Q.1.<\/strong> What is the SI unit of amount of substance? (a) Kilogram (b) Mole (c) Pascal (d) Kelvin<\/p>\n\n\n\n Answer: (b) Mole<\/strong> Detailed Answer:<\/strong> The International System of Units (SI) has seven base units. The unit for the amount of substance is the mole (mol)<\/strong>. Kilogram (kg) is the unit for mass, Pascal (Pa) for pressure, and Kelvin (K) for thermodynamic temperature.<\/p>\n\n\n\n Q.2.<\/strong> How many significant figures are present in the measurement 0.00250? (a) Five (b) Four (c) Three (d) Two<\/p>\n\n\n\n Answer: (c) Three<\/strong> Detailed Answer:<\/strong> The rules for significant figures are:<\/p>\n\n\n\n Q.3.<\/strong> Which law of chemical combination is best illustrated by the formation of Carbon Monoxide (CO) and Carbon Dioxide (CO2\u200b)? (a) Law of Conservation of Mass (b) Law of Constant Proportions (c) Law of Multiple Proportions (d) Gay-Lussac’s Law of Gaseous Volumes<\/p>\n\n\n\n Answer: (c) Law of Multiple Proportions<\/strong> Detailed Answer:<\/strong> The Law of Multiple Proportions states that if two elements can combine to form more than one compound, the masses of one element that combine with a fixed mass of the other element are in a ratio of small whole numbers.<\/p>\n\n\n\n Q.4.<\/strong> What is the mass of one molecule of glucose (C6\u200bH12\u200bO6\u200b) in grams? (Atomic masses: C=12 u, H=1 u, O=16 u; NA\u200b=6.022\u00d71023) (a) 180 g (b) 3.0\u00d710\u221222 g (c) 1.66\u00d710\u221224 g (d) 2.99\u00d710\u221223 g<\/p>\n\n\n\n Answer: (d) 2.99\u00d710\u221223 g<\/strong> Detailed Answer:<\/strong><\/p>\n\n\n\n Q.5.<\/strong> Which of the following is an example of a homogeneous mixture? (a) Sand and water (b) Sugar solution (c) Oil and water (d) Copper fillings and sulphur powder<\/p>\n\n\n\n Answer: (b) Sugar solution<\/strong> Detailed Answer:<\/strong> A homogeneous mixture<\/strong> is a mixture in which the components mix uniformly, and the composition is the same throughout the mixture. A sugar solution (sugar dissolved in water) is an example of a homogeneous mixture. The other options are examples of heterogeneous mixtures, where the components remain separate.<\/p>\n\n\n\n Q.6.<\/strong> The empirical formula of a compound is CH2\u200bO, and its molecular mass is 180 g. What is its molecular formula? (a) CH2\u200bO (b) C6\u200bH12\u200bO6\u200b (c) C2\u200bH4\u200bO2\u200b (d) C3\u200bH6\u200bO3\u200b<\/p>\n\n\n\n Answer: (b) C6\u200bH12\u200bO6\u200b<\/strong> Detailed Answer:<\/strong><\/p>\n\n\n\n Q.7.<\/strong> The maximum number of molecules is present in: (a) 15 L of H2\u200b gas at STP (b) 5 L of N2\u200b gas at STP (c) 0.5 g of H2\u200b gas (d) 10 g of O2\u200b gas<\/p>\n\n\n\n Answer: (a) 15 L of H2\u200b gas at STP<\/strong> Detailed Answer:<\/strong> The number of molecules is directly proportional to the number of moles.<\/p>\n\n\n\n Q.8.<\/strong> Molarity is defined as: (a) Moles of solute per kg of solvent. (b) Moles of solute per L of solution. (c) Grams of solute per L of solution. (d) Grams of solute per kg of solvent.<\/p>\n\n\n\n Answer: (b) Moles of solute per L of solution.<\/strong> Detailed Answer:<\/strong> Molarity (M) is a measure of the concentration of a solute in a solution, defined as the number of moles of solute dissolved per litre of the solution<\/strong>.<\/p>\n\n\n\n Molarity(M)=Volume of solution in litresMoles of solute\u200b<\/p>\n\n\n\n Q.9.<\/strong> Which of the following concentration terms is independent of temperature? (a) Molarity (b) Normality (c) Molality (d) Volume percentage<\/p>\n\n\n\n Answer: (c) Molality<\/strong> Detailed Answer:<\/strong><\/p>\n\n\n\n Q.10.<\/strong> 4 L of N2\u200b gas reacts with 9 L of H2\u200b gas to form ammonia (NH3\u200b). What is the maximum volume of NH3\u200b that can be formed? (Assume the reaction occurs at constant temperature and pressure). The balanced reaction is: N2\u200b(g)+3H2\u200b(g)\u21922NH3\u200b(g) (a) 4 L (b) 6 L (c) 8 L (d) 12 L<\/p>\n\n\n\n Answer: (b) 6 L<\/strong> Detailed Answer:<\/strong> The problem involves Gay-Lussac’s Law of Gaseous Volumes and the concept of Limiting Reagent. The volume ratios are the same as the mole ratios.<\/p>\n\n\n\n Ratio (Volume):Initial Volume:\u200bN2\u200b(g)14 L\u200b+:\u200b3H2\u200b(g)39 L\u200b\u2192:\u200b2NH3\u200b(g)20 L\u200b<\/p>\n\n\n\n Q.11.<\/strong> How many atoms are present in 46 g of sodium (Na)? (Atomic mass of Na=23 u; NA\u200b=6.022\u00d71023 atoms\/mol) (a) 6.022\u00d71023 (b) 1.2044\u00d71024 (c) 2.4088\u00d71024 (d) 3.011\u00d71023<\/p>\n\n\n\n Answer: (b) 1.2044\u00d71024<\/strong> Detailed Answer:<\/strong><\/p>\n\n\n\n Q.12.