10.0 mL 4.0 M acetone +10.0 mL 1.0 M HCl +10.0 mL 0.0050 M I 2 + 20.0 mL H 2 O 1
ID: 999680 • Letter: 1
Question
10.0 mL 4.0 M acetone +10.0 mL 1.0 M HCl +10.0 mL 0.0050 M I2 + 20.0 mL H2O
1. Use the dilution formula C1V1=C2V2 to calculate the initial concentrations of acetone, H+ (from HCl), and iodine I2, in the reaction mixture. Show your work and place your answers below.
[acetone]_______M [H+]_________M [I2]________M
2. Using the reaction mixture in problem 1, a student found that it took 320 seconds for the color of the I2 to disappear. Remember that initial means the initial concentration of a component in the mixture at the start of the reaction.
a) What was the rate of the reaction? rate=[I2] initial/ t
rate=________
b. Write the rate law for the reaction as it would apply to the mixture. (Fill in numbers and units for the rate and concentrations of each reactant).
rate=________
c. What are the unknowns that remain in the equation in part b.
__________ __________ ___________
Explanation / Answer
First calculate the total volume = V = 10 mL + 10 mL + 10 mL + 20 mL = 50 mL
Number of moles of acetone = 4.0 * 0.01=0.04 mol
[acetone]= 0.04 / 0.0500L
= 0.8 M
Number of moles of H+ = 1.0 * 0.01=0.01mol
[H+] = 0.01/0.050 L
=0.20 M
Number of moles of I2= 0.0050 * 0.01=5*10^-5 mol
[I2]= 5*10^-5/ 0.050 L
= 1*10^-3 M
2. Using the reaction mixture in problem 1, a student found that it took 320 seconds for the color of the I2 to disappear. Remember that initial means the initial concentration of a component in the mixture at the start of the reaction.
a) What was the rate of the reaction? rate=[I2] initial/ t
To first order, the reaction rate is 1*10^-3 M / 320 s
= 3.125*10^-6 M/s
Rate=3.125*10^-6 M/s
b. Write the rate law for the reaction as it would apply to the mixture. (Fill in numbers and units for the rate and concentrations of each reactant).
Rate = k [CO(CH3)2]^a [I2]^b [HCl]^c
3.125*10^-6 M/s = k (4 M * 10 mL / 50 mL)^a (1*10^-3 M)^b (1 M * 10 mL / 50 mL)^c
Here H+ is a catalyst and that this reaction is 1st order in acetone and 1st order in iodine .
Rate = k [CO(CH3)2] [I2]
3.125*10^-6 M/s = k (0.8M) (1.0*10^-3 M)
k = 3.90625*10^-3
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