Chemical Compounds and Reactions

Copper sulphate is blue in colour because it has been oxidised to the Cu2+ ion which is a d-block metal ion.

This is the correct option. The crystals of copper sulphate are blue in colour due to the water of crystallisation. 

Sodium azide is the inorganic compound with the formula NaN3. This colourless azide salt is the gas-forming component in many car airbag systems. It is used for the preparation of other azide compounds. It is an ionic substance and is highly soluble in water. It is extremely toxic.

Ammonal is an explosive made up of ammonium nitrate, trinitrotoluene (TNT), and aluminium powder. Ammonium nitrate functions as an oxidizer and aluminium as a power enhancer. To some extent,  aluminium makes it more sensitive to detonation. The use of the relatively cheap ammonium nitrate and aluminium makes it a replacement for pure TNT.

Nitrobenzene is a water-insoluble pale yellow oil with an almond-like odour. It freezes to give greenish-yellow crystals. Although occasionally used as a flavouring or perfume additive,. Nitrobenzene is highly toxic in large quantity. 

HHTDD is a powerful but moisture sensitive explosive compound. It is essentially an open analogue of the cyclic nitroamine cage compounds such as CL-20. HHTDD readily decomposes in the presence of even trace amounts of water, making it unsuitable for any practical applications.

Copper(I) oxide or cuprous oxide is the inorganic compound with the formula Cu₂O. It is one of the principal oxides of copper. This red-coloured solid is a component of antifouling paints.

Hydrogen sulfide is a colourless, very poisonous, flammable gas with the characteristic foul odour of rotten eggs at concentrations up to 100 parts per million. It often results from the bacterial breakdown of organic matter in the absence of oxygen, such as in swamps and sewers.

Hydrogen peroxide (H₂O₂) is an oxidizer commonly used as a bleach. It is the simplest peroxide. Hydrogen peroxide is a clear liquid, slightly more viscous than water, that appears colourless in dilute solution. It is used as a disinfectant, antiseptic, oxidizer, and in rocketry as a propellant.

Indium arsenide is a semiconductor material. It has the appearance of grey cubic crystals with a melting point 942 °C. Indium arsenide is used for construction of infrared detectors, for the wavelength range of 1-3.8 µm. The detectors are usually photovoltaic photodiodes.

Germane is the chemical compound with the formula GeH4, and the germanium analogue of methane. It is the simplest germanium hydride and one of the most useful compounds of germanium. It is tetrahedral. It burns in air to produce GeO2 and water.

Diborane is a colourless gas at room temperature with a repulsively sweet odour. Diborane mixes well with air, easily forming explosive mixtures. Diborane will ignite spontaneously in moist air at room temperature.

Diazomethane is the chemical compound CH₂N₂. It is one of the most common diazo compounds. In the pure form at room temperature, it is a famously explosive yellow gas. Diazomethane is always prepared as needed as a solution in ether and used as such.

p-Xylene is an aromatic hydrocarbon, based on benzene with two methyl substituents. It is an isomer of xylene. p-Xylene is used on a large scale for the manufacture of terephthalic acid. Its polymer is known as Parylene.