Test: Chemistry - 1 - UPSC MCQ

Morphine is an analgesic drug that is used to relieve severe pain. It was first isolated in 1804 by Friedrich Serturner, which is generally believed to be the first ever isolation of a natural plant alkaloid in history. Boric acid, also called orthoboric acid, is a weak acid of boron often used as an antiseptic or insecticide. Nickel silver, also known as German silver, is a copper alloy with nickel and often zinc. The usual formulation is 60% copper, 20% nickel and 20% zinc. Sodium is an extremely reactive metal and a powerful reducing agent. When exposed to air, it very quickly oxidizes. It also reacts violently to water. We store sodium under kerosene because kerosene is already highly reduced and won't react with sodium metal.

The electron was discovered in 1896, by the British physicist J. J. Thomson, using cathode rays while doing discharge tube experiments. In 1886, Eugen Goldstein discovered the existence of a new type of rays in discharge tube and named as anode rays or canal rays. Canal or anode rays travel in straight line and are deflected by electric field towards cathode which proves that they are composed of positively charged particles. These lightest positively charged particles were named and characterised as protons by Ernest Rutherford in 1919 who purposed Rutherford model for atom to explain the atomic structure. Anti-electron or in other words the positron was discovered in 1932 by Anderson, a physicists and he found that the bombardment of boron with an alpha particle resulted in the emission of this particle. In 1932, James Chadwick, an English physicist who had worked with Rutherford, detected neutrons.

The “plum pudding model” was put forward by J.J. Thomson in 1904. In this model, the atom is made up of negative electrons that float in a “soup” of positive charge, much like plums in a pudding or raisins in a fruit cake. In 1906, Thomson was awarded the Nobel Prize for his work in this field. Louise de Broglie suggested that electron exhibits a dual nature. Broglie also got Physics Noble Prize for his theory. In 1913, Bohr proposed his quantized shell model of the atom to explain how electrons can have stable orbits around the nucleus. Ernest Rutherford published his atomic theory describing the atom as having a central positive nucleus surrounded by negative orbiting electrons. This model suggested that most of the mass of the atom was contained in the small nucleus, and that the rest of the atom was mostly empty space.

Ultra-violet rays < visible light < infrared radiation < microwaves (0.1 micrometres) (0.7 micrometres ) (0.01 mm) (less than 10 cm)

A nuclear reactor coolant — usually water but sometimes a gas or a liquid metal (like liquid sodium) or molten salt — is circulated past the reactor core to absorb the heat that it generates. The heat is carried away from the reactor and is then used to generate steam. Control rods that are made of a neutron poison are used to absorb neutrons. Absorbing more neutrons in a control rod means that there are fewer neutrons available to cause fission, so pushing the control rod deeper into the reactor will reduce its power output, and extracting the control rod will increase it. A neutron moderator is a medium that reduces the speed of fast neutrons, thereby turning them into thermal neutrons capable of sustaining a nuclear chain reaction involving uranium-235. Commonly used moderators include regular (light) water (roughly 75% of the world's reactors), solid graphite (20% of reactors) and heavy water (5% of reactors). Nuclear fuel is a material that can be 'burned' by nuclear fission or fusion to derive nuclear energy. Nuclear fuel can refer to the fuel itself, or to physical objects (for example, bundles composed of fuel rods) composed of the fuel material, mixed with structural, neutron moderating, or neutron reflecting materials. The most common fissile nuclear fuels are uranium-235 (²³⁵U) and plutonium-239 (²³⁹Pu).

There are two main fundamental differences between the design of an atomic bomb, and the design of a nuclear reactor. One difference is the way the fission reactions are controlled and the second difference stems from the enrichment of the fuel.

Quarks have fractional electric charge values– either 1/2 or 2/3 times the elementary charge. The positron has an electric charge of +1e, a spin of 1/2, and has the same mass as an electron. A neutrino is an electrically neutral, weakly interacting elementary subatomic particle with halfinteger spin. All evidence suggest that neutrinos have mass but that their mass is tiny even by the standards of subatomic particles. Their mass has never been measured accurately.

H₂O has intermolecular hydrogen bond between its molecules (H—O—H------H—O—H) while H₂S has weak Van der Waals forces between its molecules. Hence the molecules of H₂O are strongly packed than H₂S, thus water is at liquid state at room temperature

The rates of most reactions increase with a rise in temperature. Raising the temperature increases the fraction of molecules having very high kinetic energies. These are the ones most likely to react when they collide. The higher the temperature, the larger the fraction of molecules that can provide the activation energy needed for reaction.

Petroleum products are usually grouped into three categories: light distillates (LPG, gasoline, naphtha), middle distillates (kerosene, diesel), heavy distillates and residuum (heavy fuel oil, lubricating oils, wax, asphalt). Hence, the correct option would be: Gasoline, kerosene, diesel.

Except option (2), all are applications of capillary action. One would not be able to consume soft drink, if there is no atmospheric pressure, i.e., in vacuum.

Water molecules scatter blue wavelengths by absorbing the light waves, and then rapidly remitting the light waves in different directions. That is why there are mostly blue wavelengths that are reflected back to our eyes.

Aaron Ciechanover, Avram Hershko and Irwin Rose have been awarded the Nobel Prize in Chemistry 2004 for “...helping to understand how the human body gives the 'kiss of death' to rogue proteins to defend itself from diseases like cancer” (Reuters, 6 October 2004). These scientists—the former two from Israel, the latter from the US — discovered ubiquitin-mediated protein degradation. Knowledge of ubiquitin-mediated protein degradation offers an opportunity to develop drugs against cervical cancer, cystic fibrosis and other diseases.

Thermonuclear fusion, or hydrogen bombs explode with enormous power using uncontrolled self-sustaining chain fusion reactions. Deuterium and tritium, under extremely high temperatures, form helium providing the energy. D + T → ⁴He + n In principle, a mixture of D, T and ⁶Li heated to very high temperature and confined to a high density will start a chain fusion reaction, liberating an enormous amount of energy.

All the three substances are responsible for ozone layer depletion in different ways. Which are: CFC—mostly used in refrigeration, air conditioning and heat pump systems. Halons—used historically as fire suppression agents and fire fighting, but now only allowed in very limited situations. Carbon tetrachloride (tetrachloromethane)—limited solvent used in laboratories and chemical and pharmaceutical industries.

Hydrogen combines with oxygen with explosive force in the presence of a spark.Helium is an inert gas that will not burn or explode, so is much safer to use in balloons instead of hydrogen.

Cerargyrite, also called Horn Silver, gray, very heavy halide mineral composed of silver chloride (AgCl); it is an ore of silver. Tiny particles of silver iodide are sprayed on a cloud from an aeroplane. The particles attract water drops from the cloud. When they form a drop that is large enough, it starts raining. Zinc phosphide is an inorganic compound that is used in pesticide products as a rodenticide.. Zinc oxide is also known as philosopher's wool.

It produces fumes of ammonia and hydrochloric acid.

Hydrofluoric acid is one of the most dangerous acids known. It needs to be treated differently then even strong acids like sulphuric and hydrochloric. HF reacts with many materials, therefore, avoid contact with glass, concrete, metals, water, other acids, oxidizers, reducers, alkalis, combustibles, organics and ceramics.

The zinc serves as a sacrificial anode, so that it cathodically protects exposed steel.