Which one of the following removes temporary hardness of water?

The value of $\cos \frac{2 \pi}{15} \cos \frac{4 \pi}{15} \cos \frac{8 \pi}{15} \cos \frac{14 \pi}{15}$ is :

Acid hydrolysis of $X$ yields two different organic compounds. Which one of the following is $X$?

What is obtained when sodium metal is heated in a stream of dry ammonia?

$A$ solid sphere and a disc of same mass $M$ and radius $R$ are kept such that their curved surfaces are in contact and their centers lie along the same horizontal line. The moment of inertia of the two-body system about an axis passing through their point of contact and perpendicular to the plane of the disc is

What is the molar solubility of $Ag_{2}CO_{3}$ $(K_{sp} = 4 \times 10^{-13})$ in $0.1 \ M \ Na_{2}CO_{3}$ solution?