Răspuns :
CH3-CH2-CH2-CH2-CH2-CH3 → CH4 + CH2=CH-CH2-CH2-CH3
CH3-CH2-CH2-CH2-CH2-CH3 → CH3–CH3 + CH2=CH-CH2- CH3
CH3-CH2-CH2-CH2-CH2-CH3 → CH3–CH2-CH3 + CH2=CH- CH3
CH3-CH2-CH2-CH2-CH2-CH3 → CH3–CH2- CH2-CH3 + CH2=CH2
Se considera 100 L amestec final.
In 100 L amestec final sunt 20L etena si 20 L butan, restul de 60L fiind metan, pentena, etan, butena, propan, propena.
Se observa ca 100 L amestec de gaze se obtine din 50 L butan supus cracarii. Din 50L butan introdus 20 L se transforma in etena
η=volumul transformat∙100/volumul introdus = 20∙100/50 = 40%