Saturday, September 29, 2007

Chemistry Questions - Redox Reaction

How about another Chemistry Question on Redox Reactions as a food for thoughts over the weekend...

Q) Which of the following conversions is a redox reaction (involves oxidation/reduction)?

A)H+ => H20
B)NO2 => NO3^-
C)SO2 => SO3^2-
D)SO3 => SO4^2-

Enjoy and take care.



zhengning said...

I'll give this question a try.

A)H+ => H20

The oxidation state(number) of H is +1. To find the oxidation state of H in H2O, form eqn: 2H + (-2) = 0
Hence, oxidation state of H in H2O is +1.
A is not the answer.

B)NO2 => NO3^-
Find the oxidation state of N in NO2 and NO3^-.

Eqn: N + (-2 X 2) = 0
N in NO2 = +4

Eqn: N + (-2 X 3) = -1
N in NO3^- = +5

This could be the answer.

C)SO2 => SO3^2-
Find the oxidation state of S in SO2 and SO3^2-.

Eqn: S + (-2 X 2) = +4
S in SO2 = +4

Eqn: S + (-2 X 3) = -2
S in SO3^- = +4

C is not the answer.

D)SO3 => SO4^2-
Similarly, we will get +6 for S in both SO3 and SO4^2-

So.... (B) is the answer.

Sean Chua said...

Well Done Zhengning! You are Right!

This is exatly the approach in answering such question testing on the Oxidation States/Numbers.

Do share this with your friends, siblings and peers alike.

PS: Good for you to type out the detailed working and share with all.