General Science GK Questions with Answers – Page 39

Urea, CO(NH₂)₂, contains carbon, oxygen, nitrogen and hydrogen; it has no phosphorus at all and is a nitrogenous fertilizer. Urea carries about 46% nitrogen, the highest of the common solid fertilizers, which is why it is the most widely used fertilizer in India.

X-rays are not used in radar; radar works with microwaves, which have wavelengths of a few centimetres. X-rays lie between ultraviolet rays and gamma rays in the electromagnetic spectrum, with wavelengths from about 10 nm down to 0.01 nm, so about 1 Å (0.1 nm) is typical.

It is an inorganic salt made of the ammonium ion and the cyanate ion, with no carbon–hydrogen bonds. Ammonium cyanate is famous in chemistry because in 1828 Friedrich Wöhler heated it and obtained urea.

Pairs I, II and IV describe the electron transfer correctly; pair III calls bromine a reductant when it is the oxidant.

Boiling an oil or fat with an alkali splits it into glycerol and the salts of its fatty acids; with potassium hydroxide those salts are potassium salts.

Recombinant vector vaccines are made by genetic engineering, and both viruses and bacteria serve as their vectors. In a recombinant vector vaccine, scientists take a harmless or weakened carrier, the vector, and insert into it the gene for an antigen of the disease-causing germ.

Moringa is not a legume and tamarind is not native to South Asia, so statements 1 and 2 are false.

The method uses a natural bacterium to stop mosquitoes from passing on viruses. Wolbachia is a common bacterium that lives inside the cells of many insects.

The Haber process is exothermic, not endothermic: nitrogen and hydrogen combine to form ammonia and release heat. In the Haber process, N2 + 3H2 ⇌ 2NH3 gives out about 92 kJ for every two moles of ammonia formed.

Phloem sieve tubes are not like xylem vessels: sieve tubes are living cells with thin walls and sieve plates, while mature xylem vessels are dead, hollow tubes with thick lignified walls.

The Bohr effect is the fall in haemoglobin's affinity for oxygen when carbon dioxide and acidity rise, so oxygen is unloaded where tissues need it most.

Arteries have the thickest walls of all blood vessels, not the thinnest, because they carry blood away from the heart under high pressure.

Lead nitrate breaks down only when it is heated strongly, so the reaction absorbs heat and is endothermic. On heating, lead nitrate gives lead oxide, brown fumes of nitrogen dioxide and oxygen: 2Pb(NO3)2 → 2PbO + 4NO2 + O2.

A fluid at rest presses on the walls and has pressure at every point, but that pressure is not the same at all depths.

Zero on the Kelvin scale lies 273.15 degrees below the freezing point of water. The Kelvin and Celsius scales have degrees of the same size, so T(K) = t(°C) + 273.15.

Nitrogen and oxygen combine only when a lot of energy is supplied. The nitrogen molecule is held by a very strong triple bond, so breaking it takes much energy, and the reaction N₂ + O₂ → 2NO absorbs heat.

Hydrogen adds across the carbon–carbon double bonds of the oil. Vegetable oils are unsaturated: their fatty acid chains contain C=C double bonds, which keep them liquid.

The charge moves exactly opposite to the field, and a magnetic field exerts no force on a charge moving along its line.

It takes most force to start an object moving, less to keep it sliding and least to keep it rolling.

Urea, CO(NH₂)₂, has a molar mass of 60 g, of which 28 g is nitrogen and 4 g is hydrogen.