Question 4.11: Write a balanced net ionic equation for the reaction between...
Write a balanced net ionic equation for the reaction between aqueous sulfuric acid and barium hydroxide as pictured in Figure 4.19.
Collect and Organize We are asked to write a balanced net ionic equation given the names of the reactants. Figure 4.19 shows that the reaction produces a white precipitate.
Analyze First, we need to write a balanced molecular equation for the reaction. Next we must identify which reactants and products are soluble in water. We write any soluble ionic compounds as ions, leaving any precipitates and molecular compounds unchanged. Finally, we will simplify the overall ionic equation by removing any spectator ions that appear on both sides of the equation to obtain the net ionic equation.
Note that sulfuric acid is a strong acid. However, as discussed earlier in this chapter, its first proton completely dissociates but its second proton does not:
H_{2}SO_{4}(aq) → H^{+}(aq) + HSO_{4}^{-}(aq) HSO_{4}^{-}(aq) \xrightleftharpoons{} H^{+}(aq) +SO_{4}^{2-}(aq)
Therefore the correct way to write the ionic species present in solution in an overall ionic equation when sulfuric acid is a reactant is H^{+}(aq) +HSO_{4}^{2-}(aq), not 2 H^{+}(aq) +SO_{4}^{2-}(aq).
Solve
1. Molecular equation: Ba(OH)_{2}(aq) + H_{2}SO_{4}(aq) → BaSO_{4}(s) + 2 H_{2}O(\ell)
2. Overall ionic equation:
Ba^{2+}(aq) + 2 OH^{-}(aq) + H^{+}(aq) + HSO_{4}^{-}(aq) → BaSO_{4}(s) + 2 H_{2}O(\ell)
3. The equation cannot be simplified any further, so the net ionic equation is the same as the overall ionic equation in this case.
Think About It The reaction between barium hydroxide and sulfuric acid is both a neutralization reaction and a precipitation reaction. The neutralization is indicated by the formation of a salt (BaSO_{4}) and water; because the salt is insoluble, the reaction is also a precipitation reaction.