Sunday

April 20, 2014

April 20, 2014

Posted by **Amy** on Monday, June 20, 2011 at 7:22am.

Use oxidation numbers to identify if this reaction is REDOX reactions.

3NO2(g) + H2O(l) �� 2HNO3(aq) + NO(g)

3NO2 = -3 for N

= -2 for o2

H2O = +1 for H2

= -2 for O

---->

2HNO3 = +1 for 2H

= -3 for N

= -2 for O3

NO = -3 for N

= -2 for O

Therefore Nitrogen is reduced (one -3 remains on right side)

hence REDOX has occured

Is this right? Also should I be multiplying oxidation numbers if there is a number in front ie. 2SO = -2 oxidation but should I multiply by the 2 infront so is now -4 oxidation for sulphur in 2SO? Please let me know because I haven't done this and if wrong need to correct for a lot of questions :(

- Chemistry -
**DrBob222**, Monday, June 20, 2011 at 3:40pmWhat you have done confuses me; in a class I could ask a question or two and know how to answer.

The first equation is redox so you are correct; however, not for the reason you cite(-3 N left over on one side versus the other).

The oxidation state for N in NO2 is +4 and not -3. How do you get that? Each O is -2 and there are two of them for a total of -4; therefore, for NO2 to be zero N must be +4. On the right side, each N is +5 in HNO3 and +2 in NO. This is a redox equation because you have something being oxidized and something being reduced (in this case it just happens to be N in NO2---it goes both ways).

As to multiplying by the coefficient, it depends. To identify if redox has occurred, you want to see that EACH atom has changed and I don't multiply by the coefficient to determine that since it isn't needed. In fact, it can be confusing in some situations (such as this one).

So when do I multiply by the coefficient? When I am balancing equations, we want to know the TOTAL charge on side going to a TOTAL charge on the other. In the example you cite for 2SO, here are the two ways of doing it.

#1. Each O is -2, for SO to be zero then S must be +2.

#2. Each O is -2 and that x 2 = -4 for both O atoms. Therefore, both S atoms must be +4 or EACH must be +2. Doing it this way just increases the number or steps (the work) AND the chance of making a mistake.

**Related Questions**

Math Riddle - What day would yesterday be if Wednesday was five days before the ...

math 140 - I have two questions posted that has not been answered please help. ...

Intro. to Comp. - Would you please go to page 2 and look under "intro. to comp...

whats going on? - Hi. I posted both the questions about batteries and volatic ...

MATH, 3rd time i posted this - can someone please help me, i posted this like 3 ...

social 10 COULD SOMEONE PLEASE HELP ME! - Historical Globalization & IMPERIALISM...

Romeo and Juliet Help (24 hours and no response) - I posted questions yesterday ...

Chemistry - How do the qualities of acids and bases help us in the natural world...

Repost physics - PLEASE SOMEONE HELP ME!! I POSTED DOWN AT AROUND 10 something...

Chemistry - I posted a question at 5:43pm yesterday...can anyone please help ...