textbook 7A #17

[Kaylee Nezwek 1D]

hey! question #17 in 7A gives a series of experiments and asks to determine the rate law, the reaction order, and the rate constant. I determined the rate law to be rate = k [A] [B]^2 [C]^2, which was correct according to the solutions manual, but when I plugged in concentrations to get the rate constant, I got the wrong answer. For experiment #1, the concentrations were all 1.25, so I plugged this value into rate = k [1.25] [1.25]^2 [1.25]^2. does anyone know why this would give me the wrong answer/what values I should have used?

[Giselle Granda 3F]

I also used the first experiment and was having the same issue, so since the units were in mmol per liter, I converted each to mol/L and it worked out for me. I am not sure why that is but it gave a different and correct answer. Hopefully that works for you!

[Kaitlin Eblen 1I]

hey! question #17 in 7A gives a series of experiments and asks to determine the rate law, the reaction order, and the rate constant. I determined the rate law to be rate = k [A] [B]^2 [C]^2, which was correct according to the solutions manual, but when I plugged in concentrations to get the rate constant, I got the wrong answer. For experiment #1, the concentrations were all 1.25, so I plugged this value into rate = k [1.25] [1.25]^2 [1.25]^2. does anyone know why this would give me the wrong answer/what values I should have used?

Your units for the the concentrations and A, B, and C as well as the rate are in mmol. So, you got the correct value but your units for k (likely L^4/ mmol^4*s) are different than the answer key's. I attached a picture but you need to convert k to L^4/mol*s.

I converted at the end but you can also convert all the concentration values and the initial rate to mol (rather than mmol) before solving for "k".