MCQ of Basic Concepts of Chemistry, Class 11, Chemistry
Question 1: Mark the rule which is not correctly stated about the determination of significant figures.
- Zeros preceding to first non zero digit are not significant
- Zeros between two non zero digits are not significant
- Zeros at the end or right of the number are significant if they are on the right side of the decimal point
- All non zero digits are significant
Answer: B ( Zeros between two non zero digits are not significant )
Question 2: Which of the following rules regarding the significant figures and calculations involving them is not correct?
- The result of an addition or subtraction is reported to the same number of decimal places as present in number with least decimal places.
- Result of multiplication or division should have same number of significant figures as present in most precise figure
- The result of multiplication or division should be rounded off to same number of significant figures as present in least precise figure
- The non significant figures in the measurements are rounded off
Answer: B (Result of multiplication or division should have same number of significant figures as present in most precise figure)
Question 3: Few figures are expressed in specific notations. mark the incorrect one.
- 234000 = 2.34 × 105
- 8008 = 8 × 103
- 0.0048 = 4.8 × 10-3
- 500.0 = 5.00 × 102
Answer: B (8008 = 8 × 103)
Question 4: 4.88 g of KClO3 when heated produced 1.92 g of O2 and 2.96 g of KCl. Which of the following statements regarding the experiment is correct?
- The result illustrates the law of conservation of mass
- The result illustrates the law of multiple proportions
- The result illustrates the law of constant proportion
- None of the above laws is followed
Answer: A (The result illustrates the law of conservation of mass)
Question 5: How much mass of silver nitrate will react with 5.85 g of sodium chloride to produce 14.35 g of silver chloride and 8.5 g sodium nitrate if law of conservation of mass is followed?
- 22.85 g
- 108 g
- 17.0 g
- 28.70 g
Answer: C (17.0 g)
Question 6: Which of the following statements best explains the law of conservation of mass?
- 100 g of water is heated to give steam
- A sample of N2 gas is heated at constant pressure without any change in mass
- 36 g of carbon combines with 32 g of oxygen to form 68 g of CO2
- 10 g of carbon is heated in vacuum without any change in mass
Answer: C (36 g of carbon combines with 32 g of oxygen to form 68 g of CO2)
Question 7: What mass of sodium chloride would be decomposed by 9.8 g of sulphuric acid if 12 g of sodium bisulphate and 2.75 g of hydrogen chloride were produced in a reaction?
- 14.75 g
- 3.8 g
- 4.95 g
- 2.2 g
Answer: C (4.95 g)
Question 8: In an experiment, 2.4 g of iron oxide on reduction with hydrogen gave 1.68 g of iron. In another experiment 2.7 g of iron oxide gave 1.89 g of iron on reduction. Which law is illustrated from the above data?
- Law of constant proportions
- Law of multiple proportions
- Law of conservation of mass
- None of these
Answer: A ( Law of constant proportions)
Question 9: Which of the following statements illustrates the law of multiple proportions?
- An element forms two oxides, XO and X2O containing 50% and 60% oxygen respectively. The ratio of masses of oxygen which combines with 1 g of element is 2 : 3.
- One volume of nitrogen always combines with three volume of oxygen to form two volumes of ammonia
- 3.74 g of BaCl2 reacts with 2.36 g of Na2SO4 to give 3.88 g of BaSO4 and 1.95 g of NaCl
- 20 mL of ammonia gives 10 volumes of N2 and 30 volumes of H2 at constant temperature and pressure.
Answer: A (An element forms two oxides, XO and X2O containing 50% and 60% oxygen respectively. The ratio of masses of oxygen which combines with 1 g of element is 2 : 3.)
Question 10: The statements for law of chemical combination are given below.
- Matter can neither be created nor destroyed : Law of conservation of mass
- A compound always contains exactly the same proportions of elements by weight: Law of definite proportions
- When gases combines they do so in a simple ratio by weight: Gay Lussac’s Law
- Equal volumes of gases at same temperature and pressure contain same number of molecules: Avogadro’s Law
Answer: C (When gases combines they do so in a simple ratio by weight: Gay Lussac’s Law)
You may also read MCQ of Structure of Atom, MCQ of Classification of Elements and Periodicity in Properties, MCQ of Chemical Bonding and Molecular Structure, MCQ of States of Matter, MCQ of Redox Reactions, MCQ of Hydrogen, MCQ of Organic Chemistry; Some Basic Principles and Techniques for better understanding of the chapters.
