General Science Mixed Quiz: Set 174

A Lewis acid is a species that accepts a pair of electrons, and all three of these can do so.

Bakelite is a phenol-formaldehyde resin, prepared by condensing phenol with formaldehyde; on curing the chains cross-link into a rigid network, giving a hard, heat-resistant and electrically insulating solid used for switches, plug tops, pan handles and distributor caps.

Calcium carbonate, CaCO3, is a compound because calcium, carbon and oxygen are chemically combined in it in a fixed ratio.

Saheli contains centchroman and is a non-steroidal pill taken once a week after an initial daily course, which makes it different from the combined hormonal pills that have to be taken daily and carry hormonal side effects.

Power is the reciprocal of focal length in metres, and 50 cm is 0.5 m, so the power is 1 divided by 0.5, which is +2 dioptre.

A restriction endonuclease recognises a short palindromic sequence in DNA and cuts both strands there, leaving sticky ends that can pair with another piece cut by the same enzyme; Hind II was the first such enzyme to be discovered and EcoRI from Escherichia coli is the most widely used.

A shoot grows upward, away from the pull of gravity, so it is negatively geotropic. A tropism is a directional growth movement of a plant part in response to a stimulus: towards the stimulus is positive, away from it is negative.

Japanese rice plants attacked by this fungus grew abnormally tall and spindly, a condition called the foolish seedling or bakanae disease, and the substance responsible was isolated from the fungus and named gibberellin; gibberellic acid is the best known member of the group.

This statement is wrong because bryophytes, the mosses and liverworts, have no true vascular tissue: they lack xylem to carry water and phloem to carry food.

A star is so far away that it is a point source of light.

This statement is wrong because every photon, whatever its energy, travels in vacuum at the same speed of light, about 3 × 10^8 metres per second.

By bombarding beryllium with alpha particles he obtained a penetrating radiation that could not be bent by electric or magnetic fields, and he showed it to consist of neutral particles of about the mass of a proton, for which he received the Nobel Prize in Physics.

Temporary hardness is caused by the bicarbonates of magnesium and calcium, Mg(HCO3)2 and Ca(HCO3)2. It is called temporary because simple boiling removes it: on heating, the soluble bicarbonates break down into insoluble carbonate or hydroxide, carbon dioxide and water, and the solid settles out.

Ferns and their relatives, such as Selaginella, Lycopodium, Equisetum, Pteris, Adiantum and Marsilea, are the first plants with xylem to conduct water and minerals and phloem to conduct food, and the first with a true root, stem and leaf; for that reason they are also called the vascular cryptogams.

Friction acts along the surfaces in contact, opposite to the direction of motion, not along the line joining the centres of two bodies, so it is non-central.

The Austrian scientist Karl Landsteiner discovered the A, B and O blood groups in 1901 and received the Nobel Prize for Physiology or Medicine in 1930 for the work; he was also associated with the discovery of the Rh factor, named after the rhesus monkey.

The root mean square speed follows from the kinetic gas equation and equals the square root of three RT divided by the molar mass, or equally the square root of three times the Boltzmann constant times the temperature divided by the mass of one molecule.

The correct answer is B, bunchy top of banana, a virus disease in which the plant is severely stunted and its leaves become short, narrow and crowded in a bunch at the top; it is carried by an aphid and by infected suckers used for planting, so control depends on…

In 1887, while studying the sparks produced across a gap between two electrodes, Hertz noticed that the spark passed more easily when ultraviolet light fell on the electrodes, which was the first observation of the photoelectric effect; Hallwachs and Lenard then studied it systematically.

The correct answer is B, Antoine Lavoisier, the French chemist who showed by careful weighing in closed vessels that the total mass of the products of a reaction is exactly equal to the total mass of the reactants, so that matter is neither created nor destroyed in a chemical change.