Describe the process of electron impact ionisation of a gaseous sample in a time-of-flight (TOF) mass spectrometer.

Write an equation, including state symbols, to represent the ionisation of a general molecule, symbolised as $X$, in this process.

A volatile organic molecule $Y$ is ionised by electron impact in a TOF mass spectrometer.

• The $Y^{+}$ ion has a kinetic energy of 7.65 × 10^-16 J.
• This ion takes 1.50 × 10^-5 s to reach the detector.
• The length of the flight tube (drift space) is 1.80 m.

Calculate the relative molecular mass ($M_r$) of $Y$.

Use the equations:

$$KE=\frac{1}{2}m{v}^2$$

where $m=mass\; (kg)$ and $v={speed\; (m\; s}^{-1})$.

The Avogadro constant, $L=6.022\times 10^{23}{mol}^{-1}$.