A sample of is placed in a beaker

CHEMISTRY · Multi-part · A Level · Chemistry · Acids and bases · Acids and bases

Problem

100.0\,\text{mL}

sample of

0.150\,\text{M}\,Na_2CO_3(aq)

is placed in a beaker. Hydrochloric acid,

0.100\,\text{M}

, is added dropwise to the solution at

25\,^{\circ}\text{C}

. Assume volumes are additive and neglect any change in temperature. (1) Part 1: (a) After exactly

60.0\,\text{mL}

of the HCl solution has been added, list all ionic species that remain in appreciable amounts. For each species, calculate its concentration in the new total volume. (2) Part 2: (b) At this point in the titration, determine whether the solution qualifies as a buffer. Justify your answer with reference to the species identified in part (a). (3) Part 3: (c) Calculate the pH of the solution after the

60.0\,\text{mL}

addition. The relevant acid-dissociation constants are

K_{a_1}(H_2CO_3) = 4.3 \times 10^{-7}

and

K_{a_2}(H_2CO_3) = 5.6 \times 10^{-11}

Related theory

Equilibrium
Buffer Solutions
Acid-Base Titrations

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