ADVANCE STUDY ASSIGNMENT Prelab Questions: complete the worksheet, show all work

Question

ADVANCE STUDY ASSIGNMENT
Prelab Questions: complete the worksheet, show all work

1. A student studied the clock reaction described in this experiment. She set up Reaction Mixture 2 by mixing
20. mL 0.010 M KI, 10. mL 0.001 M Na2S2O3, 10. mL 0.040 M KBrO3, and 10. mL 0.10 HCl using the
procedure given. It took about 45 seconds for the color to turn blue.

She found the concentrations of each reactant in the reacting mixture by realizing that the number of moles of
each reactant did not change when that reactant was mixed with the others, but that its concentration did. For any
reactant A,
No. moles A = MA stock x Vstock = MA mixture x Vmixture

The volume of the mixture was 50. mL. Revising the above equation, she obtained

MA mixture = MA stock x Vstock in mL/50. mL

Find the concentrations of each reactant by using the above equation.

[I-] = ____________ M; [BrO3-] = _____________ M; [H+] = ____________ M


a. What was the relative rate of reaction (1000/t)? _____________

b. Knowing the relative rate of reaction for Mixture 2 and the concentrations of I-, BrO3-, and H+ in that
mixture, she was able to set up Equation 5 for the relative rate of the reaction. The only quantities
that remained unknown were k, m, n, and p. Set up Equation 5 as she did, presuming she did it
properly. Equation 5 is on page 3.

Explanation / Answer

[I-] = 20 x0.01/50 = 0.004 M

[BrO3-] = ( 0.04x10)/50 = 0.008

[H+] = ( 0.1 x10)/50 = 0.02 M

a) relative rate = 1000/45 =22.22 s-1

b) relative rate = k'[I-]^m [BrO3-]^n[H+]^p

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