What is the oxidation state of the underlined atom in the reaction: Mn(NO3)2 + 2 HCl --> MnCl2 + 2 HNO3
underlined is N in (NO3)2

+5

Explanation:

Let's consider the following balanced equation.

Mn(NO₃)₂ + 2 HCl --> MnCl₂ + 2 HNO₃

We can determine the oxidation number of N in (NO₃)₂²⁻ taking into account that the sum of the oxidation numbers of the elements present in a chemical species is equal to this overall charge. For this compound we know:

2 N + 6 O = 2-

2 N + 6 (-2) = 2-

2 N = +10

N = +5