Chemistry MCQs

Notes:
The densest chemical element is Osmium a metal. It has a density of around 22 grams per cubic centimeter, about twice the density of lead.

Notes:
Dolomite is a common rock-forming mineral. It is a calcium magnesium carbonate with a chemical composition of [Ca.Mg(CO3)2. It is the primary component of the sedimentary rock known as dolostone and the metamorphic rock known as dolomitic marble. Dolomite is used in the Pidgeon process for the production of magnesium.

Notes:
Bridgmanite is the accepted name for the mineral silicate perovskite, (Mg,Fe)SiO3, the most common mineral on Earth. It was discovered in Tenham chondrite meteorite, where it associates with another polymorph of MgSiO3 substance – akimotoite.

Notes:
Rusting is a process of slow oxidation of iron by atmospheric oxygen in presence of moisture. It is only oxidation, it is not combustion. Combustion is rapid oxidation by oxygen with the liberation of heat. Rusting is the common term for corrosion of iron. Corrosion is a natural process that converts a refined metals into a more chemically stable form such as oxide, hydroxide etc.

Notes:
Antiperspirants contain antiperspirant actives–usually aluminum salts, which reduce the release of sweat from the sweat glands as they form temporary gel plugs in the most upper parts of the sweat pores. These plugs are removed over time by mechanical action and the natural skin renewal process.

Notes:
Ozone, O3, is a pale blue gas that is unstable and toxic. It is a powerful allotropic of the element oxygen; a high concentration of ozone around the earth absorbs heat.

Notes:
Plaster of Paris is formed from gypsum. The gypsum is heated to 150°Celsius and becomes a dry powder. When this powder is mixed with water it reforms into a paste and eventually hardens into a solid. POP is used in art as a decorative material.

Notes:
Calcium sulfate dehydrate is commonly known as Gypsum.

• It is a soft sulfate mineral composed of with the chemical formula CaSO4•2H2O.
• It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster.
• Asbestos is a term for a group of minerals made of microscopic fibers.
• Limestone is a sedimentary rock composed primarily of calcium carbonate CaCO3, in the form of the mineral calcite.

Notes:
A catalyst is an agent or compound that increases the rate of a reaction without itself being consumed. Enzymes are naturally occurring catalysts responsible for many essential biochemical reactions. Most solid catalysts are metals or the oxides, sulfides, and halides of metallic elements and of the semi-metallic elements boron, aluminum, and silicon.

Notes:
Terylene is a co-polymer of ethylene glycol and terephthalic acid. Also known as Dacron, it is prepared by the condensation polymerization of ethylene glycerol and terephthalic acid with elimination of water. The reaction is carried out at about 420-460 K in the presence of a catalyst consisting of a mixture of zinc acetate and antimony trioxide.