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 …………… .

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.

Give reasons for the following:

(a) Hydrogen can be used as a fuel.

(b) Though hydrogen is lighter than air it cannot be collected by downward displacement of air.

(c) A pop sound is produced when hydrogen gas is burnt.

(d) Helium has replaced hydrogen in weather observation balloons.

(e) Nitric acid is not used for the preparation of hydrogen gas.

Name the following:

(a) Two metals which give hydrogen with cold water.

(b) A metal which liberates hydrogen only when steam is passed over red hot metal.

(c) The process in which oxygen is added or hydrogen is removed.

(d) A metallic oxide which can be reduced into metal by hydrogen.