What is the conjugate acid in the following reaction: [tex]$HCl ( aq )+$[/tex] [tex]$H _2 O ( i ) \rightarrow Cl ^{-}( aq )+ H _3 O ^{+}( aq ) ?$[/tex]
A. [tex]$H _2 O$[/tex]
B. [tex]$Cl ^{-}$[/tex]
C. [tex]$H _3 O ^{+}$[/tex]
Answer (2)
The conjugate acid in the given reaction is H3O+. This is because H2O acts as a base by accepting a proton from HCl and forms H3O+. Therefore, the correct choice is C: H3O+.
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Water ( H 2 O ) acts as a base and accepts a proton ( H + ).
Hydronium ion ( H 3 O + ) is formed when water accepts a proton.
The conjugate acid is H 3 O + .
Therefore, the conjugate acid in the reaction is H 3 O + .
Explanation
Identifying the Reaction In this reaction, we have hydrochloric acid ( H Cl ) reacting with water ( H 2 O ) to form chloride ions ( C l − ) and hydronium ions ( H 3 O + ). We need to identify the conjugate acid. Remember, a conjugate acid is formed when a base accepts a proton ( H + ).
Determining the Base In the given reaction, water ( H 2 O ) acts as a base by accepting a proton ( H + ) from hydrochloric acid ( H Cl ). When H 2 O accepts a proton, it forms the hydronium ion ( H 3 O + ).
Identifying the Conjugate Acid Therefore, the conjugate acid in this reaction is H 3 O + .
Final Answer The conjugate acid is the species formed when a base accepts a proton. In this case, H 2 O accepts a proton to form H 3 O + , so H 3 O + is the conjugate acid.
Examples
Understanding conjugate acids and bases is crucial in many chemical processes, including acid-base titrations. For instance, when determining the concentration of an unknown acid using a strong base, the formation of conjugate acid-base pairs helps to predict the pH changes during the titration. This knowledge is also vital in biological systems, where maintaining proper pH levels is essential for enzyme activity and overall cellular function. For example, the bicarbonate buffering system in blood relies on the interconversion of carbonic acid ( H 2 C O 3 ) and bicarbonate ions ( H C O 3 − ), a conjugate acid-base pair, to maintain blood pH within a narrow range.
