Question

20 mL of 4.0 M acetone + 10 mL of 1.0 M HCl + 20 mL of 0.0050 M I₂

If the reaction is zero order in I₂, approximately how long would it take for the I₂ color to disappear at the temperature of the reaction mixture 20 mL of 4.0M acetone + 10 mL of 1.0 M HCl + 10 mL 0f 0.0050M I2 + 10 mL H2O .

Answer 1

The theory you need to know to solve this problem:

CH₃COCH₃ + I₂ = CH₃COCH₂I + H⁺ + I^-

rate = k[acetone]^m[I₂]ⁿ[H⁺]^p

If the rate of this reaction is expressed as the change in the concentration of I₂ with respect to change of time, we get

rate = d[I₂]/dt

As the reaction is zero order with respect to iodine, the rate of the reaction does not depend on [I₂]. If both acetone and H+ are present in the mixture at much higher concentrations than I2, their concentrations will not practically change during the reaction, and the rate will remain constant until all the iodine is reacted. If it takes t seconds for the color of the solution having an initial concentration of iodine = [I₂]⁰ to disappear, the rate of the reaction would be

rate = d[I₂]/dt = [I₂]⁰ /t

Now come to the question,

You need to have the initial concentration of iodine and the rate of the equation (which you have not provided with the question, so let it be r M.sec^-1 ) to calculate the time(t).

[I₂]⁰ in the mixture (20 mL of 4.0M acetone + 10 mL of 1.0 M HCl + 10 mL 0f 0.0050 M I₂ + 10 mL H₂O)

= [10*0.005/(20+10+10+10)] M

= 0.001 M

Time required to disappear the color of the solution

= 0.001 M/ r M.sec^-1

=( 0.001/r) sec