C$.$ Determination of the Dissociation Constant of a Weak Acid

$pH$ of half$-$neutralized acid solution

$4\mathrm{.}18$

$H^{+}$in half$-$neutralized solution

${10}^{-4}*4\mathrm{.}18=6\mathrm{.}606*{10}^{-5}$

$K_a$ for unknown acid $6\mathrm{.}61*{10}^{-5}$

Unknown number

D$.$ Demonstration of Buffering Action

$pH$ after addition of NaOH

change in $pH$ from Part $C$

$10\mathrm{.}11$

$pH$ of saturated $Mg(OH{)}_2$ solution

$11\mathrm{.}66$

$pH$ of saturated $Ca(OH{)}_2$ solution

E$.$ Determination of the Solubility Product of Slightly Soluble Hydroxides

THOUGHT

a$)$ Calculate the percent ionization for each of the three $H{C}_2{H}_3{O}_2$ solutions. Show your work.

$($Hint: Compare the $H^{+}$present in each solution with the amount that would be present if the acid

completely dissociated.$)$

$0\mathrm{.}01=>4\mathrm{.}22\%$

$0\mathrm{.}001=>13\mathrm{.}4\%$

$0\mathrm{.}1=>1\mathrm{.}3440$

$0\mathrm{.}1=>1\mathrm{.}3440,1\mathrm{.}8*{10}^{-5}=\frac{A^2}{0\mathrm{.}01}$

$8*{10}^{-5},\frac{1\mathrm{.}34*{10}^{-3}}{0\mathrm{.}1}100,0\mathrm{.}42*{10}^{-3}$

$[H^{+}]=1\mathrm{.}8*{10}^{-5}=\frac{A^2}{0\mathrm{.}1},1\mathrm{.}34\%,\frac{0\mathrm{.}42*{10}^{-3}}{0\mathrm{.}01}100=4\mathrm{.}22$

$A^2=(1\mathrm{.}8*{10}^{-5})(0\mathrm{.}1),$

$A=1\mathrm{.}34*{10}^{-3}$

$A=(1\mathrm{.}8*{10}^{-5}*0\mathrm{.}001)$

$\frac{0\mathrm{.}42*{10}^{-3}}{0\mathrm{.}01}100=4\mathrm{.}22$

$=1\mathrm{.}34*{10}^{-4}$

$\frac{1\mathrm{.}34*{10}^{-4}}{0\mathrm{.}001}100=13\mathrm{.}45$

b$)$ How does the percent ionization of the acid change as its concentration is varied?

Percent ionization of a wenk acid increases