Identify the correct acid/conjugate base pair in this equation:
HCO3- is an acid and OH- is its conjugate base.
H2O is an acid and HCO3- is its conjugate base.
H2O is an acid and H2CO3 is its conjugate base.
HCO3- is an acid and H2CO3 is its conjugate base.
H2O is an acid and OH- is its conjugate base.
The correct answer and explanation is :
The correct acid/conjugate base pair in this equation is:
H2O is an acid and OH- is its conjugate base.
Explanation:
To understand the correct acid/conjugate base pair, we need to review the concept of acids and bases in terms of Brønsted-Lowry theory, which defines acids as proton (H⁺) donors and bases as proton acceptors.
- H2O is an acid and OH- is its conjugate base:
- In this case, water (H2O) can act as an acid. When water donates a proton (H⁺), it becomes hydroxide (OH⁻), its conjugate base. The reaction can be written as:
[
H_2O \rightarrow H^+ + OH^-
]
Here, H₂O donates a proton (H⁺) to form OH⁻, so H₂O is the acid and OH⁻ is the conjugate base.
- HCO3⁻ is an acid and OH⁻ is its conjugate base:
- This statement is incorrect because bicarbonate (HCO₃⁻) is not donating a proton in this case. In fact, HCO₃⁻ can act as both an acid and a base, but it is not donating a proton to form OH⁻. HCO₃⁻ would donate a proton to form CO₃²⁻ (carbonate), not OH⁻.
- H2O is an acid and HCO3⁻ is its conjugate base:
- This is incorrect. H2O cannot donate a proton to form HCO3⁻. In this context, HCO₃⁻ does not act as the conjugate base of H2O.
- H2O is an acid and H2CO3 is its conjugate base:
- This is incorrect because H2CO3 (carbonic acid) is not the conjugate base of H2O. In fact, H2CO3 would be a donor of a proton, not a product of H2O losing a proton.
- HCO3⁻ is an acid and H2CO3 is its conjugate base:
- This is incorrect because the conjugate base of H2CO3 is HCO3⁻ (not the other way around). HCO3⁻ can donate a proton to form CO₃²⁻.
Thus, the correct pair is H2O as an acid and OH⁻ as its conjugate base, based on the proton transfer mechanism in acid-base reactions.