Prepare $100mL$ of $1M$ Tris$-HCl,pH7\mathrm{.}4,$ by adding $0\mathrm{.}1$ moles $(12\mathrm{.}1g)$ of Tris base to $80mL$ of $dd{H}_{2}O,$ and then adding $12\mathrm{.}5mL$ of conc. $HCl(6M).$ Measure the $pH$ of a $1$:$20$ dilution of $1M$ stock $(0\mathrm{.}2$ mL diluted to $4mL$