Question

For each conjugate acid-base pair, identify the first species as an acid or a base and the second species as its conjugate acid or base. In addition, draw Lewis structures for each species, showing all valence electrons and any formal charge. (a) \(\mathrm{HCOOH} \mathrm{HCOO}^{-}\) (d) \(\mathrm{HCO}_{3}^{-} \mathrm{CO}_{3}^{2-}\) (b) \(\mathrm{NH}_{4}^{+} \mathrm{NH}_{3}\) (c) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{O}^{-} \quad \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{OH}\) (g) \(\mathrm{CH}_{3} \mathrm{~S}^{-} \quad \mathrm{CH}_{3} \mathrm{SH}\) (f) \(\mathrm{CH}_{3} \mathrm{CH}_{3} \mathrm{CH}_{3} \mathrm{CH}_{2}^{-}\)

Short answer

Question: Identify the acid or base in each pair and draw their Lewis structures. Pair (a): HCOOH and HCOO- Answer: HCOOH is the acid and HCOO- is the conjugate base. Lewis structures: HCOOH: O || H - C - O - H | H HCOO-: O- || H - C - O | H Pair (d): HCO3- and CO3^2- Answer: HCO3- is the acid and CO3^2- is the conjugate base. Lewis structures: HCO3-: O- O || \\ H - C - O | O CO3^2-: O^2- O || \\ C - O | O Pair (b): NH4+ and NH3 Answer: NH4+ is the acid and NH3 is the conjugate base. Lewis structures: NH4+: H | H - N+ - H | H NH3: H | H - N - H : Pair (c): CH3CH2O- and CH3CH2OH Answer: CH3CH2O- is the base and CH3CH2OH is the conjugate acid. Lewis structures: CH3CH2O-: H - C - C - O- | | H H CH3CH2OH: H - C - C - O - H | | H H Pair (g): CH3S- and CH3SH Answer: CH3S- is the base and CH3SH is the conjugate acid. Lewis structures: CH3S-: H - C - S- | H CH3SH: H - C - S - H | H Pair (f): CH3CH3CH3CH2- and CH3CH3CH3CH3 Answer: CH3CH3CH3CH2- is the base and CH3CH3CH3CH3 is the conjugate acid. Lewis structures: CH3CH3CH3CH2-: H - C - C - C - C- | | | H H H CH3CH3CH3CH3: H - C - C - C - C - H | | | H H H

Step-by-step solution

Pair (a): HCOOH and HCOO-

HCOOH is the acid, as it can donate a proton to form HCOO-. HCOO- is its conjugate base because it can accept a proton to form HCOOH. The Lewis structures are: HCOOH: O || H - C - O - H | H HCOO-: O- || H - C - O | H

Pair (d): HCO3- and CO3^2-

HCO3- is the acid, as it can donate a proton to form CO3^2-. CO3^2- is its conjugate base because it can accept a proton to form HCO3-. The Lewis structures are: HCO3-: O- O || \\ H - C - O | O CO3^2-: O^2- O || \\ C - O | O

Pair (b): NH4+ and NH3

NH4+ is the acid, as it can donate a proton to form NH3. NH3 is its conjugate base because it can accept a proton to form NH4+. The Lewis structures are: NH4+: H | H - N+ - H | H NH3: H | H - N - H :

Pair (c): CH3CH2O- and CH3CH2OH

CH3CH2O- is the base, as it can accept a proton to form CH3CH2OH. CH3CH2OH is its conjugate acid because it can donate a proton to form CH3CH2O-. The Lewis structures are: CH3CH2O-: H - C - C - O- | | H H CH3CH2OH: H - C - C - O - H | | H H

Pair (g): CH3S- and CH3SH

CH3S- is the base, as it can accept a proton to form CH3SH. CH3SH is its conjugate acid because it can donate a proton to form CH3S-. The Lewis structures are: CH3S-: H - C - S- | H CH3SH: H - C - S - H | H

Pair (f): CH3CH3CH3CH2- and CH3CH3CH3CH3

CH3CH3CH3CH2- is the base, as it can accept a proton to form CH3CH3CH3CH3. CH3CH3CH3CH3 cannot donate or accept a proton, it's neither acid nor base, but it's most represented as the conjugate acid in this exercise. The Lewis structures are: CH3CH3CH3CH2-: H - C - C - C - C- | | | H H H CH3CH3CH3CH3: H - C - C - C - C - H | | | H H H