1.0 mole of ethyl alcohol and 1.0 mole of acetic acid are mixed. At equilibrium, 0.666 mole of ester is formed. The value of equilibrium constant is

1 mole of C₂H₅OH react with 1 mole of CH₃COOH gives 1 mole of CH₃COOC₂H₅ and 1 mole of H₂O

'X₁' mole of C₂H₅OH react with 'X₂' mole of CH₃COOH gives 0.666 mole of COOC₂H₅ and X₃ moles of H₂O

X₁ = X₂ = X₃ = 0.666

Stoichiometry
Initial moles	1	1		0	0
Moles at equilibrium	(1 - 0.666)	(1 - 0.666)		0.666	0.666