Hey there!
<span>Atomic Masses :
</span>
H = <span>1.00794 a.m.u
N = </span><span>14.0067 a.m.u
O = </span><span>15.9994 a.m.u
Therefore:
HNO3 = </span>1.00794 + 14.0067 + ( 15.9994 * 3 ) => <span>63.0128 g/mol</span>
3.45x-8.75 is the simplified version:)