Chemistry - Study Mode
[#301] Which variety of coal contains recognisable traces of the original plant material ?
Correct Answer
(C) Peat
Explanation
Solution: Peat contains recognizable traces of the original plant material. Initially the peat is converted into lignite or ‘brown coal’ - these are coal-types with low organic maturity. In comparison to other coals, lignite is quite soft and its colour can range from dark black to various shades of brown.
[#302] Which of the following processes is used for the production of Biodiesel ?
Correct Answer
(C) Transesterification
Explanation
Solution: Biodiesel production is the process of producing the biofuel, biodiesel, through the chemical reactions of transesterification and esterification. This involves vegetable or animal fats and oils being reacted with short-chain alcohols (typically methanol or ethanol).
[#303] The chief source of naphthalene is
Correct Answer
(A) Coal-tar
Explanation
Solution: Most naphthalene is derived from coal tar. From the 1960s until the 1990s, significant amounts of naphthalene were also produced from heavy petroleum fractions during petroleum refining, but today petroleum-derived naphthalene represents only a minor component of naphthalene production.
[#304] The gas that usually causes explosions in coal mines is
Correct Answer
(D) Methane
Explanation
Solution: There are two main types of coalmine explosions: methane and coal dust. Methane explosions occur when a buildup of methane gas contacts a heat source and there is not enough air to dilute the gas level below its explosion point.
[#305] Submarines move under water. They have engines that run on
Correct Answer
(B) Diesel
Explanation
Solution: Early submarines used a direct mechanical connection between the engine and propeller, switching between diesel engines for surface running, and electric motors for submerged propulsion. Diesel electric submarines have a stealth advantage over their nuclear counterparts.