The balanced net ionic equation for the formation of aluminum sulfate in aqueous…

CHEMISTRY · Single correct · A Level · Chemistry · Amount of substance · Amount of substance

Problem

The balanced net ionic equation for the formation of aluminum sulfate in aqueous solution is

2\,\text{Al}^{3+} + 3\,\text{SO}_4^{2-} \rightarrow \text{Al}_2(\text{SO}_4)_3

. Which of the following best explains why the coefficient in front of

\text{Al}^{3+}

must be 2 rather than 1? (a) Because the subscript “2” in

\text{Al}_2(\text{SO}_4)_3

is simply carried over as a coefficient, giving 2 in front of

\text{Al}^{3+}

during balancing. (b) Each

\text{Al}^{3+}

contributes a

+3

charge, so two of them supply the

+6

charge required to balance the

-6

charge from three sulfate ions. (c) Because

\text{Al}^{3+}

ions are known to dimerize in solution to form

\text{Al}_2^{6+}

species, the equation must therefore show two aluminum ions reacting together. (d) Because there are two aluminum atoms in

\text{Al}_2(\text{SO}_4)_3

, the reactant side must contain two

\text{Al}^{3+}

ions to conserve aluminum atoms; the charges will balance automatically.