Chemistry Questions and Answers

Answer: B

The correct order is \(\mathrm{Al_2O_3 < MgO < Na_2O < K_2O}\).

Basicity of an oxide increases as the element becomes more metallic - that is, down a group and to the left across a period. \(\mathrm{Al_2O_3}\) is amphoteric, MgO weakly basic, and \(\mathrm{Na_2O}\) and \(\mathrm{K_2O}\) strongly basic, with potassium the most electropositive of the four.

Answer: D

All of these - none of the three is a metal.

Sulphur and nitrogen are non-metallic elements, and sugar is an organic compound, not an element at all. A metal is lustrous, malleable and a good conductor; none of these fits.

Answer: B

\(\mathrm{Na^+}\) has 10 electrons.

A sodium atom has 11 electrons \((2,8,1)\); losing the single 3s electron leaves \(2,8\), the neon configuration. The nucleus still holds 11 protons, which is why the ion is much smaller than the atom.

Answer: A

Nail polish remover contains acetone.

Propanone dissolves the nitrocellulose and resins of the polish quickly and evaporates at once, being volatile. It also strips the natural oils from the nail, which is why acetone-free removers use ethyl acetate instead.

Answer: A

The ozone hole is a thinning of the ozone layer in the stratosphere.

It is not a literal hole but a seasonal depletion, worst over Antarctica in the southern spring, where chlorine radicals released from CFCs destroy ozone catalytically on the surfaces of polar stratospheric clouds. One chlorine atom can destroy many thousands of ozone molecules before it is removed.

Answer: B

The nitride ion has 7 protons and 10 electrons.

Forming \(\mathrm{N^{3-}}\) means gaining three electrons to reach the neon configuration. The number of protons never changes in ion formation - changing it would change the element - so only the electron count moves, from 7 to 10.

Answer: D

Glass has no melting point.

It is an amorphous solid - a supercooled liquid - with no long-range order and therefore no fixed temperature at which the lattice collapses. It simply softens gradually over a range. Crystalline solids such as sodium chloride, and the elements bromine and mercury, all have sharp melting points.

Answer: A

Cineole, also called eucalyptol, gives cardamom oil its flavour.

It makes up a large part of the volatile oil of the seeds, alongside \(\alpha\)-terpinyl acetate. Eugenol is the principal constituent of clove oil, geraniol of rose and citronella oils, and limonene of citrus peel.

Answer: D

Artificially produced radioactive elements belong to the f-block.

Every element beyond uranium is man-made, and neptunium through lawrencium are actinides, which are f-block elements. They are produced by neutron capture in reactors or by bombardment in accelerators.

Answer: A

Iron recovers copper from copper sulphate solution.

\[\mathrm{Fe + CuSO_4 \rightarrow FeSO_4 + Cu}\] Iron is above copper in the reactivity series, so it reduces \(\mathrm{Cu^{2+}}\) to the metal. Silver and mercury lie below copper and cannot; sodium would attack the water first.