SABIS Grade 11 - Year 2021/2022 Topic (1) Hydrogen

Properties of Hydrogen Gas

Colorless.
Odorless.
Neutral to Litmus.
Less dense than air.
Insoluble in water.

Reaction of Hydrogen Gas with Air

Reacts with air violently (oxygen) when in contact with a flame.
So it makes a squeaky pop with a lit splint
2H2(g) + O2 --> 2H2O

Isotopes of Hydrogen 

Isotopes are atoms of the same element which have the same number of protons (atomic number) but different number of neutrons (mass number).

Preparation of Hydrogen gas

First : in Laboratory ​

1-Preparing hydrogen from water or steam​

Addition of Very reactive metals (example potassium , Sodium , Lithium , Calcium) + liquid water gives hydrogen gas and metal hydroxide.

or Addition of metals to steam to produce metal oxide and hydrogen gas

2- Preparing Hydrogen from acids​

Addition of moderately reactive metals like magnesium aluminum zinc or iron to dilute hydrochloric acid or sulfuric acid 

Note that less reactive metals can not be used to prepare the hydrogen with dilute acids 
generally metals which are less reactive than hydrogen can not be used

Second : Industrially​

1-Using hydrocarbons​

example by heating a hydrocarbon like methane with steam using a catalyst like nickel , the product is Carbon monoxide and hydrogen gas
The carbon monoxide produced can be reheated with more steam using an iron oxide catalyst to produce Carbon dioxide and hydrogen gas 

2-Using coke​

Coke is a fuel made of coal
The coke is reacted with steam at high temperature (around 1000) degrees celsius to produce carbon monoxide gas and hydrogen gas

    

3-Using Electrolysis​

Electrolysis is the breakdown of a substance using electric current 
the water is broken down by electrolysis into hydrogen and oxygen
Or the NaCl solution (brine) is broken down into chlorine and Hydrogen gases