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Part 050 – Chemistry Previous Year Questions

Q1. An inert gas mixed with oxygen given to patients suffering from restricted breathing is
(a) Helium (b) Krypton
(c) Radon (d) Argon
Ans: (a) Heliox is a breathing gas composed of a mixture of helium (He) and oxygen (O2). Heliox has been used medically since the 1930s, and although the medical community adopted it initially to alleviate symptoms of upper airway obstruction, its range of medical uses has since expanded greatly, mostly because of the low density of the gas

Q2. An example of major air pollutant is

(a) Oxygen
(b) Carbon monoxide
(c) Helium
(d) Carbon dioxide
Ans: (b) Carbon monoxide (CO) is a colourless, odorless, non-irritating but very poisonous gas which is a product by incomplete combustion of fuel such as natural gas, coal or wood. Vehicular exhaust is a major source of carbon monoxide.

Q3. The Fungus which is used in the alcohol industry is

(a) Mushroom
(b) Candida Aibicans
(c) Yeast
(d) Rhizopus
Ans: (c) Yeasts are eukaryotic microorganisms classified in the kingdom Fungi. By fermentation, the yeast species Saccharomyces cerevisiae converts carbohydrates to carbon dioxide and alcohols – for thousands of years the carbon dioxide has been used in baking and the alcohol in alcoholic beverages.

Q4. Gold dissolves in

(a) Hydrochloric acid
(b) Nitric acid
(c) Aqua-regia
(d) Acetic acid
Ans: (c) Aqua regia or nitro-hydrochloric acid is a highly corrosive mixture of acids, a fuming yellow or red solution. It was named so because it can dissolve the so-called royal or noble metals, gold and platinum.

Q5. Which halide is used in making sensitive emulsion on photograhic film?

(a) Sodium chloride
(b) Silver bromide
(c) Silver iodide
(d) Silver chloride
Ans: (b) Silver bromide, a soft, pale-yellow, water insoluble salt well known for its unusual sensitivity to light. This property has allowed silver halides to become the basis of modern photographic materials.

Q6. Among the following the hardest metal is

(a) Gold (b) Iron
(c) Platinum (d) Tungsten
Ans: (d) Titanium is the hardest natural metal in the world. It is very strong, three times the strength of steel and much stronger than gold, silver and platinum and yet is very light weight. Tungsten carbide is the hardest metal alloy on Earth and is scratch proof under normal wear. Tungsten carbide is two times as hard as steel and four times as hard as titanium.

Q7. The element used in the manufacture of safety matches is

(a) Phosphorous (b) Magnesium
(c) Silicon (d) Sulphur
Ans: (a) One end of a match is coated with a material that can be ignited by frictional heat generated by striking the match against a suitable surface. The coated end of a match, known as the match “head,” contains either phosphorus or phosphorus sesquisulfide as the active ingredient and gelatin as a binder.

Q8. The main source of Naphthalene is

(a) Charcoal (b) Camphor
(c) Coal-tar (d) Diesel
Ans: (c) The main source of Naphthalene is coal-tar. Naphthalene is derived from a kind of naphtha which is a broad term encompassing any volatile, flamable liquid hydrocarbon mixture, including coal-tar.

Q9. The material used in solar cells contains

(a) Tin (b) Silicon
(c) Caesium (d) Thallium
Ans: (b) A solar cell (also called a photovoltaic cell) is an electrical device that converts the energy of light directly into electricity by the photovoltaic effect. Materials presently used for photovoltaic solar cells include mono-crystalline silicon, polycrystalline silicon, amorphous silicon, cadmium telluride, and copper indium selenide/sulfide.

Q10. Quartz is a crystalline form of

(a) Alumina (b) Glass
(c) Silica (d) Limestone
Ans: (c) Quartz is made up of a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO2. Tridymite and cristobalite are hightemperature polymorphs of SiO2 that occur in highsilica volcanic rocks. Coesite is a denser polymorph of quartz found in some meteorite impact sites and in metamorphic rocks.

Q11. When lime juice is dropped on baking soda, brisk effervescence takes place because the gas evolved is

(a) Hydrogen (b) Oxygen
(c) Carbon dioxide
(d) All of them
Ans: (c) When baking soda and lemon juice are added together, the reaction of the two is an acid-based reaction because it involves an acid (citric acid in the lemon juice) reacting with a base (sodium bicarbonate, more commonly known as baking soda). Carbon dioxide, a gas, is produced by the reaction.

Q12. Which of the following is a super-
cooled liquid?

(a) Ice-cream (b) Ammonia
(c) Glass (d) Wood
Ans: (c) Glass is considered to be a super-cooled liquid due to its lack of a first-order phase transition where certain thermodynamic variables such as volume, entropy and enthalpy are discontinuous through the glass transition range. However, the glass transition may be described as analogous to a second-order phase transition where the intensive thermodynamic variables such as the thermal expansivity and heat capacity are discontinuous.

Q13. Which one of the following elements is least likely to be found in commercial fertilisers?

(a) Nitrogen (b) Phosphorous
(c) Potassium(d) Silicon
Ans: (d) Fertilizers typically provide, in varying proportions: (i) six macronutrients: nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and sulfur (S); and (ii) eight micronutrients: boron (B), chlorine (Cl), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), zinc (Zn) and nickel (Ni).

