Label each of the following as being a strong acid, a weak acid, or a species with negligible acidity. In each case write the formula of its conjugate base, and indicate whether the conjugate base is a strong base, a weak base, or a species with negligible basicity: \((\mathbf{a}) \mathrm{HCOOH}\), \((\mathbf{b})\mathrm{H}_{2},(\mathrm{c}) \mathrm{CH}_{4},(\mathbf{d}) \mathrm{HF},(\mathbf{e}) \mathrm{NH}_{4}^{+}\)

We have five species to analyze: \(\mathrm{HCOOH}\), \(\mathrm{H}_{2}\), \(\mathrm{CH}_{4}\), \(\mathrm{HF}\), and \(\mathrm{NH}_{4}^{+}\). 1. \(\mathrm{HCOOH}\) is formic acid, a weak acid. 2. \(\mathrm{H}_{2}\) is molecular hydrogen, a species with negligible acidity. 3. \(\mathrm{CH}_{4}\) is methane, a species with negligible acidity. 4. \(\mathrm{HF}\) is hydrofluoric acid, a weak acid. 5. \(\mathrm{NH}_{4}^{+}\) is the ammonium ion, a weak acid.

We'll now write the formula of the conjugate base of each species: 1. \(\mathrm{HCOOH} \rightarrow \mathrm{HCOO}^{-}\) 2. \(\mathrm{H}_{2} \rightarrow \mathrm{H}^{-}\) 3. \(\mathrm{CH}_{4} \rightarrow \mathrm{CH}_{3}^{-}\) 4. \(\mathrm{HF} \rightarrow \mathrm{F}^{-}\) 5. \(\mathrm{NH}_{4}^{+} \rightarrow \mathrm{NH}_{3}\)

Now we will determine whether each conjugate base is a strong base, weak base, or has negligible basicity: 1. \(\mathrm{HCOO}^{-}\) is the formate ion, a weak base. 2. \(\mathrm{H}^{-}\) is the hydride ion, a strong base. 3. \(\mathrm{CH}_{3}^{-}\) is the methyl anion, a species with negligible basicity. 4. \(\mathrm{F}^{-}\) is the fluoride ion, a weak base. 5. \(\mathrm{NH}_{3}\) is ammonia, a weak base. In summary, we have: a) \(\mathrm{HCOOH}\) is a weak acid, its conjugate base \(\mathrm{HCOO}^{-}\) is a weak base. b) \(\mathrm{H}_{2}\) has negligible acidity, its conjugate base \(\mathrm{H}^{-}\) is a strong base. c) \(\mathrm{CH}_{4}\) has negligible acidity, its conjugate base \(\mathrm{CH}_{3}^{-}\) has negligible basicity. d) \(\mathrm{HF}\) is a weak acid, its conjugate base \(\mathrm{F}^{-}\) is a weak base. e) \(\mathrm{NH}_{4}^{+}\) is a weak acid, its conjugate base \(\mathrm{NH}_{3}\) is a weak base.