A student records buffer data and constructs a graph of measured pH (vertical axis)…

CHEMISTRY · Single correct · A Level · Chemistry · Acids and bases · Acids and bases

Problem

A student records buffer data and constructs a graph of measured pH (vertical axis) versus

\log\left(\dfrac{[A^-]}{[HA]}\right)

(horizontal axis). The graph is a straight line with slope close to 1. Which quantity is represented by the

y

-intercept of this plot? (a) the value of

K_a

for the acid (b) the initial

\mathrm{pH}

of the weak acid solution before any conjugate base is added (c) the value of

pK_a

for the acid (d) the equivalence-point

\mathrm{pH}

during titration of the acid with a strong base