Which of the following alkali metals has a density greater than water?

$X$ $\xrightarrow{N_2, \Delta} Y$ $\xrightarrow{H_2O} Z$ (colourless gas) $\xrightarrow{CuSO_4} T$ (blue colour)
Then,substances $Y$ and $T$ are

The carbonate which does not leave a residue on heating is

The total number of elements among $S$,$P$,$Zn$,$Al$,$Sn$,$Pb$ which produce $H_2$ gas with $NaOH$ is

The correct order of solubility for the given compounds is:

Compound $A$ reacts with $NH_4Cl$ and forms a compound $B$. Compound $B$ reacts with $H_2O$ and excess of $CO_2$ to form compound $C$,which on reaction with saturated $NaCl$ solution forms sodium hydrogen carbonate. Compounds $A, B$ and $C$ are respectively: