58 865
Assignments Done
Successfully Done
In March 2018
Your physics homework can be a real challenge, and the due date can be really close — feel free to use our assistance and get the desired result.
Be sure that math assignments completed by our experts will be error-free and done according to your instructions specified in the submitted order form.
Our experts will gladly share their knowledge and help you with programming homework. Keep up with the world’s newest programming trends.

Answer on Other Chemistry Question for Dee

Question #6521
if a weak acid, HA, is 3% dissociated in a 0.25M solution, calculate the Ka and the pH of the solution.
Expert's answer
a=3% (0.03)
Ka-? pH-?

HA <=>H+ +

a=(K/C) ^ (1/2)
a^ 2= K/C
K=(a^ 2)/C
K= (0.03^ 2)

[H+]=(K*C) ^ (1/2)=0.03


Need a fast expert's response?

Submit order

and get a quick answer at the best price

for any assignment or question with DETAILED EXPLANATIONS!


27.01.2013 19:59

The % dissociated (or value "a") tells you that you have 3% of A- and 97% of HA. For a 0.25M solution, that means you have (0.97 * 0.25)M HA present, (0.03 * 0.25)M A- present, and (0.03 * 0.25)M H+ present. Putting these concentrations into the equation doesn't give you K = 0.0036.

In fact, the first problem is that whoever answered before assumes "% dissociated" is the concentration of H+ present...a mistake which can be seen in solving the second part.

Leave a comment

Ask Your question