How many ions are present if 2.0 moles of hno3 are completely dissolved in water?

Nitric acid(HNO3) is a strong acid so most of its component will dissociate into an ion form. When dissolved into water, nitric acid will have this reaction
HNO3= 1 H + NO3 

For every 1 mol of HNO3, there will be 1 mol of H+ ion and NO3- ion formed, which makes a total of 2 ions(degree of dissociation = 2). 
Then for 2 moles of HNO3 it would be: 2 moles * 2= 4 moles of ion