PH:
calculating pH
starting from a solution of pure water at 25°, we can derive an equilibrium between the concentrations of hydroxide and hydrogen
ions:
we can derive three different situations based on the relationships between the ion concentrations:
the pH is a logarithmic scale base 10 that defines the concentration of H+ ions and the acidy of the solution.
another fundamental relationship for calculating pH and pOH is
weak acids and bases are weak electrolytes, so they do not completely dissociate in solution unlike strong acids and bases.
for weak acids, the pH depends on the dissociations constant Ka:
the same applies to weak bases:
an acid-base reaction is defined as such when an acid and a base in solution form a salt and water according to the reaction:
the pH of the solution will shift towards neutrality:
saline hydrolysis:
when a. salt is dissolved in aqueous solution, potentially causing a pH change in the final solution.
the hydrolysis of salt can be neutral, acidic or basic depending on ion dissociation. for the metal, strong bases are those formed by
elements from group 1 and group II. for the non-metal, the starting acid must be derived by adding an H+ equal to the anion’s
oxidation number, to then determine if it is strong or weak.
strong acid+ strong base= neutral hydrolysis.
strong acid+ weak base= acidic hydrolysis.
weak acid+ strong base= basic hydrolysis.
weak acid+ weak base= depends on Ka and Kb.
buffer solutions:
they not significantly change their pH upon adding a moderate amount of strong acid or base.
they are composed of a weak acid and its conjugate base and a weak base and it’s conjugate acid.
the henderson-hasselbach equation is used to calculate the pH of a buffer solution:
the buffering capacity is a measure of the ability to resist pH changes and is directly proportional to the concentration of the buffer
solution.
Kw Ht OH 10ᵗʰHt OH 10 7
acidic solution
se èE
PH Cogo Ht
POH Cog 10 OH
PH POH 14
HVataciot
OH Up base HABOH A
Mat NON_
pH pkat cog io
