What is the [OH^-] if the pH is 4.900

A.(nh4)(2co3)is the correct answer 

The answer to your question would be c. mineral oil  

(no3)⁻n has oxidation number x,o has oxidation number -2.(x*1 -2*3) charge of the nitrate ion, and we know that charge of the nitrate ion =-1.so,(x*1 -2*3) =-1x-6=-1x=+5answer a. +5.

Answer///precipitate;