Test: Chemistry - UPSC MCQ

2017-Indian Express

The Ministry of Agriculture has issued a notification inviting objections and suggestions from the stakeholders on completely banning pesticides/ insecticides  including Benomyl, Carbaryl, Diazinon, Fenarimol, Fenthion, Linuron, MEMC, Methyl Parathion, Sodium Cyanide, Thiometon, Tridemorph, Trifluralin, Alachlor, Dichlorvos, Phorate, Phosphamidon, Triazophos and Trichlorfon. So, A is the right answer.

Pyrolysis is a process of combustion in absence of oxygen or the material burnt under controlled atmosphere of oxygen. It is an alternative to incineration. The gas and liquid  thus obtained can be used as fuels.

Monosodium Glutamate (MSG) is a flavor enhancer in Chinese food, but leads to obesity and liver inflation. This was in news because of Maggie noodles controversy. So, 3 is right.

• Brominated vegetable oils are used as stabilizers in the baked goods, soft drinks, soups, jellies etc. but banned in UK after 1970. so, #2 is right.

There is only one combination where 1 and 3 are together i.e. answer "D": 1, 2 and 3 are correct.

Fly ash brick (FAB) is a building material, specifically masonry units, containing class C fly ash and water. All fly ash includes substantial amounts of silicon dioxide (SiO₂) aluminum oxide (Al₂O₃) and calcium oxide (CaO), the main mineral compounds in coal-bearing rock strata. Fly ash can be used as a replacement for some of the Portland cement contents of concrete.

Brominated flame retardants used in many household products are highly resistant to degradation in the environment and they are able to accumulate in humans and animals.

Shell gas contains methane, according to first statement, it contains propane and butane which is wrong. The source of  shell gas is available in India. So the statement (2) is also wrong.

Chemical changes occur when a substance combines with another to form a new substance. Crystallization of sodium chloride is not a chemical as water of crystallization can be lost to get salt again. Similarly melting of ice is reversible. However souring of milk is a chemical change as it is not reversible and a new compound is formed.

Acid rain is caused by a chemical reaction that begins when compounds of sulphur dioxide and nitrogen oxide react with molecules in the atmosphere to produce acids.

Bagasse is often used as a primary fuel source as it produces sufficient heat energy. Molasses can be used for the production of Ethanol. Ethanol is produced by the age old technique of fermentation of cereals, grams, molasses and other materials with high starch contents. Molasses is an inexpensive and readily available raw material.
Molasses cannot be used as a synthetic fertilizer as molasses contain calcium, magnesium and Iron where as synthetic fertilizers are comprised of NPK i.e. Nitrogen, Phosphorous and Potassium.

The burning of fossil fuel can create an other atmospheric pollution problem known as Photochemical Smog. Photochemical smog is a condition that develops when primary pollutants like oxides of nitrogen, Volatile organic compounds created from fossil fuel combustion interact under the influence of sunlight to produce secondary pollutants. The major chemical pollutants in Photochemical smog are NO and NO₂, VOCs(volatile organic compounds), Ozone(O₃) and PAN (Peroxyacetyl Nitrate). NO₂ decreases visibility due to yellowish colour. It also contributes to heart and lung problem. Ozone(O₃) contributes to bronchial constriction, coughing and wheezing. PAN causes eye irritation, high toxicity to plants.

Chlorofluorocarbons are used in the production of plastic foams, in cleaning electronic components and as pressurizing agents in aerosol cans.

Smelting units and paints are the source of the lead poisoning.

Ultraviolet radiation inactivates / kills harmful micro organisms in water only.

By products of power thermal plant operation need to be considered in both the design and operation. Waste heat due to the finite efficiency of the power cycle must be released to the atmosphere, using a cooling tower, or river or lake water as a cooling medium. The gas from combustion of the fossil fuels is discharged to the air; this contains carbon dioxide and water vapour, as well as other substances such as nitrogen, nitrogen oxides, sulphur oxides, and (in the case of coal-fired plants) fly ash, mercury and traces of other metals.

Heavy water (H₂O) and solid graphite is generally used to slow down the speed of neutrons.