General Science GK Questions with Answers – Page 29

The law states that for a mixture of gases that do not react, the total pressure is the sum of the partial pressures each gas would exert if it alone occupied the whole volume at the same temperature.

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 kinetic theory of an ideal gas assumes exactly the opposite: that there are no forces of attraction or repulsion between molecules except during the brief moment of a collision.

Temperature is a measure of the average kinetic energy of the particles of a substance, in a solid as in a gas: in a solid the particles are held in fixed positions but vibrate about them, and heating makes the vibrations faster and wider, so the average kinetic energy rises…

The kinetic theory gives the average kinetic energy of a molecule as three halves of the product of the Boltzmann constant and the absolute temperature, and for one mole as three halves of RT.

Graham's law of diffusion states that at the same temperature and pressure the rate at which a gas diffuses is inversely proportional to the square root of its density, and therefore of its molar mass.

Substituting one mole, 273.15 kelvin and one atmosphere in the ideal gas equation gives a volume of 22.4 litres, the molar volume at standard temperature and pressure, and this is the figure used in mole calculations; with the modern standard pressure of one bar the value works out to about…

In SI units the universal gas constant is 8.314 joule per mole per kelvin, obtained by multiplying the Boltzmann constant by the Avogadro number.

Extending the straight line of Charles's law backwards shows that the volume of an ideal gas would become zero at minus 273.15 degrees Celsius, and this point is taken as the zero of the kelvin or absolute scale, at which molecular motion carries its least possible energy.

By Charles's law the volume of a fixed mass of gas at constant pressure is proportional to its absolute temperature, so heating the air inside the envelope makes it expand; some of it escapes from the open mouth, the mass of air left inside falls, its density becomes lower than…

Boyle's law, established in 1662, says that for a fixed mass of gas at constant temperature the product of pressure and volume stays constant, so doubling the pressure halves the volume.

Isobars are atoms of different elements that have the same mass number but different atomic numbers. The mass number is the total of protons and neutrons in the nucleus, so isobars have the same number of nucleons arranged differently: more protons and fewer neutrons in one, the reverse in another.

Heat produced per unit time is the power, and with a fixed battery voltage the power is P = V²/R. So the circuit gives the most heat when its total resistance is the smallest, and the smallest possible resistance comes from joining all three resistors in parallel.

Mature human red blood cells and platelets have no nucleus. Red blood cells lose their nucleus as they mature in the bone marrow; this gives their biconcave disc shape more room for haemoglobin to carry oxygen, but it also means they cannot divide or repair themselves and live only about…

Plant growth regulators, or plant hormones, are small molecules that control growth even in tiny amounts, and each main group comes from a different chemical family.

In dinitrogen pentoxide, nitrogen has an oxidation state of +5, the highest it can reach, because a nitrogen atom has five electrons in its outer shell.

Insulin lets glucose leave the blood and enter body cells, especially muscle and fat cells, and so it lowers the blood sugar level.

The SA node, a small patch of special muscle in the wall of the right atrium, produces the electrical impulse that starts each heartbeat, which is why it is called the pacemaker of the heart.

The equivalent weight of a base is its molecular weight divided by its acidity, which is the number of replaceable hydroxide ions in one molecule.

When iron(III) oxide is heated with aluminium powder, aluminium takes away the oxygen, and the reaction gives out so much heat that the iron produced is molten: Fe2O3 + 2Al → 2Fe + Al2O3 + heat.