Methanol and ethanol are liquids of similar nature, but a mixture of them is a non-ideal solution. Why?

Explanation

Both methanol and ethanol are individually associate liquids, due to intermolecular hydrogen bonding. Upon mixing these alcohols, a homogeneous solution is formed. In the solution also intermolecular hydrogen bonds are present, but compared to those present in the components is less. Hence, the mixture shows positive deviation from Raoult.s law.