Hydrogen

Question 1

How can you obtain hydrogen using a reactive metal?

Answer 1

Some H2SO4 is poured by means of the dropping funnel onto the zinc dust and effervescence, indicating liberation of hydrogen. Write the equation.

Question 2

Other acids and metals can be used to obtain hydrogen. Mention two.

Answer 2

Reaction of Magnesium with HCL and reaction of iron with HCL. Write the equation.

Question 3

What do I need to add to require dry hydrogen when i use magnesium and iron with HCL?

Answer 3

Pass it through anhydrous calcium chloride in a U-Tube or concentrated sulphuric acid in a wash bottle (upward delivery)

Question 4

How can i obtain hydrogen with a reaction of metal with water?

Answer 4

The metals are potassium, sodium, calcium. (write the equations)

Question 5

How can i obtain hydrogen by the reaction of metals with steam? Write the equations.

Answer 5

The metals are Mg, Zn and Fe.

Question 6

How can i obtain hydrogen by the reaction of amphoteric metals with caustic alkalis?

Answer 6

Amphoteric metals such as Al and Zn react with sodium hydroxide or potassium hydroxide to obtain hydrogen.

Question 7

What are amphoteric metals?

Answer 7

They are metals that react both with acids and base.

Question 8

What are caustic alkalis?

Answer 8

They are strong corrosive alkali like hydroxide

Question 9

How can you acquire hydrogen by electrolysis?

Answer 9

By dilute acids and dilute alkalis such as sulphuric acid, which gives hydrogen at the cathode and oxygen at the anode.

Question 10

How can i obtain hydrogen from methane? (industrial)

Answer 10

If methane is heated, in the absence of air, to a high temperature (1000°C) in the presence of a catalyst, e.g. aluminium oxide, the gas breaks down into carbon and hydrogen. The process is known as cracking.
CH4 (g) → C (s) + 2H2 (g)

Question 11

What is methane?

Answer 11

Methane is a colourless, odourless flammable gas and is a member of hydrocarbons.

Question 12

How can i obtain hydrogen mixed with steam? (industrial)

Answer 12

A mixture of natural gas (methane) and steam is passed over a
nickel catalyst. The process occurs in a number of stages but the overall reaction is mainly:
CH4 (g) + H2O (g) → CO (g) + 3H2(g)
The carbon monoxide is converted to carbon dioxide
The carbon dioxide is removed by dissolving it in water under pressure to leave hydrogen.

Question 13

Describe the bosch process.

Answer 13

1. Pass steam over red hot coke. C(s) + H2O (g) → CO (g) + H2 (g)
2. The bosch process involves passing H2O (g) over iron(3) oxide catalyst. CO is converted to CO2.
3. CO2 is removed by dissolving it under pressure.

Question 14

Hydrogen is also obtained as a by product in the electrolysis of ….. (industrial)

Answer 14

brine (sodium chloride solution)

Question 15

Name 6 physical properties of hydrogen.

Answer 15

odourless gas
colourless
less dense than air
neutral
diffuses very rapidly.
slightly soluble in water.

Question 16

Test for hydrogen in a lab

Answer 16

a burning splint is put near hydrogen and it burns with a pop sound.

Question 17

Combustion of hydrogen in air to form water

Answer 17

Pure hydrogen burns steadily and quietly in air with a pale blue flame.
the product of combustion of hydrogen is water.
H2 (g) + O2 (g) → H2O (l)
The reaction is very exothermic (heat is liberated) so hydrogen is a very good fuel.

Question 18

Advantages of hydrogen as a fuel

Answer 18

Harmless to environment
very light
can be obtained via unpolluting sources ex: electrolysis of water
does not occupy a lot of space

Question 19

disadvantages of hydrogen as a fuel

Answer 19

difficult to produce
difficult to store
difficult to transport

Question 20

Chemical reaction involving hydrogen

Answer 20

1. Reaction of hydrogen with metals (groups 1 and 2)
2. Reaction of hydrogen with non- metals ( with halogens and with nitrogen). Note :
   When it reacts with nitrogen it forms ammonia.
3. Hydrogen as a reducing agent. (it removes oxygen from oxides of metals ex: CuO
   e.g. CuO (s) + H2(g) → Cu (s) + 2H2O (g)
   Copper oxide is reduced to copper, by loss of oxygen. Hydrogen itself is oxidised to water
   by gain of oxygen.

Question 21

Uses of hydrogen

Answer 21

Fuel
manufacture of margarine, ammonia, HCL
cutting of steel