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The Oxidation State of Nitrogen Is Most Positive In Which Compound?

August 16, 2019

 

 

The Oxidation State of Nitrogen Is Most Positive In Which Compound?

 

This is an SAT Chemistry question from 1998 SAT Chemistry test.

 

a. NO3^-1

b. NO2^-1

c. N2O

d. N2

e. NH3

 

Answer and Explanation:

Lets first go over some rules for assigning the oxidation number.

  • Free element has an oxidation number of 0. For example, O2, Fe, Cl2 etc all have oxidation numbers of zero. Therefore, nitrogen in choice d has an oxidation number of 0

  • All oxidation numbers in a neutral compound add up to 0. For example, lets solve N2O. Oxygen has an oxidation number of -2 as can be seen on the periodic table (group 16 is mostly -2 oxidation number). Lets now make an equation since we dont know nitrogen, we will make it x. 2x+ (-2) = 0. Therefore, x=+1. Let's solve choice e the same way. Hydrogen is +1 unless with a metal. Thus, we get x+1*3=0,    x= -3. Choice e can be eliminated.

  • All oxidation number of a charged compound must add up to its charge. Lets now solve choices a and b. Choice a's equation becomes x+(-2*3)= -1 x=+5  Choice b is x+(-2*2)= -1 x=+4. We can now see that choice A must be the correct answer since it gave us positive five charge for the nitrogen.

For more help with chemistry and organic chemistry, our founder and tutor Mayya is available to help. She is an Honors NYU graduate in chemistry and psychology. She also has been tutoring chemistry for the past 9 years with amazing results. Mayya is available for tutoring in Brooklyn, Manhattan and online. Please call 646-407-9078 for more information. 

 

 

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