Select the conjugate acid-base pair(s). a) HI, I b) HCHO2, SO4^2- c) CO3^2-, HCI d) PO4^3-, HPO4^2-
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Conjugate acid-base pairs are identified by the transfer of a proton (H+). A conjugate acid is the species formed when a base gains a proton, while a conjugate base is what is left after an acid has given up a proton.
a) HI, I- HI (hydroiodic acid) is an acid, and I- (iodide ion) is its conjugate base. They differ by a proton. Thus, they form a conjugate acid-base pair.
b) HCHO2, SO4^2- HCHO2 (formic acid) and SO4^2- (sulfate ion) are not a conjugate acid-base pair. The sulfate ion is the conjugate base of HSO4^- (bisulfate ion), not of formic acid.
c) CO3^2-, HCl CO3^2- (carbonate ion) can act as a base and HCl (hydrochloric acid) as an acid, but they do not form a conjugate acid-base pair. When CO3^2- accepts a proton, it becomes HCO3^- (bicarbonate ion), and when HCl donates a proton, it becomes Cl^- (chloride ion).
d) PO4^3-, HPO4^2- PO4^3- (phosphate ion) is a base, and HPO4^2- (hydrogen phosphate ion) is its conjugate acid. After PO4^3- accepts a proton, it becomes HPO4^2-. They are a conjugate acid-base pair.
So, the correct conjugate acid-base pairs among the options given are HI and I- (a), and PO4^3- and HPO4^2- (d).