First we need the molar mass of NaNO_3:-
[tex]\\ \sf\longmapsto 23+14+3(16)[/tex]
[tex]\\ \sf\longmapsto 37+48[/tex]
[tex]\\ \sf\longmapsto 85g/mol[/tex]
Now we need moles of NaNO_3
[tex]\\ \sf\longmapsto No\:of\:moles=\dfrac{Given\:mass}{Molar\:mass}[/tex]
[tex]\\ \sf\longmapsto No\:of\:moles=\dfrac{65}{85}[/tex]
[tex]\\ \sf\longmapsto No\:of\:moles=0.765mol[/tex]
Now
[tex]\\ \sf\longmapsto Molarity=\dfrac{Moles\:of\:solute}{Vol\:of\:soln.\:in\:L}[/tex]
[tex]\\ \sf\longmapsto Molarity=\dfrac{0.765}{0.350}[/tex]
[tex]\\ \sf\longmapsto Molarity=2.2M[/tex]
