The diagram shows the mass spectrum of an alkane, X. What is X likely to be?

A C₁₀H₂₂
B C₆H₁₄
C C₅H₁₂
D C₃H₈

m/e value of molecular ion peak = 72
Therefore the Mr of X is 72.

Choice A: M_r of C₁₀H₂₂ = 10 x 12.0 + 22 x 1.0 = 144

Choice B: M_r of C₆H₁₄ = 6 x 12.0 + 14 x 1.0 = 86

Choice C: M_r of C₅H₁₂ = 5 x 12.0 + 12 x 1.0 = 72

Choice D: M_r of C₃H₈ = 3 x 12.0 + 8 x 1.0 = 44

Therefore, X is C₅H₁₂, Choice C