For which of the reactions is the net ionic equation: H^+ + OH^- -> H₂O?

Here are the solutions to questions 23 through 29:

23. For which of the reactions is the net ionic equation: $H^+ + OH^- \rightarrow H_2O$? This net ionic equation represents the neutralization of a strong acid by a strong soluble base.

    • (1) $CH_3COOH + NaOH \rightarrow$ (Weak acid + Strong base) - Net ionic equation: $CH_3COOH(aq) + OH^-(aq) \rightarrow CH_3COO^-(aq) + H_2O(l)$.
    • (2) $HNO_3 + Mg(OH)_2 \rightarrow$ (Strong acid + Insoluble/sparingly soluble strong base) - Net ionic equation: $2H^+(aq) + Mg(OH)_2(s) \rightarrow Mg^{2+}(aq) + 2H_2O(l)$.
    • (3) $H_3PO_4 + Ba(OH)_2 \rightarrow$ (Weak acid + Strong base) - Net ionic equation involves $H_3PO_4$ and $OH^-$.
    • (4) $HCl + KOH \rightarrow$ (Strong acid + Strong soluble base) - Net ionic equation: $H^+(aq) + OH^-(aq) \rightarrow H_2O(l)$.
    • (5) $H_2CO_3 + LiOH \rightarrow$ (Weak acid + Strong base) - Net ionic equation involves $H_2CO_3$ and $OH^-$.

    Only reaction (4) involves a strong acid and a strong soluble base that fully dissociates, resulting in the net ionic equation $H^+ + OH^- \rightarrow H_2O$.

    The correct answer is C. 4.

24. Which one of the following represents the net ionic equation for the reaction of nitric acid with aluminum hydroxide?

    • Step 1: Write the balanced molecular equation. Nitric acid ($HNO_3$) is a strong acid. Aluminum hydroxide ($Al(OH)_3$) is an insoluble base. $$3HNO_3(aq) + Al(OH)_3(s) \rightarrow Al(NO_3)_3(aq) + 3H_2O(l)$$
    • Step 2: Write the complete ionic equation. Strong acids and soluble ionic compounds are written as dissociated ions. Insoluble compounds remain as solids. $$3H^+(aq) + 3NO_3^-(aq) + Al(OH)_3(s) \rightarrow Al^{3+}(aq) + 3NO_3^-(aq) + 3H_2O(l)$$
    • Step 3: Identify and cancel spectator ions. The spectator ion is $NO_3^-$. $$3H^+(aq) + Al(OH)_3(s) \rightarrow Al^{3+}(aq) + 3H_2O(l)$$

    The correct answer is A. $3H^+ + Al(OH)_3 \rightarrow Al^{3+} + 3H_2O$.

25. Which one of the following is an amphoteric metal hydroxide? An amphoteric substance can react as both an acid and a base.

    • A. $KOH$ (Potassium hydroxide) is a strong base.
    • B. $Ba(OH)_2$ (Barium hydroxide) is a strong base.
    • C. $Pb(OH)_2$ (Lead(II) hydroxide) is known to be amphoteric, reacting with strong acids and strong bases.
    • D. $LiOH$ (Lithium hydroxide) is a strong base.

    The correct answer is C. $Pb(OH)_2$.

26. According to the Lewis theory, a base ______.

    • A. is a proton acceptor. (Bronsted-Lowry base)
    • B. is a proton donor. (Bronsted-Lowry acid)
    • C. makes available a share in a pair of electrons. (This is the definition of a Lewis base, an electron-pair donor.)
    • D