PH of solution (not enough infromation?)

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The discussion focuses on calculating the pH and concentrations of species in solutions of ethylammonium chloride and aluminum nitrate. For the ethylammonium chloride solution, the Kb value for ethylamine is used to find the concentrations of C2H5NH3+, Cl-, and H+. The participant deduces that the concentration of C2H5NH3+ is 0.25M, with a negligible dissociation leading to a calculated [H+] of 2.1e-6M. For the aluminum nitrate solution, the Ka value for Al(H2O)6 3+ is provided to establish an equilibrium constant equation. The thread emphasizes the importance of understanding equilibrium setups for both problems.
Haxx0rm4ster
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Both are confusing me. I don't know what information to use (K values)
I'd really appreciate some help!


Calculate the concentration of all species present in a 0.25M solution of ethylammonium chloride (C2H5NH3CL)
(Not sure you if you may need this, but C2H5NH2 has a Kb value of 5.6*10^-4... it is not given in the question, it's in the appendixes of my book, which are used a lot in these problems)



Calculate the pH of a 0.050M Al(NO3)3 solution. Ka value for Al(H2O)6 3+ is 1.4*10^-5.



EDIT: hmmm after reading analyzing it a little bit, I think I'm supposed to find the Kb of C2H5NH2 for the first one.. in other words
1ee-14/5.6ee-4
right?
And that would lead to the answer being
[C2H5NH3 +] = 0.25M (% dissociation is insignificant)
[Cl -] = 0.25M
[H +] = [C2H5NH2] = 2.1ee-6M
Does this look right?
 
Last edited:
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Hi, both of these questions involve setting up an equilibrium constant equation. So you can start by showing us this setup for both problems.
 

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