Chemistry MCQs

Notes:
The most important form of elemental phosphorus from the perspective of applications and chemical literature is white phosphorus. It consists of tetrahedral P4 molecules, in which each atom is bound to the other three atoms by a single bond. This P4 tetrahedron is also present in liquid and gaseous phosphorus up to the temperature of 800 °C when it starts decomposing to P2 molecules

Notes:
Polyvinyl chloride (PVC) is made from the monomer vinyl chloride (CH2 =CHCl). It is used for making raincoats, handbags, toys including dolls, electrical goods and as a covering of electrical wires.

Notes:
Graphite is renowned for its conspicuous uses owing to its unique properties like its ability to conduct electricity, which makes it ideal for electrode manufacturing. It’s also used as a lubricant and in the production of crucibles, thanks to its high melting point. However, it isn’t used in glass cutting.

Notes:
Froth and foams are examples of “gas suspended in liquid”. They are typically created when gas bubbles are dispersed in a liquid. This physical phenomenon is commonly observed in many daily life scenarios such as soap lather and carbonated drinks. Technically, they are a special case of colloid where little blobs of one liquid are dispersed in another and show the property of surface tension.

Notes:
The correct answer is Octaoxygen. Octaoxygen (O8) is an allotrope of oxygen that can exist in multiple phases under varying pressures and temperatures. It was first synthesized in 2001 and is notable for its unique molecular structure, which consists of eight oxygen atoms. Ozone (O3) is well-known but does not exhibit multiple phases like octaoxygen. Tetraoxygen (O4) is less stable and not commonly referenced in the same context.

Notes:
Pyrolusite, Braunite, Psilomelane, and Rhodochrosite are all ores of Manganese. Pyrolusite is one of the most important ores due to its high manganese content. Braunite, although a significant ore, its manganese content is less than Pyrolusite. Psilomelane and Rhodochrosite also contribute as minor ores.

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All members of group 14 are solids. Carbon and silicon are non-metals, germanium is a metalloid, whereas tin and lead are soft metals. Melting points and boiling points of group 14 elements are much higher than those of corresponding elements of group 13.

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Carnalite is an ore of Potassium. It’s a hydrated potassium magnesium chloride. The chemical formula of Carnalite is KCl. MgCl₂ . 6H₂O.

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Zone refining works on the principle that impurities are more soluble in the melt than in the solid state of the metal. This method is very useful for producing semiconductors.

Notes:
Zeeman effect refers to the splitting of a spectrum line into several components by the application of a magnetic field. It is named after the Dutch physicist Pieter Zeeman.