MISSED THIS? Read Section $18\mathrm{.}3($Page$).$

A $130\mathrm{.}0-mL$ buffer solution is $0\mathrm{.}110M$ in $N{H}_3$ and $0\mathrm{.}125M$ in $N{H}_{4}Br.$ The $K_b$ value for $N{H}_3$ is $1\mathrm{.}76{10}^{-5}.$

Part A

What mass of $HCl$ can this buffer neutralize before the $pH$ falls below $9\mathrm{.}00?$

Express the mass in grams to three significant figures.

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$m=0\mathrm{.}096$

g

Previous Answers

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To solve for the mass of $HCl$ required to bring the $pH$ to $9\mathrm{.}00,$ set up a Henderson$-$Hasselbalch equation $($ base$]/[$acid$]).$ Adding acid will increase the value of the denominator and decrease the value of the numerator in the log fraction.

The value of $K_b$ is given, so you will need to convert the value either to $p{K}_b$ then $p{K}_a$ or to $K_a$ then $p{K}_a.$

You may want to review Hint $1.$ Calculate the ratio of the buffer required at a $pH$ of $9\mathrm{.}00.$

Part B

If the same volume of the buffer were $0\mathrm{.}270M$ in $N{H}_3$ and $0\mathrm{.}395M$ in $N{H}_{4}Br,$ what mass of $HCl$ could be handled before the $pH$ falls below $9\mathrm{.}00?$

Express the mass in grams to three significant figures.

View Available Hint$($s$)$