Question

The reaction of an element $A$ with water produces combustible gas $B$ and an aqueous solution of $C$. When another substance $D$ reacts with this solution $C$ also produces the same gas as $B$. $D$ also produces the same gas even on reaction with dilute$H_{2}S{O}_4$ at room temperature. Element $A$ imparts a golden yellow colour to the bunsen flame. Then $A,B,C$ and $D$ may be identified as :

• A. $Na$, $H_2$, $NaOH$ and $Zn$
• B. $K$, $H_2$, $KOH$ and $Zn$
• C. $K$, $H_2$, $NaOH$ and $Zn$
• D. $Ca$, $H_2$, $CaCO{H}_2$ and $Zn$

Answer 1

Answer: (A)

$Na$, $H_2$, $NaOH$ and $Zn$

$2Na+2H_{2}O\to 2NaOH+H_2\left(gas\right)$

Element $A$ would be $Na$ and combustible gas $B$ would be $H_2$ and and an aqueous solution of $C$ would be $NaOH$.
When another substance $D$ reacts with this solution $C$ also produces the same gas as $B$.

$Zn+2NaOH+2H_{2}O\to N{a}_2\left[Zn\right(OH{)}_4]+H_2$
So, $A,B,C$ and $D$ may be identified as $Na$, $H_2$, $NaOH$ and $Zn$.
Hence, option $A$ is correct.