Chemistry MCQs

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MTBE is a gasoline additive, used as an oxygenate to raise the octane number. Its use is controversial in the US and declining in that country in part because of its occurrence in groundwater and legislation favoring ethanol.

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Calamine is an ore that contains zinc carbonate along with impurities like iron oxide. Through smelting, the zinc carbonate in calamine can be reduced to extract pure zinc metal. Other common zinc ores are sphalerite (zinc sulfide) and smithsonite (zinc carbonate). So calamine is considered a zinc ore due to its zinc carbonate content.

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The reaction of alkali metals with water produces Hydrogen gas. These metals are part of the first group on the period table and include lithium, sodium, and potassium. They are known for their vigorous reactions with water, which results in the liberation of hydrogen gas. Along with the gas, this reaction also forms a basic alkali metal hydroxide, which gives the solution its characteristic basic or alkaline properties.

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Hard water is generally found in areas where groundwater is in contact with limestone, chalk and dolomite and gets higher amount of calcium and magnesium dissolved in it.

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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

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Typical composition of the Coal gas is as follows: •Hydrogen 50% •Methane 35% •Carbon monoxide 10% •Ethylene 5%

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The alkaline earth metals have low ionization enthalpies due to fairly large size of the atoms. Since the atomic size increases down the group, their ionization enthalpy decreases.

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Calcium carbonate is used as a building material in the form of marble and in the manufacture of quick lime. Calcium carbonate is also used in the manufacture of high quality paper. It finds its use as an antacid, mild abrasive in tooth paste, a constituent of chewing gum, and a filler in cosmetics.

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Methanol, CH₃OH, also known as ‘wood spirit’. It was produced by destructive distillation of wood.

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The term pewter covers a variety of alloys consisting primarily of tin. It is composed of 85–99% tin, mixed with copper, antimony, bismuth, silver or lead..