Two weak, monoprotic species are mixed in aqueous solution. A partial equation for…

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

Problem

Two weak, monoprotic species are mixed in aqueous solution. A partial equation for the resulting proton-transfer reaction is written below, but the products are not shown. HCO3−(aq)+H2PO4−(aq)⇌  ?  +  ?HCO_3^-(aq)+H_2PO_4^-(aq)\rightleftharpoons\;?\;+\;? The following table lists the first ionization constants at 25 °C.
SpeciesKaK_a
H2CO3H_2CO_34.3×10−74.3\times10^{-7}
HCO3−HCO_3^-4.7×10−114.7\times10^{-11}
H3PO4H_3PO_47.1×10−37.1\times10^{-3}
H2PO4−H_2PO_4^-6.3×10−86.3\times10^{-8}
Answer the questions that follow. (a) Complete the chemical equation by writing the two missing product species. (b) List the two conjugate acid–base pairs that participate in the completed equation. (c) Using the KaK_a values provided, determine the predominant direction (left or right) in which the equilibrium lies. Justify your answer by comparing appropriate numerical values.

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