Chemistry MCQs

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Silver is best conductor of heat while among metals lead is poorest conductor of heat. Cooper and aluminum are good conductor while mercury is a poor conductor.

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Bitumen is a mixture of organic liquids that are highly viscous, black, sticky, soluble in carbon disulfide and composed of highly condensed polycyclic aromatic hydrocarbons.

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Galena and litharge are ores of lead. Galena is the most common ore of lead. It is the natural mineral form of lead (II) sulphid. Litharge is a secondary mineral that forms from the oxidation of galena ores. It is one of the natural mineral forms of Lead(II) oxide.

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The Carbon Group of the periodic table includes the elements carbon, silicon, germanium, tin, lead, and flerovium. These elements have four electrons in the outermost shell. Selenium, however, is not a part of this group. It is a member of the Chalcogens and sits beneath Oxygen in the periodic table. The element number for Selenium is 34. It is known for its photovoltaic and photocatalytic properties.

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The auto-ignition temperature of a liquid, gas or vapor is the temperature at which the substance will ignite without any external heat source. Here is the temperature of some gases: 
Methane -580 °C 
Hydrogen -560 °C 
Propane -493 °C 
Ethylene -425 °C 
Acetylene -305 °C 
Naphtha -290 °C 
Carbon disulfide -102 °C

Notes:
The correct answer is Aryl. In organic chemistry, when a hydrogen atom is removed from a benzene ring (a hydrocarbon), the remaining structure is referred to as an aryl group. Aryl groups are derived from aromatic compounds, specifically those containing a benzene ring. For example, when a hydrogen is removed from toluene (methylbenzene), the resulting aryl group is called a tolyl group. Aryl groups are important in various chemical reactions and are foundational in the synthesis of many organic compounds.

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Vulcanization introduces sulfur cross-links between poly-isoprene chains in natural rubber, restricting movement, which increases stiffness, elasticity, and durability. This chemical modification prevents rubber from becoming sticky or brittle, significantly improving its mechanical properties for industrial and commercial use.

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Plumbism is also known as lead poisoning or  a condition which occurs when there is accumulation of lead in body, usually over a few months' time period and even years.

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The funda is that when a small drop of a strong acid, such as nitric acid, is put onto the metal’s surface, most metals fizz or bubble, whilst precious metals (Gold or Platinum not silver) are unaffected.

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(i) It is an important primary material for manufacturing cement and is the cheapest form of alkali. (ii) It is used in the manufacture of sodium carbonate from caustic soda. (iii) It is employed in the purification of sugar and in the manufacture of dye stuffs.