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Chemistry MCQs Based on Class XI NCERT
91. Consider the following statements: 1. Matter can be classified into three states- solid, liquid and gas. 2 An element contains particles of only one type which may be atoms only. 3. A mixture is formed where two or more atoms combine in a fix ratio to each other. Which of the above statement(s) is/are INCORRECT? a) 1 and 2 b 2 and 3 o None of the above All of the above
Solution: d Explanation: Matter can be classified into 4 states. Solid, liquid, Gas and Plasma. Elements contains particles of only one type which may be atoms or molecules Mixture has varying ratio, compounds have fixed ratio of atoms.
92. The atomic mass of an element is expressed as? 12 N isotope of Nitrogen b) 14 C isotope of Carbon e 12 C isotope of Oxygen ) 12 C isotope of Carbon
Solution: d Explanation: The atomic mass of an element is expressed relative to the 12 C isotope of Carbon which has a mass of 12u. Isotopes of an element differ in atomic mass only. They have same atomic number. They are of importance in Nuclear reactions, medical science etc.
93. In the molecule of C2H6 1. There are 2 moles of Carbon. 2. There are 6 atoms of Hydrogen. It is a compound. 4 It is a mixture. Select the correct answer using the code given below: a. 1 and 2 b. 2 and 3 C. All of the above d. None of these
o Solution: b Explanation: There are two atoms of Carbon in C2H6, not two moles. It is not a mixture as the ratio of Carbon and Hydrogen is fixed i.e. 2:6 21 6
94. What does the welding gas used for welding steel consists of? Carbon dioxide 2 Oxygen s) Hydrogen Nitrogen Select the correct answer using the code given below: ) 1 only 1 and 2 only 1, 2 and 3 only All of the above
Solution: d Explanation: These gases are used in a mixture. Most of these gases, in large quantities, would damage the weld, but when used in small, controlled quantities, can improve weld characteristics.
95. CHCh, a well nown compound is used as? o Heavy water in nuclear reactions b) Water purification e Air purification d) Anesthetic
Solution: d Explanation: CHCl3 is popularly known as Chloroform used as anesthetic in medical e science
96. 15 ppm (by mass) of impurity was found in drinking water. What does it mean? There are 15 atoms of impurity in water There are 15 parts per mole impurity in water. o There are 15 parts per million impurities in water. There are 15 parts per mass impurities in water.
97. Arrange the following in order of increasing molecular weights: a) H2O-CO2-CH4 b H20> CO2> CH4 H20 CO2 CH4
o Solution: d Explanation: Molar mass of H2O = 2* 1 + 16 =18 Molar mass of CH4-12 +4 = 16 Molar Mass of CO2 12+ 2 16-44 Molar mass of H20 116 18
Solution: c Explanation: More water added means more moles of water but simultaneously the volume of the water also increases, so the concentration remains constant. Concentration = moles of water/volume of water
Solution: c Explanation: In one molecule of Na2S04, there are 2 atoms of Na, one atom of S and 4 atoms of Oxygen.
100. There is 1 liter solution of diluted Sulphuric acid. If the volume is doubled, then the molarity of the solution will? a) ) Double the initial value o Same as the initial value Data is insufficient
o Solution: a Explanation: Molarity = Moles of Sulphuric acid/ volume = x/v Moles of Sulphuric acid is constant-x New molarity = x/2v Volume is doubled so molarity will be half.
101. Following is the Photosynthesis reaction 6CO2 + 6H20+ sunlight energy Cs12s+ 602 Now consider the following statements: Total number of Carbon atoms is 12. 2 Total number of Oxygen atoms is 18. a Chlorophyll absorbs mostly green light in the visible spectrum. 1. The reaction can happen artificially. Which of the above statements are INCORRECT? 1 and 2 2 and3 1 and 3 3 and 4
Solution: c Explanation: CH4 i.e. Methane, is a notorious greenhouse gas. C2H2 is Ethylene used in welding metals etc. Molecular mass of CH 12 +4-16 Molecular mass of C2H2-2*12+ 2= 26 Molecular mass of CH4 12 +4 16
Solution: 1 mole of water contains 6.022*1023 molecules. Each molecule of water contains 2 atoms of Hydrogen. Therefore, there are 2*6.022*1023 atoms = 12.046*1023 atoms of Hydrogen in 1 mole of water. Each molecule of
Solution b Explanation: The reaction is unbalanced as number of atoms of Oxygen in the reactant side is two, while in the product, number of Oxygen atoms is ten. Hence, it does not follow law of conservation of mass.
o Solution: a Explanation: As per the reaction one molecule of Nitrogen gives two molecules of . Ammonia (NH3). No of N2/ No of NH3 = 1: 2 Let no of moles of NH3 = x No of N2 = 0.5 mole, so x= 2* 0.5 = 1 mole
106. There is a solution of Hydrochloric acid of molarity 2M. Now consider the following statements: The solute is Hydrochloric acid. 2 Solution contains only Hydrochloric acid. 3 Solvent is water. There are two moles of Hydrochloric acid per liter of water. Select the correct answer using the code given below ) 1 and 2 and 3 1 and 3 2 d) 2, 3 and 4
Solution: a Explanation: Atom is the building blocks of elements. Although protons and electrons are smaller than atom, they do not react chemically, they act physically.
Solution: b Explanation: The experiment proved that the atom looked like a solar system. In the center was a positively charged nucleus and around it electrons revolved in their orbits.
110. Total number of electrons in one mole of Hydrogen will be? 2* Avogadro constant b) Avogadro constant e V2* Avogadro constant d) None of these
o Solution: a o Explanation: In one molecule of Hydrogen i.e. H2 there are two atoms of Hydrogen. e In one atom of Hydrogen there is 1 proton, 1 neutron in nucleus and 1 electron in orbit. In 1 mole of H2. there are 6.023* 1023 (Avogadro constant) molecules of Hydrogen. Atoms of Hydrogen in H22* Avogadro constant. Since 1 Hydrogen atom contains 1 electron. So total no of electrons = 1 * 2 * Avogadro constant.
111. Electron microscope is based on the principle of? a) Electronic theory b) Rutherford's experiment o Dual behavior of matter o Heliocentric theory
116. There is an element with atomic number 4 and atomic mass 9. Consider the following statements: The element is Beryllium denoted with symbol Be. 2 Number of electrons in its atom is 4 3 It is classified as alkaline earth metal. 4 It belongs to group 2 in the periodic table. Which of the above statements are INCORRECT? ) 1 and 2 b 2 and 3 o 1, 3 and 4 None of these
117. There are three light photons of different wavelengths. They are L1 L2, L3. If L1 < L2-L3, then the photon which will produce maximum energetic photoelectrons, when it strikes a solar cell will be (provided that every photon has threshold energy to produce photoelectron)? ) L1 b) L2 2 L3 c) ) All of them will produce same current
118. The Bromine atom possesses 35 electrons. How much electron it needs, to become stable during chemical reaction? 7 a) b) 2 c) d)
o Solution: b Explanation: The basic theme of organization of elements in the periodic table is to classify the elements in periods and groups according to their properties. This arrangement makes the study of elements and their compounds simple and systematic. In the periodic table, elements with similar properties are placed in the same group.
120. Which important property has been used by scientists to classify the elements into modern periodic table? Atomic weight b) Atomic number o Radioactivity Structure of atom
Solution: b Explanation: The modern periodic table lists the elements in order of increasing atomic number (the number of protons in the nucleus of an atom).