Answer
$Mr(O)= 16amu$
Work Step by Step
1. The mass of the carbon atom is 12 amu.
$Mr(N)= \frac{Mr(C)\times7}{6}= \frac{12\times7}{6} = 14amu$
2. Now there are 2 N atoms for every 1 O atom in the $N_{2}O$. Therefore we need to multiply the m(N) with 2 when calculating the atomic mass of O using the given mass ratio.
$Mr(O)= \frac{Mr(N)\times2\times4}{7}= \frac{14\times2\times4}{7} = 16amu$
$Mr$ represents molecular mass.
