The number of hydrogen atom$(s)$ attached directly to the phosphorus atom in hypophosphorous acid $(H_3PO_2)$ is:

Which of the following is the correct increasing order of enthalpy of vaporization for the given hydrides?

The electronegativity of a group $13$ element '$E$' is the same as that of $Ge$ (on the Pauling scale and up to one decimal point). The $CORRECT$ statements about $E^{3+}$ are:
$A$. It can act as a reducing agent.
$B$. It can act as an oxidizing agent.
$C$. $E^{3+}$ is more stable than $E^+$.
$D$. The standard electrode potential value for $E^{3+}/E$ is positive.

The strongest reducing agent among the following is:

Which of the following statements is correct?

The number of hydroxyl groups in pyrophosphoric acid is ......... .