X 100 =>N2=0.1 M
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