Question

Methoxide ion, \(\mathrm{CH}_{3} \mathrm{O}^{-}\), and amide ion, \(\mathrm{NH}_{2}^{-}\), are very strong bases that are "leveled" by water. What does this mean? Write the reactions that occur in the leveling process. What species do the two leveled solutions have in common?

Short answer

The leveling effect makes both methoxide ion and amide ion form hydroxide ions in water. The common species in both leveled solutions is \(\mathrm{OH}^{-}\).

Step-by-step solution

Understand the Concept of Leveling Effect

The leveling effect occurs when a strong base, which is stronger than the conjugate base of the solvent (in this case, water), reacts with the solvent to produce its conjugate base. Essentially, all strong bases will be leveled to the strength of the solvent's conjugate base.

Identify the Reactions for Methoxide Ion

The methoxide ion \(\mathrm{CH}_3 \mathrm{O}^{-}\) reacts with water. The reaction can be written as: \[\mathrm{CH}_3 \mathrm{O}^{-} + \mathrm{H}_2\mathrm{O} \rightarrow \mathrm{CH}_3\mathrm{OH} + \mathrm{OH}^{-}\] This shows methoxide turning into methanol and producing hydroxide ion \(\mathrm{OH}^{-}\).

Identify the Reactions for Amide Ion

The amide ion \(\mathrm{NH}_2^{-}\) reacts with water. The reaction can be written as: \[\mathrm{NH}_2^{-} + \mathrm{H}_2\mathrm{O} \rightarrow \mathrm{NH}_3 + \mathrm{OH}^{-}\] This shows amide turning into ammonia and producing hydroxide ion \(\mathrm{OH}^{-}\).

Determine Common Species in the Leveled Solutions

Both the reactions produce \(\mathrm{OH}^{-}\) ions when the strong bases react with water. Therefore, \(\mathrm{OH}^{-}\) (hydroxide ion) is the common species in both leveled solutions.

Key concepts

Strong Bases

Strong bases are chemical compounds that are highly efficient at accepting protons.
Some common examples include methoxide ion (\(\text{CH}_3\text{O}^{-}\)) and amide ion (\(\text{NH}_2^{-}\)).
These bases are significantly stronger than the conjugate base of water, which is the hydroxide ion \(\text{(OH}^{-}\)).
Because of their strength, these bases can completely react with water. This means they will readily donate electrons and form their respective conjugate acids.
For example:

• The methoxide ion (\(\text{CH}_3\text{O}^{-})\) reacts with water to form methanol (\(\text{CH}_3\text{OH}\)) and \(\text{OH}^{-}\).
• The amide ion (\(\text{NH}_2^{-}\)) reacts with water to form ammonia (\(\text{NH}_3\)) and \(\text{OH}^{-}\).

The constant production of \(\text{OH}^{-}\) in these reactions shows just how potent these strong bases are when mixed with water.

Conjugate Acids and Bases

In acid-base chemistry, every acid has a conjugate base and every base has a conjugate acid.
When a strong base like methoxide or amide reacts with water, they produce their respective conjugate acids due to the leveling effect.

• Methoxide (\(\text{CH}_3\text{O}^{-}\)) turns into methanol (\(\text{CH}_3\text{OH}\)).
• Amide (\(\text{NH}_2^{-}\)) turns into ammonia (\(\text{NH}_3\)).

These products are the conjugate acids of the strong bases.
The water in these reactions donates a proton (\(\text{H}^+\)), forming a \(\text{OH}^{-}\) ion, which is the conjugate base of water.
The newly formed conjugate bases (\(\text{OH}^{-}\)) are less reactive compared to the original strong bases.

• This process of formation of weaker bases (\(\text{OH}^{-}\)) from strong bases is what essentially brings about the leveling effect.
• It means that no matter the strength of the base added, the water levels them to the \(\text{OH}^{-}\) ion in basicity.

This concept of conjugate acids and bases helps us understand the pairing and balancing in acid-base reactions.

Acid-Base Reactions

Acid-base reactions are fundamental chemical reactions where an acid donates a proton (H+) to a base.
In these reactions, the products include a conjugate base and a conjugate acid. The leveling effect comes into play during these reactions when strong bases react with water.
For instance:

• The methoxide ion \(\text{CH}_3\text{O}^{-}\) reacts with water \(\text{H}_2\text{O}\), producing methanol \(\text{CH}_3\text{OH}\) and hydroxide ion \(\text{OH}^{-}\).
• Amide ion \(\text{NH}_2^{-}\) reacts with water \(\text{H}_2\text{O}\), producing ammonia \(\text{NH}_3\) and hydroxide ion \(\text{OH}^{-}\).

Both reactions show how strong bases are leveled by water, leading to the formation of \(\text{OH}^{-}\) ions.
This commonality in the reactions is key in understanding the equilibrium and balancing of reactions in aqueous solutions. Due to its high reactivity and ability to fully dissociate in water, strong bases always result in conjugate acids and hydroxide ions.
This behavior reflects the intrinsic principles of acid-base reactions and helps emphasize the powerful leveling effect in chemistry.