Which of the following reactions are redox reactions?

1. Al(s)+3Ag^+(aq)-->Al^3+(aq)+3Ag(s)
2. SO3(g)+H2O(l)-->H2SO4(aq)
3. Ba(s)+Cl2(g)-->BaCl2(s)
4. Mg(s)+Br2(l)-->MgBr2(s)

134 are redox

1,3,4

Determine the oxidation state of each element on both sides of the equation. Those that change oxidation state are either oxidized or reduced.

1. Well, let's see here! Al(s) is being oxidized to Al^3+(aq) and Ag^+(aq) is being reduced to Ag(s). Looks like we've got some electron shuffling going on, so it's a redox reaction!

2. SO3(g) reacts with H2O(l) to form H2SO4(aq). Although there is a rearrangement of atoms, I'm sorry to say that there's no electron transfer happening here. So, it's not a redox reaction. Bummer, right?

3. Ba(s) reacts with Cl2(g) to form BaCl2(s). I hate to be the bearer of bad news, but there's no electron transfer taking place, so it's not a redox reaction. Don't worry, though — I'll find a way to brighten your day!

4. Good news! Mg(s) is being oxidized to MgBr2(s) while Br2(l) is being reduced. Looks like electrons are getting passed around, so we've got a redox reaction on our hands.

So, the redox reactions are 1 and 4. Keep on rocking in the chemical world!

To determine which of the given reactions are redox reactions, we need to identify if there is any change in the oxidation states of the elements involved.

1. Al(s) + 3Ag+(aq) -> Al3+(aq) + 3Ag(s)
In this reaction, the oxidation state of aluminum (Al) changes from 0 to +3, and the oxidation state of silver (Ag) changes from +1 to 0. Therefore, this is a redox reaction.

2. SO3(g) + H2O(l) -> H2SO4(aq)
In this reaction, the oxidation states of sulfur (S) and oxygen (O) remain the same throughout the reaction. There is no change in the oxidation states of any elements involved. Therefore, this is not a redox reaction.

3. Ba(s) + Cl2(g) -> BaCl2(s)
In this reaction, the oxidation state of barium (Ba) remains the same (0) throughout the reaction, and the oxidation state of chlorine (Cl) also remains the same (-1). There is no change in the oxidation states of any elements involved. Therefore, this is not a redox reaction.

4. Mg(s) + Br2(l) -> MgBr2(s)
In this reaction, the oxidation state of magnesium (Mg) changes from 0 to +2, and the oxidation state of bromine (Br) changes from 0 to -1. Therefore, this is a redox reaction.

So, the redox reactions among the given options are:
1. Al(s) + 3Ag+(aq) -> Al3+(aq) + 3Ag(s)
4. Mg(s) + Br2(l) -> MgBr2(s)