Chemistry MCQs

Notes:
Sublimation is the transition of a substance directly from the solid to the gas phase, without passing through the intermediate liquid phase.

Notes:
• Bronze is an alloy consisting primarily of copper, commonly with about 12–12.5% tin and often with the addition of other metals (such as aluminium, manganese, nickel or zinc) and sometimes non-metals or metalloids such as arsenic, phosphorus or silicon.
• Brass is an alloy of copper and zinc, in proportions which can be varied to achieve varying mechanical and electrical properties.
• Steel, alloy of iron and carbon in which the carbon content ranges up to 2 percent (with a higher carbon content, the material is defined as cast iron).
• Zinc is a chemical element with the symbol Zn and atomic number 30. Zinc is a slightly brittle metal at room temperature and has a blue-silvery appearance.

Notes:
The reason that it is paramagnetic is because the oxygen molecule has two unpaired electrons. Electrons not only go around the atom in their orbitals, they also spin, which creates a magnetic field. Unpaired electrons spin in the same direction as each other, which increases the magnetic field effect.

Notes:
Aufbau principle states that ‘in the ground state of the atom, the orbitals are filled in order of their increasing energies, starting with the orbital of lowest energy.’ The word aufbau is German word which means building up. The increasing order of energy and hence that of filling of orbitals is as follows: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p.

Notes:
In 1828, Friedrich Wöhler synthesized urea, thereby establishing that organic compounds could be produced from inorganic starting materials, disproving the theory of vitalism. Later in 1847, Hermann Kolbe obtained acetic acid from completely inorganic sources, further disproving vitalism.

Notes:
Tap water contains ions (due to dissolved impurities) which help in conduction of electricity. Whereas, distilled water does not contain ions, so it can not conduct electricity.

Notes:
Despite its name, German Silver, developed in the early 18th century as a less expensive substitute for silver, contains no actual silver. It is also known as Nickel Silver and is composed primarily of copper, zinc, and nickel. Copper ranges between 50% and 61.6%, zinc 17.2% and 19%, and nickel between 21.1% and 30%. Occasionally traces of tin and lead are present. The metal’s hardness, toughness, and corrosion resistance make it popular for tableware, marine fittings, and heating coils. Its high electrical resistance allows for its use in heating elements.

Notes:
During nuclear fission, a neutron collides with a uranium nucleus and splits it into lighter nuclei, releasing energy and more neutrons. These released neutrons then can strike other uranium nuclei, causing more fission reactions and propagating the chain reaction.

Notes:
Sublimation describes a phase transition where a substance changes from a solid directly to a gas, bypassing the liquid state. This physical transformation is distinct from chemical changes like oxidation or reduction. Sublimation happens under certain combinations of pressure and temperature. Examples include dry ice (solid CO2), which sublimates at room temperature, and solid water, or ice, which sublimates under low pressure conditions.

Notes:
J. J. Thomson discovered a negatively charged particle, called the electron. The alpha particle is nothing but positively charged helium nuclei, it has charge of two time of that of the proton, as it is constituted of two protons.