3 How many molecules below have resonance structures? O₂, O₃, N₂, NO₃⁻, SO₄²⁻ (A)1 (B)2 (C)3 (D)4 (E)5

2 Which of the following acids and its sodium salt are the best combination for buffering a solution at pH 4.30? (A)chloroacetic acid (Kₐ=1.35×10⁻³) (B)propanoic acid (Kₐ=1.3×10⁻⁵) (C)benzoic acid (Kₐ=6.4×10⁻⁵) (D)hypochlorous acid (Kₐ=3.5×10⁻⁸) (E)none of the above is acceptable