achieve week 2 assignment

[905934944]

Hi,
for question 3 of the achieve week 2 assignment. Why do they consider percent ionization negligible if the Ka is less than 5% of the amount of acid? During lecture, Professor Lavelle said that when the Ka is less than 10^-3 the percent ionization is considered negligible. Which criteria for percent ionization neglibility should we follow?
Thank you!

[Jenny Dis1D]

Hi! When I was doing this problem and using the feedback/ hints to help me, it said that it was negligible if Ka was less than 1000, so that corresponds with what Professor Lavelle said in class, so you should use that for percent ionization eligibility!

[Layla Qumsieh 3C]

Typically those two criteria will line up. If Kc is less than 10^-3, you should be good to consider x negligible. I personally like to still find the percent ionization afterwards to make sure that I didn't make a mistake, in case I actually have to do the quadratic formula. But typically when Kc is less than 10^-3, percent is less than 5%.

[Shania Hao 3L]

If the Ka value is less than 10^-3, this already tells you that the x value that you are going to get is small. Thus, you can consider the x in the denominator negligible and simplify the process. The 5% check at the end reconfirms that the value of x was negligible because it would have been too small in the denominator to have made a difference in the overall answer.

[Adam Jameel 2A]

They are actually about the same because on the feedback, it gave me the same number that the Professor gave us in the lecture!