130. Which of these medicines is NOT used to neutralise or suppress excess stomach acid?
[JEE Main Offline Chemistry — 2015]
(A) Cimetidine
(B) Ranitidine
(C) Phenelzine
(D) Aluminium hydroxide
Answer: (C) Phenelzine
Explanation: Phenelzine is a monoamine oxidase inhibitor prescribed for certain psychiatric disorders, not an acid-suppression medicine. Aluminium hydroxide neutralises gastric acid directly, while cimetidine and ranitidine reduce gastric acid secretion by blocking H₂ histamine receptors.
129. Which one of the following is not considered an explosive material in the given list?
[UPPSC Civil Service Prelims — 2014, Paper 1]
(A) Trinitrotoluene
(B) Dinitroglycerine
(C) Cyclotrimethylenetrinitramine
(D) Nitrochloroform
Answer: (D) Nitrochloroform
Explanation: The published examination key identifies nitrochloroform, also called chloropicrin, as the odd one out. It is chiefly known as a toxic fumigant rather than a conventional blasting explosive. The other options are associated with energetic nitrate or nitro compounds.
128. About coalbed methane and shale gas:
1. Shale gas contains only propane and butane.
2. India has no shale gas sources.
Which statements are correct?
[UPSC CSE Prelims — 24 Aug 2014]
(A) 1 only
(B) 2 only
(C) Both 1 and 2
(D) Neither 1 nor 2
Answer: (D) Neither 1 nor 2
Explanation: Coalbed methane and shale gas are unconventional sources of natural gas dominated by methane rather than solely propane and butane. Shale formations in India have been assessed for hydrocarbon potential, so the claim that no such sources exist is incorrect. Both statements are false.
127. Which pair of monomers produces the polyester Dacron?
[AIPMT Chemistry — 2014]
(A) Propylene and hydroquinone
(B) Benzoic acid and ethanol
(C) Terephthalic acid and ethylene glycol
(D) Benzoic acid and hydroquinone
Answer: (C) Terephthalic acid and ethylene glycol
Explanation: Dacron, or polyethylene terephthalate, is formed by reacting terephthalic acid with ethylene glycol to create ester links along the polymer chain. The rigid aromatic units and repeating ester groups provide useful strength and dimensional stability for textile fibres and packaging applications.
126. Which artificial sweetener is mainly stable under cold conditions rather than high cooking temperatures?
[AIPMT Chemistry — 2014]
(A) Saccharin
(B) Sucralose
(C) Aspartame
(D) Alitame
Answer: (C) Aspartame
Explanation: Aspartame is a methyl ester of a dipeptide and can undergo hydrolysis or degradation on prolonged heating. Thus it is more suitable for cold foods and drinks than extended cooking. Saccharin and sucralose generally have better thermal stability in relevant applications.
125. Which of the following substances is a condensation polymer?
[JEE Main Offline Chemistry — 2014]
(A) Teflon
(B) Acrylonitrile
(C) Dacron
(D) Neoprene
Answer: (C) Dacron
Explanation: Dacron, a polyethylene terephthalate polyester, is classed as a condensation polymer formed from suitable diol and dicarboxylic-acid units. Teflon and neoprene form by chain-growth addition processes, while acrylonitrile is a monomer rather than the completed polymer.
124. Which reagent selectively oxidises a primary alcohol R–CH₂OH to an aldehyde R–CHO?
[JEE Main Offline Chemistry — 2014]
(A) Chromium trioxide
(B) Pyridinium chlorochromate
(C) Potassium permanganate
(D) Potassium dichromate
Answer: (B) Pyridinium chlorochromate
Explanation: Pyridinium chlorochromate, often abbreviated PCC, is a comparatively mild oxidising agent. Under anhydrous conditions it commonly stops oxidation of a primary alcohol at the aldehyde stage, whereas stronger aqueous oxidants may continue to the corresponding carboxylic acid.
123. ABS plastic is a:
[UPSC Engineering Services Mechanical — 2013, Paper 2]
(A) Monomer
(B) Copolymer
(C) Homopolymer
(D) Terpolymer
Answer: (D) Terpolymer
Explanation: ABS stands for acrylonitrile-butadiene-styrene. It contains three different monomer-derived components, so it is classified as a terpolymer. ABS is an engineering thermoplastic valued for impact resistance and processability; it is not a single monomer or homopolymer.
122. Euro vehicle-emission standards cover which gases?
[UPPSC Civil Service Prelims — 2013, Paper 1]
(A) Carbon monoxide
(B) Hydrocarbons
(C) Nitrogen oxides
(D) All of the above
Answer: (D) All of the above
Explanation: Vehicle emission standards regulate multiple pollutant categories, including carbon monoxide, unburned hydrocarbons and nitrogen oxides. Hydrocarbon emissions are particularly relevant to incomplete combustion of organic fuels. Their limits seek to reduce adverse impacts on air quality.
121. Consider:
1. Natural gas occurs in Gondwana beds.
2. Mica is abundant in Kodarma.
3. Dharwar rocks are famous for petroleum.
Which is correct?
[UPSC CSE Prelims — 2013]
(A) 1 and 2
(B) 2 only
(C) 2 and 3
(D) None
Answer: (B) 2 only
Explanation: Kodarma has historically been associated with mica deposits. Gondwana formations are best known for coal, whereas India’s principal conventional petroleum and natural gas basins occur in different geological settings. The Dharwar rock system is mineral-rich but not noted for petroleum deposits.
