Which one of the following is NOT a Lewis acid-base reaction?

1. ) Ca + S --> Ca2+ + S2-
2. ) BeF2 + 2 F- --> BeF42-
3. ) H+ + -O-H --> H-O-H
4. ) NH3 + BF3 --> H3N-BF3

i thought it was 1...but im not sure...but i know that 3 & 4 are definatly right.

In Lewis acid-base reactions, a Lewis acid (electron acceptor) reacts with a Lewis base (electron donor) to form a coordinate covalent bond. Let's analyze each option:

1. Ca + S --> Ca2+ + S2-
In this reaction, calcium (Ca) loses two electrons to become Ca2+, and sulfur (S) gains two electrons to become S2-. This is an example of an ionic bond formation, not a Lewis acid-base reaction.

2. BeF2 + 2 F- --> BeF42-
In this reaction, beryllium fluoride (BeF2) reacts with two fluoride ions (F-) to form a complex ion, BeF42-. This is a Lewis acid-base reaction, as beryllium (Be) accepts the lone pair of electrons from the fluoride ion (F-).

3. H+ + -O-H --> H-O-H
This reaction involves a hydrogen ion (H+) reacting with a hydroxide ion (-OH) to form water (H2O). This is a classic example of a Lewis acid-base reaction, where the hydrogen ion acts as a Lewis acid and accepts a pair of electrons from the hydroxide ion, which acts as a Lewis base.

4. NH3 + BF3 --> H3N-BF3
In this reaction, ammonia (NH3) reacts with boron trifluoride (BF3) to form an adduct, H3N-BF3. This is also a Lewis acid-base reaction because the lone pair of electrons on the nitrogen atom (N) donates to the boron atom (B) in the BF3 molecule.

Therefore, the correct answer is option 1. Ca + S --> Ca2+ + S2-, which is not a Lewis acid-base reaction.

To determine which one of the given reactions is NOT a Lewis acid-base reaction, we need to understand what a Lewis acid-base reaction is.

In a Lewis acid-base reaction, a Lewis acid accepts an electron pair (acts as an electron acceptor), while a Lewis base donates an electron pair (acts as an electron donor).

Let's analyze each reaction:

1. Ca + S → Ca2+ + S2-
In this reaction, calcium (Ca) donates two electrons to sulfur (S), forming calcium cation (Ca2+) and sulfur anion (S2-). Hence, this reaction involves the transfer of electrons and can be considered a Lewis acid-base reaction.

2. BeF2 + 2 F- → BeF42-
In this reaction, beryllium fluoride (BeF2) reacts with fluoride ions (F-) to form beryllium tetrafluoride (BeF42-). Here, beryllium (Be) accepts electron pairs from two fluoride ions, making it a Lewis acid, while fluoride ions act as Lewis bases by donating their electron pairs. Thus, this reaction is a Lewis acid-base reaction.

3. H+ + -O-H → H-O-H
This reaction represents the dissociation of water (H2O). Here, the hydronium ion (H+) accepts a lone pair of electrons from a water molecule (-O-H), forming a water molecule (H-O-H). This is a classic example of a Lewis acid-base reaction.

4. NH3 + BF3 → H3N-BF3
In this reaction, ammonia (NH3) donates a lone pair of electrons to boron trifluoride (BF3), forming a coordinate covalent bond and resulting in the formation of a complex molecule called a Lewis acid-base adduct. Therefore, this reaction is also a Lewis acid-base reaction.

Based on our analysis, all of the given reactions (1, 2, 3, and 4) are Lewis acid-base reactions. So, none of them is the correct answer to the question "Which one of the following is NOT a Lewis acid-base reaction?"

It seems there is an error in your understanding or the options provided.

In #2, the two F- ions are "donating" electron pairs to the Be atom in forming covalent bonds with Be. That makes F- a Lewis base and the Be atom a Lewis acid. In #1 there is a transfer of electrons from Ca to S in forming two ions. No covalent bonds are formed. Is that consistent with your answer?