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Part 070 – Chemistry Previous Year Questions

Q1. Vinegar is __________ .
(a) diluted acetic acid
(b) glacial acetic acid
(c) glacial formic acid
(d) diluted formic acid
Ans: (d) Vinegar is mostly dilute acetic acid, often produced by fermentation and subsequent oxidation of ethanol. It is roughly 3–9% acetic acid by volume, making acetic acid the main component of vinegar apart from water.

Q2. What is the product formed when sodium bicarbonate is heated strongly?

(a) Sodium Carbonate
(b) Sodium Hydroxide
(c) Sodium Peroxide
(d) Sodium Monoxide
Ans: (a) When sodium bicarbonate is strongly heated, it decomposes into sodium carbonate, water vapor, and carbon dioxide. Solid sodium carbonate is a white powder and is used in cooking under the name ‘baking powder’; sodium bicarbonate is used in baking under the name ‘baking soda’. 2NaHCO3 (s) Na2CO3 (s) + CO2 (g) + H2O (g)

Q3. Sullage water is –

(a) waste water released from kitchen
(b) waste water released from toilets
(c) waste water released from factories
(d) waste water released from hospitals
Ans: (a) Sullage is a term used to describe wastewater that arises as a byproduct of daily human activities such as showering, washing kitchen utensils, and doing the laundry. It is used water that does not contain excreta. Sullage is commonly referred to as gray water that is a mixture of water, soap, detergent, bleach, dirt, and other compounds discarded after use.

Q4. The most pure form of Carbon among the options is

(a) Anthracite (b) Lampblack
(c) Graphite
(d) Wood Charcoal
Ans: (a) There are three forms of pure carbon: graphite, coal and diamond. Among coal, Anthracite has the highest carbon content, the fewest impurities, and the highest calorific content of all types of coal except for graphite. Anthracite is the most metamorphosed type of coal in which the carbon content is between 92.1% and 98%.

Q5. Warming Ammonium chloride with sodium hydrochloride in a test tube is an example of

(a) Open system
(b) Closed system
(c) Isobaric system
(d) Isothermal system
Ans: (a) When heated, ammonium chloride decomposes into ammonia and hydrogen chloride. The thermal decomposition of ammonium chloride is a reversible chemical change. On heating above 340°C, it decomposes to form two gases such as ammonia and hydrogen chloride. On cooling, the reaction is reversed and solid ammonium chloride is formed. The reaction is an example of an open system in which exchange of mass and energy takes place with the surroundings. NH4Cl(s) NH3(g)+HCl(g)

Q6. Calcium salts used as fertilizer is :

(a) Calcium Carbide
(b) Calcium Carbonate
(c) Calcium Cyanide
(d) Calcium Sulphate
Ans: (d) Sulphur (as sulphate) is a major plant nutrient, and is essential for crop growth. Calcium Sulphate (gypsum) is used to improve soil quality. Calcium sulphate acts as a pH buffer, which can contribute to neutralizing both soil alkalinity and acidity. It is mainly used for the reclamation of sodic soils through ion exchange (calcium replacing sodium).

Q7. Formic acid is produced by

(a) White ants
(b) Cockroaches
(c) Red ants (d) Mosquitoes
Ans: (c) Formic acid (HCO2H) occurs naturally, most notably in some ants. The word “formic” comes from the Latin word for ant, formica, referring to its early isolation by the distillation of ant bodies. It is this compound that causes most of the irritation that occurs immediately following an ant bite or a bee sting.

Q8. Which one of the following forms of phosphorus is most reactive?

(a) Black phosphorus
(b) White phosphorus
(c) Violet phosphorus
(d) Red phosphorus
Ans: (b) White phosphorus is the most reactive form of phosphorus. It is made up of discrete P4 tetrahedra which are subjected to very high angular strain as the angles is 60 degrees. This high angular strain makes white phosphorus unstable and highly reactive. It ignites spontaneously at about 50°C, and at much lower temperatures if finely divided.

Q9. Which is the heaviest metal among the following?

(a) Gold (b) Silver
(c) Iron (d) Copper
Ans: (a) The heaviness of any metal is defined with reference to high densities, atomic weights, or atomic numbers. The atomic masses of the given elements are: Gold: 196.96654; Silver: 107.8682; Copper: 63.546; Iron: 55.847. So the heaviest metal is gold, followed by silver, copper and iron.

Q10. Potassium Permanganate is used for purifying drinking water, because_________

(a) It is a reducing agent
(b) It is an oxidising agent
(c) It is a sterilising agent
(d) It dissolves the impurities of water
Ans: (b) Potassium permanganate is a point-of-entry water treatment method that oxidizes dissolved iron, manganese, and hydrogen sulfide into solid particles that are filtered out of the water. It can also be used to control iron bacteria growth in wells. It is an oxidant, but a poor disinfectant.

Q11. Atoms of same element having different mass numbers are called__________

(a) Isobars (b) Isotopes
(c) Isotones (d) Isomers
Ans: (b) Atoms that have the same atomic number but different atomic masses are called isotopes. The difference in mass arises due to the atoms containing a different number of neutrons for the same number of protons. For example, carbon-12, carbon-13 and carbon- 14 are three isotopes of the element carbon with mass numbers 12, 13 and 14 respectively.

Q12. Bee sting contains

(a) An acidic liquid
(b) a salt solution
(c) an alkaline liquid
(d) a corrosive liquid
Ans: (a) A bee sting is a sting from a bee (honey bee, bumblebee, sweat bee, etc.). Bee stings are acidic. So its effects can be neutralized with bicarbonate of soda or alkali and this reaction reduces the pain.

Q13. Highest percentage of carbon is found in which form of coal?

