To determine which of the following reactions shows a Bronsted-Lowry acid reacting, we need to recall the definition of a Bronsted-Lowry acid and base. In the Bronsted-Lowry theory:
- An acid is a species that donates a proton (H+).
- A base is a species that accepts a proton (H+).
Now, let us analyze each reaction:
1. Reaction: [tex]\( CO + NO _2 \rightarrow CO _2 + NO \)[/tex]
In this reaction, there is no transfer of a proton (H+). The reaction involves the transfer of oxygen atoms and does not fit the definition of Bronsted-Lowry acid-base reaction where a proton is exchanged.
2. Reaction: [tex]\( NH _3 + H ^{+} \rightarrow NH _4^{+} \)[/tex]
In this reaction, the ammonia (NH3) molecule is accepting a proton (H+) to form ammonium (NH4+). Thus, NH3 is acting as a Bronsted-Lowry base because it accepts a proton. However, since we're looking for a reaction where an acid is reacting, this is not the correct reaction.
3. Reaction: [tex]\( CO _3^{2-} + H ^{+} \rightarrow HCO _3^{-} \)[/tex]
In this reaction, the carbonate ion (CO3^2-) is accepting a proton (H+) to form the bicarbonate ion (HCO3^-). Therefore, the carbonate ion acts as a Bronsted-Lowry base because it accepts a proton. This reaction also does not show an acid reacting.
4. Reaction: [tex]\( HCl + H _2 O \rightarrow H _3 O ^{+} + Cl ^{-} \)[/tex]
In this reaction, hydrochloric acid (HCl) is donating a proton (H+) to water (H2O) to form hydronium ion (H3O+) and chloride ion (Cl^-). Here, HCl is donating a proton, thus acting as a Bronsted-Lowry acid.
Given that we are looking for a reaction where a Bronsted-Lowry acid (a proton donor) is reacting, the correct reaction is:
[tex]\[ \boxed{HCl + H _2 O \rightarrow H _3 O ^{+} + Cl ^{-}} \][/tex]
So, the correct option is:
Option 4: [tex]\( HCl + H _2 O \rightarrow H _3 O ^{+} + Cl ^{-} \)[/tex]
Therefore, the reaction that shows a Bronsted-Lowry acid reacting is option 4.
