Calcium trioxonitrate(V) is (CaNO\(_3\))\(_2\)

The molecular mass of CaNO\(_3\))\(_2\) =  40 + (14 + (16 X 3)) x 2 = 164

Relative molecular mass of nitrogen(N\(_2\)) = 14 x 2 = 28

% by mass of nitrogen in CaNO\(_3\))\(_2\) = \(\frac{28}{164}\) x \(\frac{100}{1}\)

  = 17.073 ≈ 17.1%