Question

Each molecule or ion can function as a base. Write a structural formula of the conjugate acid formed by reaction of each with \(\mathrm{HCl}\). (a) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{OH}\) (b) \(\mathrm{HCH}\) (c) \(\left(\mathrm{CH}_{3}\right)_{2} \mathrm{NH}\) (d) \(\mathrm{HCO}_{3}^{-}\)

Short answer

(a) CH3CH2OH, (b) HCH, (c) (CH3)2NH, (d) HCO3⁻. Answer: The structural formulas of the conjugate acids are (a) CH3CH2OH₂⁺, (b) H3C⁺, (c) (CH3)2NH₂⁺, and (d) H2CO3.

Step-by-step solution

Identify the Proton-Accepting Atom

For each molecule or ion, we need to find the atom with an unshared electron pair or a negative charge that can accept a proton (H⁺) from HCl. This will usually be nitrogen, oxygen, or sulfur.

Write the Structural Formula for the Conjugate Acid of CH3CH2OH

For (a) CH3CH2OH, the oxygen atom is the one with two unshared electron pairs that can accept a proton. Adding a proton to the oxygen atom gives the structural formula for the conjugate acid: CH3CH2OH₂⁺.

Write the Structural Formula for the Conjugate Acid of HCH

For (b) HCH or H2C, the carbon atom has two unshared electron pairs that can accept a proton. Adding a proton to the carbon atom gives the structural formula for the conjugate acid: H2C—H⁺, or H3C⁺.

Write the Structural Formula for the Conjugate Acid of (CH3)2NH

For (c) (CH3)2NH, the nitrogen atom has one unshared electron pair that can accept a proton. Adding a proton to the nitrogen atom gives the structural formula for the conjugate acid: (CH3)2NH₂⁺.

Write the Structural Formula for the Conjugate Acid of HCO3⁻

For (d) HCO3⁻, the oxygen atom with the negative charge has one unshared electron pair that can accept a proton. Adding a proton to this oxygen atom gives the structural formula for the conjugate acid: H2CO3. The structural formulas of the conjugate acids for each molecule/ion are as follows: (a) CH3CH2OH₂⁺ (b) H3C⁺ (c) (CH3)2NH₂⁺ (d) H2CO3