CHEM 126 BASIC
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Suppose you have 0.6 M solution of acid HB. Suppose further that Ka >> 1 for this acid. Which of the following statements is true?
Ka = [H+][B-]/[HB]
Strong acids have large Ka and will fully dissociate into ions so the answer should be d as the HB should have fully dissociated
Suppose you have 0.6 M solution of acid HB. Suppose further that Ka << 1 for this acid. Which of the following statements is true?
Weak acids have small Ka and will not fully dissociate so there should be very very little of the ions readily available in the solution
Find the pH of 0.15 M CH3COOH. Ka = 1.74 x 10-5M.
acetic acid is a weak acid
Ka = [H+][CH3COO-]/[CH3COOH]
Find the pH of 0.161 M phenol, C6H5OH. The H bonded to the O is acidic, that is,
C6H5OH(aq) + H2O(l) ↔ H3O+(aq) + C6H5O–(aq). Ka = 1.0 x 10-10 M.
Use the same procedure as used in the last problem.
Calculate the approximate [OH–] and [NH4+] in a 0.15 M ammonia solution, NH3(aq).
NH3(aq) + H2O(l) ↔ OH–(aq) + NH4+(aq). Kb = 1.75 x 10-5M.
Use the same procedure as used in the last 2 problems. Details for those who want a little extra help:
Calculate the pH of 0.029 M ammonia.
NH3(aq) + H2O(l) ↔ OH–(aq) + NH4+(aq) Kb = 1.75 x 10-5
1.75e-5 = x^2/0.029
Which of the following compounds are Bronsted-Lowry bases?
Select one or more:
Determine the conjugate base for the acid HF in ammonia.
HF + NH3 → NH4+ + F–
Indicate whether the ion is acidic, basic, or neutral by writing A, B, or N, respectively.
F– (HF is not one of the 6 strong acids)
Cl– (Is HCl one of the 6 strong acids?)
CH3COO– (the acetate ion)
HCOOH (formic acid)
HCOO– (formate ion)
Indicate whether the species is acidic, basic, or neutral by writing A, B, or N, respectively.
CH3NH2 (like NH3 but one of the H is replaced with CH3)
Match strongest to weakest acid.
Remember the larger Ka, the stronger the acid.
Match strongest to weakest conjugate base.
Remember the weaker the acid, the stronger the conjugate base.
Remember, to prepare a buffer solution you must use a weak acid and its conjugate base or a weak base and its conjugate acid!
What is the pKa for phenol? Ka = 1.0 x 10-10.
pKa = -log(Ka)= -log(10e-10)
What is the pH of a buffer solution of phenol and its conjugate base. [C6H5OH] = 0.41 M and [C6H5O]– = 0.78 M.
pH= pKa +log ( CB/A)
=10 + log(.78/.41)