A certain mass of a gas was brought from state $A$ to $B$ by following three different paths, namely 1,2 and 3 , respectively. Which of the following relations is correct for the work done?

For the formation of ammonia gas from its constituent elements, the $K_p / K_C$ is

$$ \text { Match the following. } $$

$$ \text { The correct match is } $$

The most effective water softening method is