April 03, 2020, 07:58:35 PM
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Topic: Acid and basic solutions. PH and pOH calculations.  (Read 191 times)

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Offline PotatoMax103

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Acid and basic solutions. PH and pOH calculations.
« on: March 24, 2020, 11:42:48 PM »
250 ml of a 1.5X10-2 M acetic acid solution are mixed with 450 ml of a solution of the same acid of concentration 1.2X10-3 M. If the ionization constant is 1.8X10-5. Calculate: a.- α b.-% α c.- [H +] d.- pH e.- pOH f.- [OH-] Let's see, as far as I understand a solution for solute and solvent, right? In this problem, since they don't mention which is the solvent, I suppose that it is water, so the equation remains:
CH3COOH + H2O = H3O + + CH3COO-
Although it could also be
CH3COOH = CH3COO- + H +
Well in case it is the first equation, there is one of my drawbacks as I can calculate the concentration of hydrogen and hydroxy, in addition to the pH and pOH, if none of them is present in the products.
For its part, in case it is the second equation, how to calculate the concentration of hydrogen and with it the pH, what happens is that in all the examples that I have seen in all those that work with acids, the pOH and the concentration of oxydrile in them, I don't know if it's because they have any special properties (?)
The second question I have is how would I go about posing the picture? What I assumed is that I would add the concentrations of both solutions and that would give me the initial concentration and then subtract x from that concentration at equilibrium time, but I'm not sure :(

Offline AWK

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Re: Acid and basic solutions. PH and pOH calculations.
« Reply #1 on: March 25, 2020, 02:19:28 AM »
Instead of empty thinking, proceed to specific calculations:
a - simple mixing of the solution
b - you need to assume the density of the solution, but for these concentrations it is obvious
c - the question clearly indicates which dissociation equation you have to choose - note very low concentration values
d - you have a concentration of H+ - use the definition of pH
e, f - pOH and [OH-] are simply dependent on [H+] or pH

In addition, it is worth reading the relevant chapter in your textbook.
AWK

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