HW 2 #3

[mya warner 2C]

For #3 on the HW this week, the Ka value was less than 10^-3, which I know is an indicator that we don't have to use the quadratic equation, however that was not the case of this problem and the only way I could get the right answer was through the quadratic formula. Can someone explain the logic behind this?

[905783577]

10^-3 isn't a foolproof guideline. Since the Ka was on the boundary of 10^-3, the value for x wasn't negligible in this case.

[Gianna Sciole 2F]

another way to check is the percent ionization. if the percent ionization is less than 5%, it is okay to not use the quadratic equation and eliminate the x in the denominator, however, if it is above 5%, you have to use the quadratic formula. hope this helped!

[905767718]

Since both the initial molar concentration and the Ka value were both very small, I assumed that it wouldn't be safe to approximate in this case. You can always check the % protonation at the end to see whether or not the approximation was valid.

[Ethan_Choi_2I]

I think if the initial molar concentration is 1000 times larger than the Ka value, it would be safe to approximate and the quadratic equation is likely not needed. If the Initial molar concentration value is even slightly less than 1000 times larger than the initial Ka value, you cannot assume that it would be safe to approximate.

[Kayla Ziebell 1H]

Using the quadratic equation is always more accurate. By simplifying the math and assuming x is very small and disregarding it, we are only getting an approximation.