Practice MCQ Questions and answers on Chemistry-GK

Brass is a homogeneous mixture (solid solution) of copper and zinc.

Bridgmanite is earth's most abundant mineral.

Bronze is an alloy traditionally composed of copper and tin.

Steel is an alloy made by combining iron and other elements, the most common of these being carbon. When carbon is used, its content in the steel is between 0.2% and 2.1% by weight, depending on the grade. Other alloying elements sometimes used are manganese, chromium, vanadium and tungsten. Carbon and other elements act as a hardening agent, preventing dislocations in the iron atom crystal lattice from sliding past one another. Varying the amount of alloying elements and the form of their presence in the steel (solute elements, precipitated phase) controls qualities such as the hardness, ductility, and tensile strength of the resulting steel. Steel with increased carbon content can be made harder and stronger than iron, but such steel is also less ductile than iron. Alloys with a higher than 2.1% carbon content are known as cast iron because of their lower melting point and good castability.

Copper is refined by roasting.

Froth floatation process to concentrate the minerals is applicable to Chalcopyrites.

Epsom salt is used as purgative.

Aluminium ore is called bauxite . The bauxite is purified to produce aluminium oxide, a white powder from which aluminium can be extracted.

Hematite, also spelled haematite, heavy and relatively hard oxide mineral, ferric oxide (Fe₂O₃), that constitutes the most important iron ore because of its high iron content (70 percent) and its abundance. Its name is derived from the Greek word for “blood,” in allusion to its red colour. Many of the various forms of hematite have separate names. The steel-gray crystals and coarse-grained varieties have a brilliant metallic lustre and are known as specular iron ore; thin scaly types are called micaceous hematite. Much hematite occurs in a soft, fine-grained, earthy form called red ochre or ruddle. Intermediate between these types are compact varieties, often with a reniform surface (kidney ore) or a fibrous structure (pencil ore). Red ochre is used as a paint pigment; a purified form, rouge, is used to polish plate glass. The most important deposits of hematite are sedimentary in origin. The world’s largest production (nearly 75 million tons of hematite annually) comes from a sedimentary deposit in the Lake Superior district in North America.