Here's some background information for the question:
Considering a redox reaction, it's either a gain/lose in oxygen, hydrogen, electron, or the increase/decrease in oxidation numbers. As the reaction given above does not contain any oxygen or hydrogen, plus a few reactants/products involves covalently bonded substances, it's best to solve the question by figuring out their change in oxidation numbers.
Basically, each element in either their compound or in their element itself has an assigned oxidation number. As redox reaction means both oxidation and reduction reaction taking place at the same time, <u>oxidation involves an increase in oxidation number of an element in a substance,</u> while r<u>eduction involves a decrease in oxidation number of an element in a substance.</u>
Speaking of assigning oxidation numbers, these are the rules that will be used in the question (though there are a lot more):
- Oxidation number of elements in free state itself is 0 (e.g. Cl2, O2, Cu etc.)
- The oxidation number of simple ions (e.g. in ionic compounds) is equal to the charge of the ion itself
Here's the most important part:
Let's look at the equation.
Cl2 (g), is a free element by itself, so the oxidation number for it is 0.
NaBr, Na ion has a charge of 1+ normally, thus Na's oxidation number is +1. (we put the +/- sign in front of the number). Br ion has a charge or 1-, therefore its oxidation number is -1.
NaCl, similar to the one above, Na ion has a 1+ charge, so it's oxidation number is +1. Cl ion has a charge of 1-, so it's oxidation number is -1.
Lastly, Br2, it is a free state element, so Br's oxidation number is 0.
Both Br and Cl has a change in oxidation number in the reaction.
The oxidation number of Br has increased from -1 in NaBr to 0 in Br2, therefore oxidation occurred.
The oxidation number of Cl has decreased from 0 in Cl2 to -1 in NaCl, therefore reduction has occurred.
We can determine this is a redox reaction.
For the second part of the question, we can see bromine has been oxidized while chlorine has been reduced considering their change in oxidation number.
