Chemistry - Study Mode

[#691] Galena is a mineral of
Correct Answer

(C) Lead

Explanation

Solution: Galena, also called lead glance, is the natural mineral form of lead(II) sulphide (PbS). It is the most important ore of lead and an important source of silver. Galena is one of the most abundant and widely distributed sulfide minerals. It crystallizes in the cubic crystal system often showing octahedral forms.

[#692] The iron ore which contains 72% of iron is :
Correct Answer

(A) Magnetite

Explanation

Solution: Magnetite is the best quality of iron ore and contains 72% pure iron. Haematite contains 60% to 70% pure iron ore.

[#693] Bauxite is an alloy of which of the following metals ?
Correct Answer

(A) Aluminium

Explanation

Solution: Bauxite is an alloy of aluminium.

[#694] Hard steel contains
Correct Answer

(B) 0.5 to 1.5 per cent carbon

Explanation

Solution: 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. Carbon steels which can successfully undergo heat-treatment have carbon content in the range of 0.30–1.70% by weight. Trace impurities of various other elements can have a significant effect on the quality of the resulting steel. Trace amounts of sulfur in particular make the steel red-short.

[#695] The purest form of Iron is :
Correct Answer

(D) Wrought iron

Explanation

Solution: Wrought iron is purest form of iron.