Explain:
(a) Ethanol should be rectified after distillation.​

Ethanol (boiling point 78°C) and methanol (boiling point 65°C) are two miscible liquids. There is only a small difference in their boiling points. These two liquids are separated from their mixture by fractional ths distillation.

When vapours of the mixture pass through the fractionating column, repeated liquefaction and vapourisation take place. Subsequently, the vapours of low boiling methanol enter the condenser from the fractionating column, condense to liquid and get collected in the round bottomed flask first. Similarly, ethanol with higher boiling point can be collected later in another round bottomed flask.

the dissociation of nickel hydroxide is follows:

the concentration of hydroxide ion is

the equilibrium constant value of nickel hydroxide is = 6.1 * 10^-^1^6 and thus equilibrium equation can be written as:

thus, concentration of ni is 0.23 * 10^-^4 mol /l