Experiment $25$

Advance Study Assignment: pH Measurements$-$Buffers and Their Properties

A solution of a weak acid was tested with the indicators used in this experiment. The colors observed were as follows:

$\backslash$table$[[$Methyl violet,violet,Congo red,orange$-$red$],[$Thymol blue,yellow,Bromocresol green,blue$-$green$],[$Methyl yellow,yellow,,$]]$

What is the approximate $pH$ of the solution?

$2.$ The ammonia $(N{H}_3)$ molecule is the conjugate base of the $N{H}_4^{+}($called "ammonium"$)$ ion, a weak acid. An aqueous solution of $N{H}_3$ has a pH of $11\mathrm{.}6.$ Write the net ionic equation for the reaction that makes an aqueous solution of $N{H}_3$ basic. $($The answer looks very similar to Eq$.5$ in the introduction to this experiment.$)$

$3.$ The $pH$ of a $0\mathrm{.}010M$ HOBr solution is $5\mathrm{.}3.$

a$.$ What is $H^{+}$in that solution?

M

b$.$ What is $OB{r}^{-}?$ What is HOBr $?($Where do the $H^{+}$and $OB{r}^{-}$ions come from?$)$

$M$;

M

c$.$ What is the value of $K_a$ for HOBr $?$ What is the value of $p{K}_a?$

$($continued on following page$)$