G-Chem Question Help

[luv8724]

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Hmm I may be just dumb or just filled with so much of info that my mind has gone somewhere but help me on this plz..

In order to find pH of a solution.. do we always change it to Kb (of Ka given) and then later subtract pOH from 14?

Ex) If we titrated 100ml of HClO with 0.1M NaOH (40mL)... I found that the conc. of HClO was 0.04M in order to reach eq. point... and Ka given at 3.00x10^-8

But when since we know the conc. HClO.. can't we just do x^2 = (3.00x10^-8)(0.040M)
and then just negative log it? lol

 

[BRZ24]

Hmm I may be just dumb or just filled with so much of info that my mind has gone somewhere but help me on this plz..

In order to find pH of a solution.. do we always change it to Kb (of Ka given) and then later subtract pOH from 14?

Ex) If we titrated 100ml of HClO with 0.1M NaOH (40mL)... I found that the conc. of HClO was 0.04M in order to reach eq. point... and Ka given at 3.00x10^-8

But when since we know the conc. HClO.. can't we just do x^2 = (3.00x10^-8)(0.040M)
and then just negative log it? lol

To find a pH of a solution You need the [H+] always.

now the problem can directly give you the ka and concentration of the weak acid or the concentration of the weak base & its kb.

If they give you the concentration of the weak base and its kb, you can find the concentration of OH and POH. Then just subtract from 14 to find the pH.

And yes, you can just take square root of the concentration of the weak acid* ka) if given both.

 

[luv8724]

Let's say if I was to find the pH of the solution at the eq. point? then what do I do?..
the solution is using ClO- and use KaKb = 1x10^-14 to find Kb and then find the pH.
At eq.. [HClO] = [ClO-] right?...
why wouldn't just use the conc. of HClO and Ka? or is it just the preference lol

 

[BRZ24]

Let's say if I was to find the pH of the solution at the eq. point? then what do I do?..
the solution is using ClO- and use KaKb = 1x10^-14 to find Kb and then find the pH.
At eq.. [HClO] = [ClO-] right?...
why wouldn't just use the conc. of HClO and Ka? or is it just the preference lol

In your case, the equivalence point is the point where you have added an equivalent amount of base to completely neutralize the weak acid. Your pH at that point will be greater than 7 since you are using a strong base and a weak acid.

also, the concentration of weak acid is equal to the concentration of its confugate base at HALF equivalence point(NOT equivalence point).



It would be helpful if you can type the original question out.