Important Questions on Practice Paper
Why the Magnesium metal is not preferred for the preparation of hydrogen gas in the laboratory? 
Why the Aluminium metal is not preferred for the preparation of hydrogen gas in the laboratory? Why the Iron metal is not preferred for the preparation of hydrogen gas in the laboratory? Why the lead metal is not preferred for the preparation of hydrogen gas in the laboratory? Name the metal preferred for the preparation of hydrogen gas in the laboratory over Magnesium, Aluminium, Iron and Lead. Name the impurities associated with hydrogen obtained by laboratory method and how are these impurities removed. Give the flame colouration when sodium burns in oxygen. Give the flame colouration when Potassium burns in oxygen. 
