Fill in the blanks: (a) Hydrogen is ............... than air. (b) Hydrogen is ............... soluble in water. (c) Hydrogen burns with a ............... flame and ............... sound is heard. (d) A metal ............... hydrogen in the reactivity series gives hydrogen with ............... . (e) Hydrogen reacts with metal oxides to form ............... and ............... . (f) Oxidation is the removal of ............... or addition of ............... . (g) In redox reactions, oxidation and reduction occurs ............... .

(a) lighter (b) sparingly (c) pale blue, pop (d) above, dilute acids (e) metal, water (f) hydrogen, oxygen (g) simultaneously

Indicate which of the following statements are true and which are false:
(a) Hydrogen molecule is monovalent.
(b) The removal of hydrogen from a substance is called reduction.
(c) Nitric acid cannot be used to prepare hydrogen by its action on active metals.
(d) The reaction between hydrogen and nitrogen to form ammonia is reversible.
(e) Zinc can liberate hydrogen from water, acid and alkali solution.
(f) Hydrogen is combustible as well as a supporter of combustion.
(g) Hydrogen gas is easily liquefiable.