What is the conjugate base that is formed when carbonic acid is dissolved in water?
A. $H _3 O ^{+}$
B. $HCO _3^{-}$
C. $CO _3{ }^{2-}$
Answer (2)
When carbonic acid is dissolved in water, it donates a proton and forms the conjugate base bicarbonate ( H C O 3 − ). The dissociation reaction can be represented as H 2 C O 3 + H 2 O ⇌ H 3 O + + H C O 3 − . Thus, the correct answer is option B: H C O 3 − .
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Carbonic acid ( H 2 C O 3 ) donates a proton ( H + ) when dissolved in water.
The conjugate base is formed by removing a proton from the acid.
The dissociation reaction is: H 2 C O 3 + H 2 O ⇌ H 3 O + + H C O 3 − .
The conjugate base of carbonic acid is H C O 3 − .
Explanation
Understanding Conjugate Bases When carbonic acid ( H 2 C O 3 ) dissolves in water, it acts as an acid and donates a proton ( H + ) to water. The conjugate base is what remains after the acid loses this proton.
Dissociation Reaction The dissociation reaction of carbonic acid in water is: H 2 C O 3 + H 2 O ⇌ H 3 O + + H C O 3 −
Identifying the Conjugate Base In this reaction, carbonic acid ( H 2 C O 3 ) donates a proton to water ( H 2 O ), forming hydronium ion ( H 3 O + ) and bicarbonate ion ( H C O 3 − ). The bicarbonate ion ( H C O 3 − ) is the conjugate base of carbonic acid.
Conclusion Therefore, the conjugate base formed when carbonic acid is dissolved in water is H C O 3 − .
Examples
Understanding conjugate bases is crucial in many real-world applications, such as in buffer solutions that maintain a stable pH in biological systems. For example, the bicarbonate buffer system in our blood, involving carbonic acid and its conjugate base bicarbonate, helps to regulate the blood's pH, ensuring that our bodily functions operate correctly. This system works by neutralizing excess acids or bases in the blood, preventing drastic changes in pH that could be harmful. The equilibrium between carbonic acid ( H 2 C O 3 ) and bicarbonate ( H C O 3 − ) is essential for maintaining this balance, showcasing the practical importance of acid-base chemistry in everyday life.
