Question

When a substance $A$ reacts with water, it produces a combustible gas $B$ and a solution of substance $C$ in water. $D$ reacts with this solution of $C$ and produces the same gas $B$ on warming. $D$ can also produce gas $B$ on reaction with dilute $H_{2}S{O}_4$. $A$ imparts a deep golden yellow colour to a smokeless flame. $A,B,C$ and $D$ are respectively:

• A. $Na,H_2,NaOH,Zn$
• B. $K,H_2,KOH,Al$
• C. $Ca,H_2,Ca(OH{)}_2,Sn$
• D. $Ca{C}_2,C_2{H}_2,Ca(OH{)}_2,Fe$

Answer 1

The correct option is A $Na,H_2,NaOH,Zn$

$A$ imparts a deep golden yellow colour to a smokeless flame. This indicates $A$ is $Na$.

Sodium $\left(A\right)$ reacts with water, it produces a combustible gas hydrogen $\left(B\right)$ and a solution of substance $C$ $\left(NaOH\right)$ in water.

The reaction is as follows:

$2Na+2H_{2}O\to 2NaOH+H_2$

Zinc $\left(D\right)$ reacts with this solution of $C\left(NaOH\right)$ and produces the same gas $B$ (hydrogen) on warming.

$Zn+2NaOH\to \underset{\left(\text{sodium zincate}\right)}{N{a}_{2}Zn{O}_2}+H_2$

$D$ can also produce gas $B$ on reaction with dilute $H_{2}S{O}_4$.

$Zn+H_{2}S{O}_4\to ZnS{O}_4+H_2$

Thus, $A,B,C$ and $D$ are $Na,H_2,NaOH$ and $Zn$ respectively.

Hence, the correct option is $\text{A}$