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Section Name Experiment 21 Advance Study Assignment: Rates of Chemical Reactions, II. A Clock Reaction 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 0.0001 M Na.S.0. 10 mL 0.040 M KBrO and 10 ml, O.10 M HCT using the procedure given. It took about 45 seconds for the color to turn bluc. She found the concentrations of cach reactant in the reacting mixture by realizing that the number of moles of cach reactant did not change when that reactant was mixed with the others, but that its con- centration did. For any reactant A. a xV -M no. moles A M, The volume of the mixture was 50 ml. Revising the above equation, she obtained V(ml) x M, M. 50 ml IMacia mixtune Find the concentrations of cach reactant by using the above equation. M M: (H) M: (BrO,)= (I)= b. What was the relative rate of the reaction (1000/n? c. Knowing the relative rate of reaction for Mixture 2 and the concentrations of I. BrO., 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 172. 2. For Reaction Mixture 1 the student found that 85 seconds were required. On dividing Equation 5 for Reaction Mixture 1 by Equation 5 for Reaction Mixture 2, and after canceling out the common terms (, terms in (BrO,) and (H"), she got the following equaticn: 0.0020) -G 11.8 Recognizing that 11.8/22 is about equal to %. she obtained an approximate value for m. What was that value? By taking logarithms of both sides of the equation, she got an exact value for m. What was that value? Since orders of reactions are often integers, she reported her approximate value as the order of the reac- tion with respect to I Advance Study Assignment: Rates of Chemical Reactions, II. A Clock Reaction 1. A student studied the clock reaction described in this experiment. She set up Reaction Mixture 2 by mixing 20 mlL 0.010 M KI, 10 mL. 0.001 M Na,S,O, 10 ml. 0.040 M KBrO, and 10 ml. 0.10 M HCI 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 cach reactant did not change when that reactant was mixed with the others, but that its con- centration did. For any reactant A a. no. moles A = M, xV M A stock A mixture The volume of the mixture was 50 ml. Revising the above equation, she obtained V (mL) 50 mL M, = M..X A wak A mixture Find the concentrations of each reactant by using the above equation. (I) M; (BrO,) M; (H) b. What was the relative rate of the reaction (1000/)? c. Knowing the relative rate of reaction for Mixture 2 and the concentrations of I, BrO., 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 172. 2. For Reaction Mixture 1 the student found that 85 seconds were required. On dividing Equation 5 for Reaction Mixture 1 by Equation 5 for Reaction Mixture 2, and after canceling out the common terms (, terms in (BrO,) and (H')), she got the following equation: 0,0020) 0.0040 -GT 11.8 22 Recognizing that 11.8/22 is about equal to 2, she obtained an approximate value for m. What was that value? m By taking logarithms of both sides of the equation, she got an exact value for m. What was that value? m Since orders of reactions are often integers, she reported her approximate value as the order of the reac- tion with respect to I

Answer 1

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HeSre kI(aa) Concentaation r Concentration Potassium iodide the P9oblem Fhom given volume iodide in in Concentaation and The and o m Solution stock is O.O1om Vetocl) M atuhe) Cstock) V(mxtue) xaoni O-O10M Wohoo.0 omi Con centnatin mix tune is 00o4oM didide Potassium bnomate CkBr03) strong electrolyte is The onic nation +Br 0 Cag) Completely into potassium Ton Br03 dissociated kBro3 is Bro mate and

and volume Concentration obhomate The ion in the stock So lution Ooo m oml an d baomate The Con Centaatiom Veto ck) M Br o Cm) V&mi tune) 0 b40x loml o 0086 m Soml o 0og m mix tuse bro mate Com centsahion he Volume and Con Centaation The lom and O.1o m Solution the in on centhation The C X (S) H Cm) Vem) z O.o62 m mix ture O002m H C centaation The Yate Relative t - b 22S

HT Se la tive Yate ons Bro3 C C CBro" (H")f Re lative ate the Concentsatiom of Values Substitute Hydeogen ion ion and io dide ion bromate Eq uation above in kCT CBro° (k*)f Rate Re lative 22S