Question

When a metal $X$ is treated with cold water, it gives a basic salt $Y$ with molecular formula $XOH$ (molecular mass $=40$) and liberates a gas $Z$ which easily catches fire. Identify $X,Y$ and $Z$.

• A. $Y$ is $NaOH$, $Z$ is $H_2$
• B. $Y$ is $NaOH$, $Z$ is $C{O}_2$
• C. $Y$ is $KOH$, $Z$ is $H_2$
• D. $Y$ is $KOH$, $Z$ is $C{O}_2$

Answer 1

Answer: (A)

The salt is $NaOH$ and its molar mass can be calculated as follows:

$Na\left(23\right)+O\left(16\right)+H\left(1\right)=23+16+1=40$

It is clear that X is sodium, Y is sodium hydroxide and Z is hydrogen. The reaction can be shown by following equation: $2Na+2H_{2}O\to 2NaOH+H_2+\text{Heat}$

Hydrogen is a highly inflammable gas and hence it easily catches fire.