Answer
a. HI is the acid and I- is its conjugate base.
b. This pair is not a conjugate acid-base pair.
c. Phosphate ion is the conjugate acid.
d. This pair is not a conjugate acid-base pair.
Work Step by Step
a. HI donates proton and converts to Iodide ion. So, HI is the acid and I- is its conjugate base.
b. This pair is not a conjugate acid-base pair because no protons are accepted or donated.
c. Phosphate ion is the conjugate acid because it can donate a proton.
d. This pair is not a conjugate acid-base pair because no protons are accepted or donated.