Chemistry Questions and Answers

Answer: A

Biogas is mainly methane.

It is typically 55–65 per cent \(\mathrm{CH_4}\) with most of the rest carbon dioxide, produced when methanogenic bacteria digest cattle dung and other organic waste in the absence of air. The methane is what makes it burn.

Answer: B

Oil of vitriol is sulphuric acid.

The name is alchemical: the acid was first made by distilling green vitriol, hydrated iron(II) sulphate, and its oily viscosity gave it the rest of the name. Aqua fortis is nitric acid and spirit of salt hydrochloric acid.

Answer: B

The atomic number equals the number of protons.

It defines the element and fixes its place in the periodic table. In a neutral atom it also equals the number of electrons, but that equality fails for an ion, whereas the proton count never changes.

Answer: A

PVC stands for polyvinyl chloride.

It is the addition polymer of vinyl chloride, \(\mathrm{CH_2{=}CHCl}\). Rigid PVC is used for pipes and window frames; adding a plasticiser makes it flexible enough for cable insulation and flooring.

Answer: A

Bone does not contain iodine.

The mineral of bone is hydroxyapatite, \(\mathrm{Ca_{10}(PO_4)_6(OH)_2}\), which supplies the calcium, phosphorus and oxygen, and the organic matrix is collagen, which supplies the carbon. Iodine is concentrated in the thyroid gland, where it is built into thyroxine.

Answer: B

John Dalton proposed the first atomic theory, in 1808.

He postulated that matter is made of indivisible atoms, that all atoms of an element are identical in mass, and that compounds form when atoms combine in fixed small whole-number ratios. The theory explained the laws of conservation of mass and of definite and multiple proportions at a stroke.

Answer: B

Antoine Lavoisier is regarded as the father of modern chemistry.

He proved the conservation of mass by careful weighing, showed that combustion is combination with oxygen and so destroyed the phlogiston theory, and introduced the systematic naming of compounds still in use.

Answer: A

Nickel is the catalyst for hydrogenating oils.

Finely divided nickel at about 200 °C with hydrogen at a few atmospheres adds \(\mathrm{H_2}\) across the double bonds of unsaturated vegetable oil, turning the liquid oil into a semi-solid fat. Platinum and palladium do the same but cost far more.

Answer: B

Oxygen is the most abundant element in the earth's crust, at about 46 per cent by mass.

Almost all of it is locked in silicate minerals and oxides rather than free. Silicon follows at 28 per cent and aluminium at 8 per cent, the first metal on the list.

Answer: B

Glycerol is used to make dynamite.

Nitrating glycerol with a mixture of concentrated nitric and sulphuric acids gives nitroglycerine, which is dangerously sensitive to shock as a liquid. Alfred Nobel's contribution in 1867 was to absorb it in kieselguhr, making it safe enough to handle.