Question

If glycerol and methanol were sold at the same price in the market, which would be cheaper for preparing an antifreeze solution for the radiator of an automobile?

• A. Glycerol
• B. Methanol
• C. Both are equal
• D. None of these

Answer 1

The correct option is B Methanol

Antifreeze, any substance that lowers the freezing point of water. It is used in automobile cooling system to prevent radiators from any damage.

Glycerol and methanol both are solute and we know that

$\Delta T_f=K_f\ast m$ = $\frac{molesofsolute}{massofsolvent}$

so, lower the molar mass of solute more will be the depression in freezing point and methanol (32 g/mol) is having lower mass than glycerol (91 g/mol)

Since glycerol has a molecular mass of 91.1 g/mol91.1 g/mol, 1 kg will contain 11.0 moles of solute. Methanol has a molecular mass of 32.0 g/mol32.0 g/mol, so 1 kg will contain 31.2 moles of solute.

So, for any given price per kg, methanol will give you 31.2/11.0=2.931.2/11.0=2.9 times as many moles of solute, resulting in a 2.9 times greater freezing point depression. Hence, methanol is cheaper than glycerol.