<\/strong> The temperature of a substance is 25\u2218C. What is this temperature on the Kelvin scale? (a) 298.15 K (b) 25 K (c) 248.15 K (d) 273.15 K<\/p>\n\n\n\n Answer: (a) 298.15 K<\/strong> Detailed Answer:<\/strong> The relationship between the Celsius scale (\u2218C) and the Kelvin scale (K) is:<\/p>\n\n\n\n Temperature in K=Temperature in \u2218C+273.15<\/p>\n\n\n\n Temperature in K=25+273.15=298.15 K<\/p>\n\n\n\n Q.13.<\/strong> What is the mass percent of oxygen in water (H2\u200bO)? (Atomic masses: H=1.0 u, O=16.0 u) (a) 88.89% (b) 11.11% (c) 66.66% (d) 33.33%<\/p>\n\n\n\n Answer: (a) 88.89%<\/strong> Detailed Answer:<\/strong><\/p>\n\n\n\n Q.14.<\/strong> Which of the following is a unit of density? (a) kg\u22c5m (b) g\u22c5L (c) g\/cm3 (d) mol\/L<\/p>\n\n\n\n Answer: (c) g\/cm3<\/strong> Detailed Answer:<\/strong> Density is defined as mass per unit volume.<\/p>\n\n\n\n Density=VolumeMass\u200b<\/p>\n\n\n\n Q.15.<\/strong> When 2.0 L of a 5 M solution is diluted to 10.0 L, what is the final molarity of the solution? (a) 1.0 M (b) 0.5 M (c) 2.5 M (d) 0.1 M<\/p>\n\n\n\n Answer: (a) 1.0 M<\/strong> Detailed Answer:<\/strong> This is a dilution problem, which follows the formula:<\/p>\n\n\n\n M1\u200bV1\u200b=M2\u200bV2\u200b<\/p>\n\n\n\n Where:<\/p>\n\n\n\n Q.16.<\/strong> Which statement about the Law of Conservation of Mass is correct? (a) Mass can be created but not destroyed. (b) The total mass of reactants is less than the total mass of products. (c) Matter can neither be created nor destroyed. (d) The mass of the system remains unchanged in a physical change only.<\/p>\n\n\n\n Answer: (c) Matter can neither be created nor destroyed.<\/strong> Detailed Answer:<\/strong> The Law of Conservation of Mass (or Matter) states that in a closed system, the mass of the system remains constant, meaning matter can neither be created nor destroyed<\/strong> by any physical or chemical change. In a chemical reaction, the total mass of the reactants must equal the total mass of the products.<\/p>\n\n\n\n Q.17.<\/strong> How many moles of methane (CH4\u200b) are required to produce 22 g of CO2\u200b upon complete combustion? (Atomic masses: C=12 u, O=16 u) (a) 1.0 mol (b) 0.5 mol (c) 2.0 mol (d) 0.25 mol<\/p>\n\n\n\n Answer: (b) 0.5 mol<\/strong> Detailed Answer:<\/strong><\/p>\n\n\n\n Q.18.<\/strong> The number of significant figures in Avogadro’s number (6.022\u00d71023) is: (a) 26 (b) 23 (c) 4 (d) 1<\/p>\n\n\n\n Answer: (c) 4<\/strong> Detailed Answer:<\/strong> In scientific notation, all digits in the mantissa (the part before the power of 10) are considered significant figures.<\/p>\n\n\n\n Q.19.<\/strong> 1\u00a0amu (atomic mass unit) is equal to: <\/p>\n\n\n\n (a) 161\u200b of the mass of an oxygen atom<\/p>\n\n\n\n (b) The mass of a proton <\/p>\n\n\n\n (c) 121\u200b of the mass of a C-12 isotope atom <\/p>\n\n\n\n (d) The mass of a hydrogen atom<\/p>\n\n\n\n Answer: (c) 121\u200b of the mass of a C-12 isotope atom<\/strong> Detailed Answer:<\/strong> The atomic mass unit (amu) or unified mass (u) is defined as exactly one-twelfth (1\/12) of the mass of an atom of carbon-12<\/strong> isotope.<\/p>\n\n\n\n Q.20.<\/strong> Which of the following prefixes corresponds to 10\u22129? (a) Mega (b) Giga (c) Nano (d) Micro<\/p>\n\n\n\n Answer: (c) Nano<\/strong> Detailed Answer:<\/strong><\/p>\n\n\n\n Some basic concept of chemistry Class 11 Chemistry: Chapter 1 – Some Basic Concepts of Chemistry (20 MCQs) Q.1. What is the SI unit of…<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-705","post","type-post","status-publish","format-standard","hentry","category-uncategorized"],"_links":{"self":[{"href":"https:\/\/vracademy.in\/index.php?rest_route=\/wp\/v2\/posts\/705","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/vracademy.in\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/vracademy.in\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/vracademy.in\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/vracademy.in\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=705"}],"version-history":[{"count":2,"href":"https:\/\/vracademy.in\/index.php?rest_route=\/wp\/v2\/posts\/705\/revisions"}],"predecessor-version":[{"id":707,"href":"https:\/\/vracademy.in\/index.php?rest_route=\/wp\/v2\/posts\/705\/revisions\/707"}],"wp:attachment":[{"href":"https:\/\/vracademy.in\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=705"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/vracademy.in\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=705"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/vracademy.in\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=705"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
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