The hypochlorite ion, \(\mathrm{ClO}^{-}\), acts as a weak base. (a) Is ClO a stronger or weaker base than hydroxylamine? (b) When \(\mathrm{ClO}^{-}\) acts as a base, which atom, \(\mathrm{Cl}\) or \(\mathrm{O}\), acts as the proton acceptor? (c) Can you use formal charges to rationalize your answer to part (b)?

To determine if the hypochlorite ion, \(\mathrm{ClO}^{-}\), is a stronger or weaker base than hydroxylamine (\(\mathrm{NH_2OH}\)), we need to analyze the acid dissociation constant (Ka) of their conjugate acids. The conjugate acid of \(\mathrm{ClO}^{-}\) is \(\mathrm{HClO}\) (hypochlorous acid) and the conjugate acid of hydroxylamine is \(\mathrm{NH_3OH^+}\) (hydroxylammonium ion). A lower Ka value indicates a weaker acid (and stronger conjugate base), while a higher Ka value indicates a stronger acid (and weaker conjugate base). So, we can compare the Ka values for the conjugate acids: - Ka of \(\mathrm{HClO}\): \(2.9 \times 10^{-8}\) - Ka of \(\mathrm{NH_3OH^+}\): \(7.5 \times 10^{-10}\) Since the Ka value of \(\mathrm{HClO}\) is greater than the Ka value of \(\mathrm{NH_3OH^+}\), it means that \(\mathrm{HClO}\) is a stronger acid than \(\mathrm{NH_3OH^+}\), and its conjugate base \(\mathrm{ClO}^{-}\) is a weaker base than hydroxylamine.

A base is a proton acceptor. This is, when a base reacts with an acid, it accepts a proton (H+) to form its conjugate acid. In the hypochlorite ion, \(\mathrm{ClO}^{-}\), the oxygen atom has a lone pair of electrons, which can be used to form a bond with a proton. Thus, when \(\mathrm{ClO}^{-}\) acts as a base, it is the oxygen atom that acts as the proton acceptor.

To analyze the hypochlorite ion (\(\mathrm{ClO}^{-}\)) using formal charges, we will calculate the formal charges on both the \(\mathrm{Cl}\) and \(\mathrm{O}\) atoms: Formal charge of \(\mathrm{Cl}\): - Valence electrons of Cl: 7 - Number of bonding electrons: 1 - Number of non-bonding electrons: 6 Formal charge = 7 - 0.5(1) - 6 = +0.5 Formal charge of \(\mathrm{O}\): - Valence electrons of O: 6 - Number of bonding electrons: 1 - Number of non-bonding electrons: 6 Formal charge = 6 - 0.5(1) - 6 = -0.5 The negatively charged oxygen atom is more likely to act as a proton acceptor (as a base) since it has a formal charge of -0.5. This means that the oxygen atom is electron-rich and available for accepting a proton. This rationalizes the identification of the oxygen atom as the proton acceptor in part (b).