(a) Anthracite (b) Bituminous
(c) Peat (d) Lignite
Ans: (a) Anthracite is the highest rank of coal since it has a carbon content of over 87% on a dry ash-free basis. Anthracite coal generally has the highest heating value per ton on a mineral-matter-free basis. It has a bright luster and breaks with a semi-conchoidal fracture.

Q14. The chemical that is used to ripen mangoes is

(a) Calcium sulphide
(b) Calcium carbide
(c) Calcium carbonate
(d) Calcium chloride
Ans: (b) Calcium carbide is used for artificially ripening fruit. When calcium carbide comes in contact with moisture, it produces acetylene gas, which is quite similar in reaction to the natural ripening agent ethylene. Acetylene acts like ethylene and accelerates the ripening process.

Q15. Nylon threads are made of

(a) Polyester polymer
(b) Polyamide polymer
(c) Polyvinyl polymer
(d) Polysaccharide
Ans: (b) Nylon is a generic designation for a family of synthetic polymers, more specifically aliphatic or semiaromatic polyamides. They can be melt-processed into fibers, films or shapes. Nylon polymers have found significant commercial applications in fibers, in shapes and in films.

Q16. The manufacturing of iron from ironore involves the process of

(a) Oxidation
(b) Reduction
(c) Electrolysis
(d) Fractional distillation
Ans: (b) Iron is extracted from iron ore in a huge container called a blast furnace. Iron ores such as hematite contain iron oxide. The oxygen must be removed from the iron oxide to leave the iron behind. Reactions in which oxygen is removed are called reduction reactions. Both carbon and carbon monoxide are used in the reduction of the iron oxide (Fe2O3) to give iron. 2Fe2O3 + 3C 4Fe + 3CO2 Fe2O3 + 3CO 2Fe + 3CO2

Q17. An emulsion is a colloidal solution of

(a) Liquid in liquid
(b) Solid in liquid
(c) Gas in solid
(d) Solid in Solid
Ans: (a) An emulsion is a mixture of two or more liquids that are normally immiscible (unmixable or unblendable). Emulsions are part of a more general class of two-phase systems of matter called colloids. Examples of emulsions include vinaigrettes, homogenized milk, mayonnaise, and some cutting fluids for metal working.

Q18. _________ is a by product of sewage treatment and can be decomposed to produce biogas

(a) Sewage (b) Sludge
(c) Sewer (d) Scum
Ans: (b) Sludge refers to the residual, semi-solid material that is produced as a by-product during sewage treatment of industrial or municipal wastewater. It can be used to produce biogas through a process called anaerobic digestion or fermentation.

Q19. Bridgmanite is

(a) A bridge on the river Thames
(b) Name of a game
(c) Earth’s most abundant mineral
(d) Name of a music
Ans: (c) Bridgmanite is the accepted name for the mineral silicate perovskite, (Mg,Fe)SiO3, the most common mineral on Earth. It was discovered in Tenham chondrite meteorite, where it associates with another polymorph of MgSiO3 substance – akimotoite.

Q20. Synthetic detergents are prepared from

(a) potassium salts of higher fatty-
(b) sodium salts of higher fattyacids
(c) hydrocarbons of petroleum
(d) glycerides
Ans: (c) Synthetic detergents are prepared from hydrocarbons of petroleum. They are sodium salts of a long chain benzene sulphonic acids or sodium salts of long chain alkyl hydrogen sulphates. Calcium and magnesium salts of detergents are soluble in water. Therefore cleansing action of detergents remain unaffected in hard water.

Q21. Which one of the following is commonly used for pulp bleaching in the paper industry?

(a) Mild sulphuric acid
(b) Glucose isomerase
(c) Hydrogen peroxide
(d) Iodine and water
Ans: (c) Bleaching of wood pulp is the chemical processing carried out to decrease the color of the pulp, so that it becomes whiter.Alkaline hydrogen peroxide is the most commonly used bleaching agent for mechanical pulp. It selectively oxidizes non-aromatic conjugated groups responsible for absorbing visible light. The decomposition of hydrogen peroxide is catalyzed by transition metals.

Q22. The molecular mass of a gas is

(a) twice its vapour pressure
(b) equal to its vapour pressure
(c) half its vapour pressure
(d) not related to its vapour pressure
Ans: (a) The molecular weight (molar mass) of any gas is the mass of one particle of that gas multiplied by Avogadro’s number (6.02 × 1023). It is twice its vapor pressure since the molecular mass of any gas is twice its density in relation to hydrogen which has 2 atoms in one molecule.

Q23. Brown stains in vessels and clothes indicate the presence of high quantities of ______ in water

(a) Magnesium (b) Calcium
(c) Manganese (d) Chromium
Ans: (*) Brown stains in vessels and clothes generally indicate the presence of high quantities of iron. It causes reddish-brown staining of laundry, porcelain, dishes, utensils and even glassware. Manganese acts in a similar way but causes a brownish-black stain. Soaps and detergents do not remove these stains.

Q24. Which of the following gases is known as “Laughing Gas”?

(a) Nitrous oxide
(b) Nitrogen peroxide
(c) Nitrogen
(d) Nitric oxide
Ans: (a) Nitrous oxide (N2O) is commonly known as laughing gas. It is used in surgery and dentistry for its anaesthetic and analgesic effects. It is known as “laughing gas” due to the euphoric effects of inhaling it, a property that has led to its recreational use as a dissociative anaesthetic.

Q25. The ‘solid waste’ is also known as

(a) Sedge (b) Toxic waste
(c) Sludge (d) Scrubber
Ans: (c) Solid waste, also known as sludge, refers to the residual, semi-solid material that is produced as a by-product during sewage treatment of industrial or municipal wastewater. It mainly results from manufacturing process such as that of factories, industries, mills, and mining operations.

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