A buffer is made using only Tris $($weak base$)$ and HCl$.$ What volume $($in mL$)$ of $1\mathrm{.}00$ M HCl would be used to make $0\mathrm{.}40$ L of a buffer solution with a total buffer concentration $([$Tris$]+[$TrisH$+])$ of $0\mathrm{.}15$ M$,$ and pH $7\mathrm{.}9?$

TrisH$++$ H$2$O $$ Tris $+$ H$3$O$+$

Data:

pKa$($TrisH$+)=8\mathrm{.}30$

$($Enter your answer to $1$ decimal place$)$

Answer:

$15\mathrm{.}6$ Incorrect Response $(42\mathrm{.}9)$