Question

Lauryl alcohol is obtained from coconut oil and is used to make detergent. A solution of 5 g of Lauryl alcohol in 200 g of benzene freezes at 4°C. The approximate molar mass of Lauryl alcohol will be ______.

Given, K_f of benzene = 5.1°C/molal, Freezing point of benzene = 5.5°C.

[Give your answer after division by 17]

Options

• 2

• 1

• 5

• 9

Answer 1

Lauryl alcohol is obtained from coconut oil and is used to make detergent. A solution of 5 g of Lauryl alcohol in 200 g of benzene freezes at 4°C. The approximate molar mass of Lauryl alcohol will be 5.

Explanation:

`Delta "T"_"f" = "T"_"f"^circ - "T"_"f"`

= 5.5 - 4.0

= 1.5

`Delta "T"_"f" = "K"_"f" xx "m"`

`1.5 = 5.1 xx 5/("M"."wt".) xx 1000/200`

M.Wt. of Lauryl alcohol = `127.5/1.5` = 85 gm

Then divisible by 17  ....(Given)

`therefore 85/17 = 5`