Chemistry MCQs

Notes:
Number of Protons will be 17 (atomic number) and neutrons will be 37-17=20.

Notes:
Antoine Lavoisier was a French nobleman and chemist who was central to the 18th-century chemical revolution and who had a large influence on both the history of chemistry and the history of biology. He is widely considered in popular literature as the “father of modern chemistry”. Lavoisier is most noted for his discovery of the role oxygen plays in combustion. He recognized and named oxygen and hydrogen.

Notes:
The nucleus is the very dense region consisting of
protons and neutrons at the center of an atom. It was
discovered in 1911, as a result of Ernest Rutherford’s interpretation of the famous 1909 Rutherford experiment performed by Hans Geiger and Ernest Marsden, under the direction of Rutherford. The proton–neutron model of nucleus was proposed by Dmitry Ivanenko in 1932. Almost all of the mass of an atom is located in the nucleus, with a very small
contribution from the orbiting electrons.

Notes:
The fundamental reason for the bonding of atoms is that they lose their stored potential energy by forming bonds. This is the only reason for chemical combination. So, when a bond is formed between two atoms, stored potential energy is always released to the surroundings. However, the total energy of the system involving reaction remains constant.

Notes:
A colloidal solution, occasionally identified as a colloidal suspension, is a mixture in which the substances are regularly suspended in a fluid. Though colloidal systems can occur in any of the three key states of matter gas, liquid or solid, a colloidal solution unambiguously refers to a liquid concoction. Cheese is an example of colloidal solution of liquid in solution.

Notes:
The law of definite proportion, sometimes called Proust’s law, states that a given chemical compound always contains its component elements in fixed ratio (by mass) and does not depend on its source and method of preparation. For example, oxygen makes up about 8/9 of the mass of any sample of pure water, while hydrogen makes up the remaining 1/9 of the mass.

Notes:
The term hardened steel is often used for a medium or high carbon steel that has been given the heat treatments of quenching followed by tempering. The quenching results in the formation of metastable martensite, the fraction of which is reduced to the desired amount during tempering. This is the most common state for finished articles such as tools and machine parts. In contrast, the same steel composition in annealed state will be softer as required for forming and machining.

Notes:
Concentrated nitric acid is a very strong oxidator capable of reacting with the noble metals such as copper or silver. Some precious metals, such as pure gold and platinum-group metals do not react with nitric acid. However, pure gold does react with aqua regia, a mixture of concentrated nitric acid and hydrochloric acid.

Notes:
Iron is extracted from iron ore in a huge container called a blast furnace. Iron ores such as hematite contain iron oxide. The oxygen must be removed from the iron oxide to leave the iron behind. Reactions in which oxygen is removed are called reduction reactions. Both carbon and carbon monoxide are used in the reduction of the iron oxide (Fe2O3) to give iron.

• 2Fe2O3 + 3C —> 4Fe + 3CO2
• CO2 + C —> 2CO.
• Fe2O3 + 3CO —> 2Fe + 3CO2

Notes:
Sodium sulfate decahydrate (Na₂SO₄·10H₂O) is called Glauber’s Salt. Johann Rudolf Glauber discovered this compound in the 17th century. It is an inorganic salt and crystallizes with ten molecules of water. Glauber’s Salt forms colorless, transparent monoclinic crystals at room temperature. It is widely used in the paper and glass industries as well as in detergents.