Hydroxide of which alkali metal is used in the manufacture of soft soap?

$A$ metal $X$ on heating in a stream of nitrogen gives $Y$. $Y$ on reaction with ${H_2}O$ gives a colorless gas which,when passed through a $CuSO_4$ solution,gives a blue color. What is $Y$?

Identify the correct order of standard enthalpy of formation of sodium halides.

When burnt in excess of oxygen, sodium forms a compound $X$ and potassium forms a compound $Y$. The magnetic natures of $X$ and $Y$ respectively are

Which of the following metal ion plays an important role in muscle contraction?

Which of the following is $CORRECT$ regarding alkali metals?
$I$. Pure $NaCl$ is hygroscopic
$II$. $(n - 1)d$ subshell is vacant only
$III$. Aqueous $NaHCO_3$ solution is more basic than $Na_2CO_3$ solution
$IV$. Both $Li^{+}$ and $Mg^{2+}$ do not form alums