Place the species in each of the following groups in order of increasing acid strength. Explain the order you chose for each group. a. \(\mathrm{HIO}_{3}, \mathrm{HBrO}_{3}\) b. \(\mathrm{HNO}_{2}, \mathrm{HNO}_{3}\) c. HOCl, HOI d. \(\mathrm{H}_{3} \mathrm{PO}_{4}, \mathrm{H}_{3} \mathrm{PO}_{3}\)

To compare the acid strength of \(\mathrm{HIO}_{3}\) and \(\mathrm{HBrO}_{3}\), we need to compare the electronegativity and atomic size of central atoms Iodine (I) and Bromine (Br). 1. Electronegativity: Iodine has a lower electronegativity (2.66) compared to Bromine (2.96). Lower electronegativity means the central atom can hold the bonding electrons less strongly, making it easier for the hydrogen to be lost as a proton. 2. Atomic size: Iodine has a larger atomic size than Bromine. A larger atomic size means the bonding electrons are further from the nucleus, which also makes it easier for the hydrogen to be lost as a proton. Based on these factors, we can conclude that \(\mathrm{HIO}_{3}\) has higher acid strength than \(\mathrm{HBrO}_{3}\). The order of increasing acid strength is \(\mathrm{HBrO}_{3} < \mathrm{HIO}_{3}\).

In this case, we are comparing the acid strength of two species with the same central atom: Nitrogen. However, they differ in the oxidation state of the nitrogen atom. For \(\mathrm{HNO}_{2}\) (nitrous acid), nitrogen has an oxidation state of +3, while for \(\mathrm{HNO}_{3}\) (nitric acid), nitrogen has an oxidation state of +5. A higher oxidation state means the central atom is more electron-deficient, making the O-H bond more polar and easier to break, thereby increasing the acid strength. Hence, \(\mathrm{HNO}_{3}\) is a stronger acid compared to \(\mathrm{HNO}_{2}\). The order of increasing acid strength is \(\mathrm{HNO}_{2} < \mathrm{HNO}_{3}\).

Here, we need to compare the acid strength of hypochlorous acid (HOCl) and hypoiodous acid (HOI), so we analyze factors concerning the central atoms Chlorine (Cl) and Iodine (I). 1. Electronegativity: Chlorine has a higher electronegativity (3.16) compared to Iodine (2.66). Higher electronegativity means that the O-H bond in HOCl will be more polar compared to HOI, making it easier for the hydrogen to be lost as a proton. 2. Atomic size: Chlorine has a smaller atomic size than Iodine. However, in this case, the higher electronegativity plays a more significant role in determining the acid strength. Based on these factors, we can conclude that HOCl has higher acid strength than HOI. The order of increasing acid strength is HOI < HOCl.

In this group, we need to compare the acid strength of two species with the same central atom: Phosphorus. However, they differ in the number of oxygen atoms bonded to the central atom. \(\mathrm{H}_{3} \mathrm{PO}_{4}\) (phosphoric acid) has one more oxygen atom bonded to phosphorus than \(\mathrm{H}_{3} \mathrm{PO}_{3}\) (phosphorous acid). This additional oxygen atom increases the electron deficiency of the phosphorus atom, increasing the polarity of the O-H bonds and making it easier for the hydrogen atoms to be lost as protons. Hence, \(\mathrm{H}_{3} \mathrm{PO}_{4}\) is a stronger acid compared to \(\mathrm{H}_{3} \mathrm{PO}_{3}\). The order of increasing acid strength is \(\mathrm{H}_{3} \mathrm{PO}_{3} < \mathrm{H}_{3} \mathrm{PO}_{4}\).