Which one of the following removes temporary hardness of water?

Which phylum is characterized by the presence of a central cavity known as the spongocoel?

For the reaction $N_{2(g)} + O_{2(g)} \rightleftharpoons 2NO_{(g)}$,the equilibrium constant $(K_c)$ at temperature $T$ is $4 \times 10^{-4}$. What is the value of $K_c$ for the reaction $NO_{(g)} \rightleftharpoons 1/2 N_{2(g)} + 1/2 O_{2(g)}$ at the same temperature?

The phenomenon of 'industrial melanism' demonstrates:

$A$ solid has a structure in which $W$ atoms are located at the corners of a cubic lattice,$O$ atoms at the centre of edges,and $Na$ atoms at the centre of the cube. The formula for the compound is

$ f: R \rightarrow R $ and $ g:[0, \infty) \rightarrow R $ are defined by $ f(x)=x^{2} $ and $ g(x)=\sqrt{x} $. Which one of the following is not true?