Select the correct answer from the choice in bracket to complete each sentence:
The gas which has now replaced hydrogen in air balloons is _____________[argon, helium, neon].

Select the correct answer from the choice in bracket to complete each sentence: The product formed on combustion of hydrogen in air is ___________[water gas, water, producer gas].

Select the correct answer from the choice in bracket to complete each sentence: An example of a monoatomic molecule is _______ [hydrogen/helium).

Select the correct answer from the choice in bracket to complete each sentence: The reactive element from the two monoatomic elements is _______ [neon/silicon].

Select the correct answer from the choice in bracket to complete each sentence. Matter is added or removed during a - [chemical/physical] change

Select the correct answer from the choice in bracket to complete each sentence: A foul smelling gas formed when hydrogen reacts with a molten non-metal, is _______[hydrogen chloride, hydrogen sulpide, ammonia].

Select the correct answer from the choice in bracket to complete each sentence: In Bosch process the catalytic reduction of steam to hydrogen is carried out by __________[ CO_(2)CO,C] .

Select the correct answer from the choice in bracket to complete each sentence: A soluble solid is separated from an insoluble solid by ________ [fractional crystallisation/ solvent extraction]

Select the correct answer from the choice in bracket to complete each sentence: Dust in air is an example of________ [heterogeneous/homogeneous) mixture.

Select the correct answer from the choice in bracket to complete each sentence:- An element Z with zero valency is a — [metal/noble gas/non-metal].

Select the correct answer from the choice in bracket to complete each sentence. A change in which a substance retains its identity is a — [physical/chemical] change