Question

Hydrogen gas is not obtained when zinc reacts with:

• A. Cold water
• B. Hot $NaOH$ solution
• C. $Conc.H_{2}S{O}_4$
• D. Dil. $HCl$

Answer 1

Answer: (A), (C)

The correct options are
A

Cold water

C

$Conc.H_{2}S{O}_4$

Zinc does not react with cold water to produce hydrogen and it produces hydrogen gas by reacting with steam.

When zinc reacts with concentrated sulphuric acid then,

$Zn\left(s\right)+conc.2H_{2}S{O}_4\left(l\right)\to ZnS{O}_4\left(aq\right)+S{O}_2\uparrow +2H_{2}O\left(l\right)$

Instead of hydrogen, zinc reacts with concentrated sulphuric acid to produce zinc sulphate, sulphur dioxide gas and water. Moreover, sulphur dioxide gas has the property to convert lime water milky.