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Chemistry MCQs Based on Class XI NCERT
151. pH of sea water will be? Equal to 7 Less than 7 o More than 7 d)
Solution: c o Explanation: Sea water is slightly basic in nature. Basic solutions have pH value more than 7. acidic solutions have less than 7 pH value. Neutral solutions have pH 7.
152. Why is sea water basic in nature? a) Because sea absorbs Carbon Dioxide b) Eggshells, snail shells and most seashells are predominantly Calcium a . Carbonates e Lot of salts of Magnesium and Calcium are dissolved in it. d) All of the above
Solution: b Explanation: Presence of CO2 makes water acidic as CO2 forms Carbonic acid with water. But, there are lot of Carbonates released in sea water that come from organisms etc. This Carbonate reacts with water to release Hydroxyl ions making it basic. Na.CO. + H2O NaOH + H2CO2
153. Salts formed form the reaction of a strong acid and a strong base is? a Acidic b) Neutral o Basic ) Depends on the acid used
o Solution: b Explanation: When strong acids and strong bases react, the products are salt and water. The acid and base neutralize each other, so the solution will be neutral (pH=7) and the ions that are formed will not react with the water Example: NaOH + HCl NaCl + H2O
154. The pH of a solution is the? a Concentration of Hydronium ions b Concentration of Hydroxyl ions Negative logarithm of concentration of Hydrogen ions o Logarithm of concentration of Hydrogen ions
Solution: c Explanation Ph =-log(H+ions concentration)
155. Protium, Tritium and Deuterium are the isotopes of Hydrogen. Consider the following statements Protium is radioactive 2 Deuterium is used to make heavy water. a Hydrogen is the most abundant element in the universe. Which of the above is/are true? ) 1 and2 2 and3 1 only o All of these ) 1 only
o Solution: b Explanation: Tritium is the only radioactive isotope of Hydrogen. D20 is the formula of heavy water used in nuclear reactors. Hydrogen is the star forming material in the universe.
156. The term Hydrogen Economy refers to? a Economy dealing in Hydrogen footprints instead of paper money b) Hydrogen reserves of a country being used as a measure for development o System of using Hydrogen as rocket fuel. System of delivering energy using Hydrogen.
157. Water is a very good solvent because? a It is tetrahedral in shape. b) It readily dissolves salts in it. It forms metallic bond with solute. o It has polar nature.
o Solution: d Explanation e Water is of polar nature means it has partial positive and negative charge on it. Therefore, it attracts anions and cations of the solute particles forming bonds with them.
Solution: c Explanation: Ice molecule is a crystalline water molecule which is tetrahedral in nature.
Solution: d Explanation: e Self-explanatory
160. Use of Zeolite with water can remove? a) Permanent hardness ) Temporary hardness o Both a and b d) None
o Solution: c Explanation: Zeolites are large group of minerals consisting of hydrated Aluminosilicates of Sodium, Potassium, Calcium and Barium They can be readily dehydrated and rehydrated and are used as cation exchangers, molecular sieves and for removing water hardness.
161. A compound made up of Oxygen and Hydrogen is used as an industrial bleach. It is also used in pharmaceutical industry and pollution control treatment of industrial and domestic effluents. The compound is? a) H2O b) H3O+ H2O2 o) D20
o Solution: d o E Explanation: If used in a cramp space like a server room, CO2 can asphyxiate people. . Carbon dioxide extinguishers work by suffocating the fire. Carbon dioxide displaces Oxygen in the air.
Solution: d o Explanation: Syngas, or synthesis gas, is a fuel gas mixture consisting primarily of Hydrogen, Carbon monoxide and very often some Carbon dioxide. The name comes from its use as intermediates in creating Synthetic Natural Gas (SNG) and for producing Ammonia or Methanol.
Solution: b Explanation: Environmental pollution mostly happens in troposphere and e stratosphere. Ozone destruction happens in stratosphere.
o Solution: d Self-explanatory
166. Liquefied Carbon dioxide is used as? 1 Fire extinguisher Dye 2. 3. Refrigerant Dry cleaning Select the correct answer using the code given below: 1 and 2 b 2 and 3 1, 3 and 4 All of the above
s Solution: c Explanation: Self-explanatory
o Solution: c Explanation: o The metathesis is a method used in organic synthesis. It has tremendous potential in the pharmaceutical, environment - friendly polymers It is a great step in green chemistry
170. Dinitrogen and dioxygen are the main constituents of air. Consider the following statements: onser ing tol owg tagen ents the main constituents of ai. These gases do not react with each other. 2 Lightening strikes at high altitude which causes them to combine. Nitrogen oxides serves as a fertilizer. Select the correct answer using the code given below: 1 and 2 2 and 3 1 and 3 b) o 2 only
Solution: d N2 and O2 are non reactive at normal temperature. But at higher alitude when lig But at higher altitude when lightening strikes, they combine to form oxides of Nitrogen. oxides of Nitrogen are not fertilizer but Nitrate is (NO3).
171. The pH of Acid-rain is? Less than 10 Less than 7 Less than 5.6 Less than 7.6 o Less than 7.6 d)
176. Why ozone hole is specifically found over the south pole? Presence of polar wind. b Presence of polar stratospheric clouds. Presence of chlorofluorocarbon over south pole. a Ozone layer is very thin over south pole.
Solution: a The amount of BOD in water is a measure of the amount of organic material in the water, in terms of how much Oxygen will be required to break it down biologically. e
Solution: b Explanation: Clear water has BOD value less than 5 ppm. Highly polluted water has BOD value of 17 or more.
180. Fluoride in water causes? b) Tooth decay b) Strong Enamel o Both a and b d) None of these
Solution: c Explanation: Up to 1 ppm fluoride in drinking water makes the enamel of the teeth much harder However, the excess of fluoride ion above 2 ppm causes browrn mottling of teeth. Over 10 ppm fluoride decays teeth and bones, as reported from some e parts of Rajasthan.