Q14. In the electroplating of gold, the electrolyte used is

(a) Gold chloride
(b) Gold nitrate
(c) Gold sulphate
(d) Potassium aurocyanide
Ans: (c) Gold plating is a method of depositing a thin layer of gold onto the surface of another metal, most often copper or silver (to make silver-gilt), by chemical or electrochemical plating. Electroplating of gold is done using a sulphate/sulfite based electrolyte. This product is environment- and user friendly and moreover the electroplating rate is good.

Q15. The acid present in red ants is

(a) Acetic acid
(b) Butyric acid
(c) Caproic acid
(d) Formic acid
Ans: (d) Formic acid is the simplest carboxylic acid. It is an important intermediate in chemical synthesis and occurs naturally, most notably in the venom of bee and ant stings. In fact, its name comes from the Latin word for ant, Formica, referring to its early isolation by the distillation of ant bodies.

Q16. The metal extracted from Bauxite is :

(a) Silver (b) Copper
(c) Manganese (d) Aluminum
Ans: (d) Bauxite is an aluminium ore and is the main source of aluminium. Approximately 70% to 80% of the world’s dry bauxite production is processed first into alumina, and then into aluminium by electrolysis as of 2010. Usually, bauxite ore is heated in a pressure vessel along with a sodium hydroxide solution at a temperature of 150 to 200 °C. At these temperatures, the aluminium is dissolved as an aluminate (the Bayer process).

Q17. pH value between 6.5-7.5 makes the soil

(a) Basic (b) Neutral
(c) Acidic (d) None of these
Ans: (d) In chemistry, pH is a measure of the activity of the (solvated) hydrogen ion. P (H), which measures the hydrogen ion concentration is closely related to, and is often written as, pH. Pure water has a pH very close to 7 at 25°C. Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline. A pH of 7 is treated as neutral.

Q18. The metal chiefly used for galvanising iron is :

(a) Zinc (b) Mercury
(c) Cadmium (d) Tin
Ans: (a) Galvanization is the process of applying a protective zinc coating to steel or iron, in order to prevent rusting. In current use, the term refers to the coating of steel or iron with zinc. This is done to prevent rusting of the ferrous item. The value of galvanizing stems from the corrosion resistance of zinc, which, under most service conditions, is considerably greater than that of iron and steel.

Q19. The wire of flash bulb is made of :

(a) Copper (b) Barium
(c) Magnesium (d) Silver
Ans: (c) The first modern photoflash bulb (or flashbulb) was made by Austrian Paul Vierkotter, who used magnesium coated wire in an evacuated glass globe. It was later determined that aluminum foil in a low pressure oxygen atmosphere worked even better, and was cheaper to produce.

Q20. The coloured discharge tubes for advertisement mainly contain

(a) Xenon (b) Argon
(c) Helium (d) Neon
Ans: (d) Neon gives a distinct reddish-orange glow when used in either low-voltage neon glow lamps or in highvoltage discharge tubes or neon advertising signs. The red emission line from neon is also responsible for the well known red light of helium-neon lasers. Neon is used in a few plasma tube and refrigerant applications but has few other commercial uses.

Q21. Muscle fatigue is caused by the accumulation of :

(a) Pyruvic acid
(b) Lactic acid
(c) Oxalacetic acid
(d) Uric acid
Ans: (b) It was once believed that lactic acid build-up was the cause of muscle fatigue. The assumption was lactic acid had a “pickling” effect on muscles, inhibiting their ability to contract. Produced as a by-product of fermentation, lactic acid can increase intracellular acidity of muscles. This can lower the sensitivity of contractile apparatus to Ca2+ but also has the effect of increasing cytoplasmic Ca2+ concentration through an inhibition of the chemical pump that actively transports calcium out of the cell. This counters inhibiting effects of potassium on muscular action potentials.

Q22. Baking soda is :

(a) Potassium carbonate
(b) Sodium hydroxide
(c) Sodium carbonate
(d) Sodium bicarbonate
Ans: (d) Baking Soda is Sodium bicarbonate or sodium hydrogen carbonate. It is primarily used in cooking (baking), as a leavening agent.

Q23. What is the most common salt in sea water ?

(a) Calcium carbonate
(b) Potassium chloride
(c) Sodium chloride
(d) Magnesium sulphate
Ans: (c) Sodium chloride, also known as salt, common salt, table salt or halite, is an ionic compound with the formula NaCl, representing equal proportions of sodium and chloride. Sodium chloride is the salt most responsible for the salinity of the ocean and of the extracellular fluid of many multi-cellular organisms.

Q24. When quick lime is added to water

(a) heat is liberated
(b) heat is absorbed
(c) temperature decreases
(d) no heat change takes place
Ans: (a) When quick lime is added to water, then a chemical reaction takes places and slaked lime is formed, evolving heat in this process. It makes the water boil. CaO + H2O Ca(OH)2 + heat

Q25. The number of neutrons present in an element having mass number 226 and atomic number 88 is :

(a) 88 (b) 138
(c) 314 (d) 50
Ans: (b) The mass number is a count of the number of particles in an atom’s nucleus which is made up of protons and neutrons. In other words, Mass Number = Number of Protons + Number of Neutrons. The atomic number is the number of protons in an atom of an element, i.e., 226 = 88 + number of Neutrons. So, the number of neutrons= 226 – 88= 138.

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