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Homework 6D.7a

Posted: Tue Jan 21, 2020 11:51 pm
by Lindsey Chheng 1E
Find the initial concentration of the weak acid or base in the following aqueous solutions. a) solution of HClO with pH = 4.60. I know how to find the concentration of H3O+ using the given pH but I don't know what to do after this. Am I supposed to look up the Ka and set up a Ka expression with the initial concentration of the weak acid as the variable?

Re: Homework 6D.7a

Posted: Wed Jan 22, 2020 12:06 am
by JChen_2I
I believe you have to search up the Ka value. I found it to be 3.0*10^-8. Use the hydronium concentration you found and plug it into the ice table. Then take the values from the ice table and set up an equation equal to Ka to solve for the initial concentration

Re: Homework 6D.7a

Posted: Wed Jan 22, 2020 12:06 am
by Julie Park 1G
Yes, I believe that you should look up the Ka. I think that questions such as these are supposed to provide the Ka in the problem unless previously stated in a table of Ka, but I can't seem to find the Ka for HClO in the textbook.
After finding Ka, set up the Ka expression using information deduced by an ICE table. HClO should be represented as x and its final component should be described as .
Solving for x will give you the initial concentration in question

Re: Homework 6D.7a

Posted: Wed Jan 22, 2020 12:11 am
by Eileen Si 1G
Yes, you are on the right track. For HClO, the Ka = 3.0 x 10^-8, and the variable in the Ka expression would be the amount of molar concentration of HClO, which you can find since you are given the pH. So, it would be Ka = 3.0 x 10^-8 = [HClO]^2/x-[HClO], and you would just solve for x.