Question

which of the following substances is a brønsted-lowry acid?
○ $\ce{co_3^{2-}(aq)}$
○ $\ce{ch_3coo^-(aq)}$
○ $\ce{h_2s(aq)}$
○ $\ce{c_6h_5nh_2(aq)}$
○ none of the above
question 28 (1 point)
which of the following substances can act as a brønsted-lowry base?
○ $\ce{hclo_4(aq)}$
○ $\ce{hocl(aq)}$
○ $\ce{h_2o(l)}$
○ $\ce{h_3o^+(aq)}$
○ none of the above

Explanation:

First Question (Brønsted - Lowry acid)

Step1: Recall Brønsted - Lowry acid definition

A Brønsted - Lowry acid is a substance that donates a proton ($\ce{H+}$).

Step2: Analyze each option

• $\ce{CO3^{2 - }(aq)}$: Carbonate ion, it accepts protons (acts as a base), e.g., $\ce{CO3^{2 - } + H+ -> HCO3-}$.
• $\ce{CH3COO-(aq)}$: Acetate ion, accepts protons (base), $\ce{CH3COO- + H+ -> CH3COOH}$.
• $\ce{H2S(aq)}$: Hydrogen sulfide can donate a proton, e.g., $\ce{H2S <=> H+ + HS-}$, so it is a Brønsted - Lowry acid.
• $\ce{C6H5NH2(aq)}$: Aniline, accepts protons (base), $\ce{C6H5NH2 + H+ -> C6H5NH3+}$.
• "none of the above" is incorrect as $\ce{H2S}$ is an acid.

Step1: Recall Brønsted - Lowry base definition

A Brønsted - Lowry base is a substance that accepts a proton ($\ce{H+}$).

Step2: Analyze each option

• $\ce{HClO4(aq)}$: Perchloric acid, donates a proton (acid), $\ce{HClO4 -> H+ + ClO4-}$.
• $\ce{HOCl(aq)}$: Hypochlorous acid, donates a proton (acid), $\ce{HOCl <=> H+ + OCl-}$.
• $\ce{H2O(l)}$: Water can accept a proton (acts as a base), $\ce{H2O + H+ -> H3O+}$, and also donate a proton (acts as an acid), $\ce{H2O <=> H+ + OH-}$. So it can act as a base.
• $\ce{H3O+(aq)}$: Hydronium ion, donates a proton (acid), $\ce{H3O+ -> H+ + H2O}$.
• "none of the above" is incorrect as $\ce{H2O}$ can act as a base.

Answer:

$\ce{H2S(aq)}$ (the option with $\ce{H2S(aq)}$)

Second Question (Brønsted - Lowry base)