ANSWER
The molarity of HNO3 is 0.8 M
Step-by-step explanation
Given that
The volume of HNO3 is 3.5L
The number of moles of HNO3 is 2.8
To find the molarity of HNO3, follow the steps below
Molarity is defined as the mole of solute per unit volume of the solution.

Hence, the molarity of HNO3 is 0.8 M