The correct relationships between unit cell edge length '$$a$$' and radius of sphere '$$r$$' for face-centred and body-centred cubic structures respectively are :

Number of water molecules in washing soda and soda ash respectively are :

The reaction used for preparation of soap from fat is :

The correct order for acidity of the following hydroxyl compound is :

A. $$\mathrm{CH}_{3} \mathrm{OH}$$

B. $$\left(\mathrm{CH}_{3}\right)_{3} \mathrm{COH}$$

C.

D.

E.

Choose the correct answer from the options given below: