When does a star reach equilibrium?

1. Gravity pulls gas and dust towards the core.
2. Inside the core, temperature increases as gas atom collisions increase.
3. Density of the core increases as more and more atoms try to share the same space. 
4. Gas pressure increases as atomic collisions and density [atoms & space] increase.
5. The protostar's  gas pressure resists the collapse of the nebula. 
6. When the gas pressure [equals gravity] the protostar has reached equilibrium and accretion comes to a stop.

(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.