Proton Donor
In acid-base chemistry, a proton donor is considered the acid. An acid donates a proton \(( \text{H}^+ \)) to another species. For example, in the reaction of acetic acid ( \(\text{CH}_3\text{COOH} \)) with water ( \(\text{H}_2\text{O} \)), \(\text{CH}_3\text{COOH} \) is the proton donor as it gives up an \(\text{H}^+ \) ion to \(\text{H}_2\text{O} \), forming hydronium ( \(\text{H}_3\text{O}^+ \)) and acetate ( \(\text{CH}_3\text{COO}^- \)). Similarly, bicarbonate ( \(\text{HCO}_3^- \)) donates a proton to water forming carbonic acid ( \(\text{H}_2\text{CO}_3 \)) in another reaction. In the case of nitric acid reacting with sulfate, \(\text{HNO}_3 \) donates a proton to \(\text{SO}_4^{2-} \) to produce \(\text{HSO}_4^- \) and \(\text{NO}_3^- \).
Proton Acceptor
A proton acceptor is also known as a base in acid-base reactions. A base accepts a proton \(( \text{H}^+ \)) from an acid. For instance, in the reaction where water acts as a proton acceptor from acetic acid, water \(( \text{H}_2\text{O} \)) accepts an \(\text{H}^+ \) ion from \(\text{CH}_3\text{COOH} \), resulting in the formation of hydronium ion \(( \text{H}_3\text{O}^+ \)). Likewise, in a bicarbonate-water reaction, water acts as the proton acceptor forming hydroxide ion \(( \text{OH}^- \)). In the nitric acid and sulfate reaction, \(\text{SO}_4^{2-} \) accepts a proton to form \(\text{HSO}_4^- \).
Conjugate Acid-Base Pair
In acid-base reactions, every acid has a conjugate base, and every base has a conjugate acid. The conjugate base is what remains after the acid donates a proton, while the conjugate acid is what forms when the base accepts a proton. For example, when \(\text{CH}_3\text{COOH} \) (acetic acid) donates a proton, it becomes \(\text{CH}_3\text{COO}^- \) (acetate), its conjugate base. When water \(( \text{H}_2\text{O} \)) accepts a proton, it becomes \(\text{H}_3\text{O}^+ \) (hydronium), its conjugate acid. Similarly, \(\text{HCO}_3^- \) (bicarbonate) turns into \(\text{CO}_3^{2-} \) after donating a proton, and water turns into \(\text{OH}^- \) after accepting a proton. In the reaction involving \(\text{HNO}_3 \) (nitric acid), its conjugate base is \(\text{NO}_3^- \), while \(\text{HSO}_4^- \) is the conjugate acid of \(\text{SO}_4^{2-} \).
Acetic Acid
Acetic acid ( \(\text{CH}_3\text{COOH} \)) is a common weak acid found in vinegar. When acetic acid reacts with water, it donates a proton forming its conjugate base, acetate \(\text{CH}_3\text{COO}^- \). In this reaction, the water molecule acts as the base, accepting the proton and forming hydronium ion \(\text{H}_3\text{O}^+ \). Acetic acid's role in many biochemical processes and its presence in daily life makes it an important substance to understand. Its chemical structure allows it to donate a proton, typical of weak acids, which only partially ionize in solution.
Bicarbonate
Bicarbonate ion \(\text{HCO}_3^- \) plays a key role in maintaining the pH balance in blood and other bodily fluids. In water, bicarbonate can react as an acid by donating a proton, forming carbonic acid \(\text{H}_2\text{CO}_3 \), or as a base by accepting a proton, resulting in carbonate \(\text{CO}_3^{2-} \). This dual capability makes bicarbonate a crucial buffer in physiological systems. For example, in the given reaction, \(\text{HCO}_3^- \) donates a proton to \(\text{H}_2\text{O} \), forming carbonic acid and \(\text{OH}^- \). This reversible reaction helps regulate pH by neutralizing acids and bases.
Nitric Acid
Nitric acid ( \(\text{HNO}_3 \)) is a strong acid commonly used in laboratory and industrial applications. It readily donates a proton to bases. When nitric acid reacts with \(\text{SO}_4^{2-} \) (sulfate ion), it donates a proton to form \(\text{HSO}_4^- \) (bisulfate) and \(\text{NO}_3^- \) (nitrate ion). Since nitric acid is a strong acid, it completely ionizes in solution, meaning it fully dissociates to release its \(\text{H}^+ \) ions. This characteristic is important in reactions that require a strong protic environment and explains its prominence in various chemical processes.
