Question

Which of the following metals will give $H_2$ on reaction with aqueous $NaOH$:
$I:Zn$ $II:Mg$
$III:Al$ $IV:Be$

• A. $I,II,III,IV$
• B. $I,III,IV$
• C. $II,IV$
• D. $I,III$

Answer 1

The correct option is B $I,III,IV$

Among the alkaline earth metals, only $Be$ gives $H_2$ gas on reaction with $NaOH$ as it is amphoteric in nature. Other alkaline earth metals don't react with $NaOH$ as down the group basicity increases. The corresponding reaction is:
$Be+2NaOH+2H_{2}O\to N{a}_2\left[Be\right(OH{)}_4]+H_2$
Similarly aluminium also reacts with $NaOH$ liberating hydrogen gas and forming aluminates. The corresponding reaction is:
$2Al+2NaOH+6H_{2}O\to 2NaAl(OH{)}_4+3H_2$
Again $Zn$ also shows amphoteric nature. On reaction with $NaOH$ it also forms zincates similar to aluminates. The corresponding reaction is:
$Zn+2NaOH+2H_{2}O\to N{a}_{2}Zn(OH{)}_4+H_2$