Question

Give reason for the following

1. Nitric acid in the dilute form is not used in the laboratory preparation of hydrogen from metals.

2. Granulated zinc is preferred to metallic zinc in the preparation of hydrogen using dilute acid.

3. Hydrogen and alkali metals of group [1A] react with copper [II] oxide to give copper.

4. Hydrogen is collected by the downward displacement of water and not even though it is lighter than air.

5. A Mixture of hydrogen and chlorine can be separated by passage through a porous pot

Answer 1

1.Nitric Acid is a very strong oxidising agent. It oxidizes the Dihydrogen Gas produced during the reaction with metals to Water. That is why, Nitric Acid cannot be used for preparation of hydrogen gas.

2.Granulated zinc has a larger surface area than metallic zinc and thus it reacts faster with dilute acids.

3. Alkali metals and hydrogen lie above copper in the activity series. They are more reactive than copper and can displace copper from its compounds.

4. Hydrogen is collected by downward displacement of water as it is less denserthan water. Hence it comes out at the surface of water . It is insoluble in water so it does not dissolve in water. In case of displacement with air, it is not possibleeven if hydrogen is lighter than air (14.5 times lighter than air).

5. A mixture of hydrogen and chlorine can be separated by passage through a porous pot. This is because the diffusibility of hydrogen is more than that of chlorine in the porous pot.

Hydrogen diffuses faster than chlorine into porous pot. Most of the chlorine remains outside the porous pot.