Great question! To determine which definition is correct for a Brønsted-Lowry base, let's review the fundamental concepts of acid-base chemistry according to the Brønsted-Lowry theory.
The Brønsted-Lowry theory defines acids and bases based on their ability to donate or accept protons (H⁺ ions):
- A Brønsted-Lowry acid is a substance that donates a proton (H⁺) to another substance.
- A Brønsted-Lowry base is a substance that accepts a proton (H⁺) from another substance.
Now, let's evaluate each option in the context of this theory:
1. Increases [tex]\([H^+]\)[/tex] when placed in water:
- This is typically a characteristic of a substance that donates protons, thereby increasing the concentration of [tex]\(H^+\)[/tex] ions in water. This describes a Brønsted-Lowry acid, not a base.
2. Decreases [tex]\([H^+]\)[/tex] when placed in water:
- This describes a substance that would neutralize or accept [tex]\(H^+\)[/tex] ions, thus reducing their concentration in water. This does align with the behavior of a base, although it is not the most precise definition according to the Brønsted-Lowry theory.
3. Acts as a proton donor in any system:
- Donating a proton is the characteristic behavior of a Brønsted-Lowry acid, not a base.
4. Acts as a proton acceptor in any system:
- This directly fits the definition of a Brønsted-Lowry base, which is a substance that accepts a proton.
Based on this analysis, the correct definition for a Brønsted-Lowry base is:
"A Brønsted-Lowry base is defined as a substance which acts as a proton acceptor in any system."
Thus, the correct option is:
(4) acts as a proton acceptor in any system.
