To determine which of the given substances is an example of a Bronsted-Lowry base, we need to understand the definition of a Bronsted-Lowry base. A Bronsted-Lowry base is a substance that can accept a proton (H⁺).
Let's evaluate each of the given options:
A. HCl
- HCl (hydrochloric acid) is a strong acid. In aqueous solution, it dissociates into H⁺ and Cl⁻. It donates a proton (H⁺) and, therefore, acts as a Bronsted-Lowry acid, not a base.
B. [tex]\( H_3O^+ \)[/tex]
- [tex]\( H_3O^+ \)[/tex] (hydronium ion) is the form that H⁺ takes in water. It is typically considered an acid because it can donate a proton to other species, reverting back to water [tex]\( H_2O \)[/tex]. Hence, it acts as a Bronsted-Lowry acid.
C. [tex]\( NH_3 \)[/tex]
- [tex]\( NH_3 \)[/tex] (ammonia) is a molecule that has a lone pair of electrons on the nitrogen atom. This lone pair allows [tex]\( NH_3 \)[/tex] to accept a proton and form [tex]\( NH_4^+ \)[/tex] (ammonium ion). Therefore, [tex]\( NH_3 \)[/tex] acts as a Bronsted-Lowry base by accepting a proton.
D. [tex]\( NH_4^+ \)[/tex]
- [tex]\( NH_4^+ \)[/tex] (ammonium ion) is the conjugate acid of ammonia [tex]\( NH_3 \)[/tex]. It can donate a proton to revert back to [tex]\( NH_3 \)[/tex]. Thus, it acts as a Bronsted-Lowry acid.
From our evaluations, only [tex]\( NH_3 \)[/tex] (ammonia) is capable of accepting a proton, making it a Bronsted-Lowry base. Therefore, the correct answer is:
C. [tex]\( NH_3 \)[/tex]
