Question

The mass spectrum of an unknown compound has a molecular ion peak with a relative intensity of 57.10% and an M+1 peak of 6.83%.

Answer 1

There are 11 Carbon atoms in the compound.

Solution:

Carbon atom count is the ratio of the M peak to the M+1 peak.

$\text{ Number of Carbon atoms }=\frac{\text { Relative intensity of } M+1 \text { peak }}{0.011 \times \text { Relative tntensity of } M \text { peak }}$

Here M peak is 57.10% and M+1 peak is 6.83%. On applying the values in the formula we get,

$\frac{0.0683}{0.011\times0.571g} = 10.87\approx11$

Therefore, the number of Carbon atoms in the compound are 11.

Refer the image attached below for a better understanding of M peak and M+1 peak.

The heaviest ion that has the greatest m/z value is said to be the molecular ion peak in mass spectrum.