Question 11: Given below are a few statements. Mark the statement which is not correct.
- Atoms are neither created nor destroyed in a chemical reaction
- Law of definite proportions states that a given compound always contains exactly the same proportion of elements by weight
- Gay lussac’s law of chemical combination is valid for all substances
- A compound has always a fixed proportion of masses of its constituents
Answer: C (Gay lussac’s law of chemical combination is valid for all substances)
Question 12: Which of the following statements about Avogadro’s hypothesis is correct?
- Under similar condition of temperature and pressure gases react with each other in simple ratio.
- Under similar conditions of temperature and pressure equal volumes of all gases contain same number of molecules
- At NTP all gases contains same number of molecules
- Gases always react with gases only at the given temperature and pressure
Answer: B ( Under similar conditions of temperature and pressure equal volumes of all gases contain same number of molecules)
Question 13: Which of the following postulates of Dalton’s atomic theory explains the law of multiple proportions?
- Atoms of two elements may combine with one another to form more than one compound
- Atoms combine in the ratio of small whole numbers to form compounds
- The relative number and kinds of atoms are constant in a given compound
- All of the above
Answer: B (Atoms combine in the ratio of small whole numbers to form compounds)
Question 14: The main drawback of Dalton’s atomic theory is
- It could not explain the law of gaseous volume
- It could not explain why atoms of different elements have different masses, sizes, etc
- It could not explain how and why atoms combine to form molecules
- All of the above
Answer: D (All of the above)
Question 15: The mass of one mole of a substance in grams is called its
- Molecular mass
- Molar mass
- Avogadro’s mass
- Formula mass
Answer: B (Molar mass)
Question 16: 0.48 g of a sample of compound containing boron and oxygen contains 0.192 g of boron and 0.288 g oxygen. What will be the percentage composition of the compound?
- 60% and 40% B and O respectively
- 40% and 60% B and O respectively
- 30% and 70% B and O respectively
- 70% and 30% B and O respectively
Answer: B (40% and 60% B and O respectively)
Question 17: A compound of magnesium contains 21.9% magnesium, 27.8% phosphorus and 50.3% oxygen. What will be the simplest formula of the compound?
Answer: A (Mg3P2O7)
Question 18: A compound contains C = 40% , H= 13.33% and N = 46.67% . Its empirical formula is
Answer: C (CH4N)
Question 19: Two elements ‘P’ and ‘Q’ combine to form a compound. Atomic mass of ‘P’ is 12 and ‘Q’ is 16. Percentage of P in the compound is 27.3. what will be the empirical formula of the compound?
Answer: D (PQ2)
Question 20: 1g of Mg is burnt in a closed vessel containing 0.5 g of O2. Which reactant is limited reagent and how much of excess reactant will be left?
- O2 is a limiting reagent and Mg is in excess by 0.25 g.
- Mg is a limiting reagent and O2 is in excess by 0.5 g.
- O2 is a limiting reagent and Mg is in excess by 0.05 g.
- O2 is a limiting reagent and Mg is in excess by 0.75 g
Answer: A (O2 is a limiting reagent and Mg is in excess by 0.25 g.)
Question 21: How much moles of Oxygen gas can be produced during electrolytic decomposition of 180 g of water?
- 2.5 moles
- 5 moles
- 10 moles
- 7 moles
Answer: B (5 moles)
Question 22: How much oxygen is required for complete combustion of 560 g of ethene?
- 6.4 kg
- 1.92 kg
- 2.8 kg
- 9.6 kg
Answer: B (1.92 kg)
Question 23: In a reaction container, 100 g of hydrogen and 100 g of Cl2 are mixed for the formation of HCl gas. What is limiting reagent and how much HCl is found in the reaction?
- H2 is a limiting reagent and 36.5 g of HCl is formed
- Cl2 is a limiting reagent and 102.8 g of HCl is formed
- H2 is a limiting reagent and 142 g of HCl is formed
- Cl2 is a limiting reagent and 73 g of HCl is formed
Answer: B ( Cl2 is a limiting reagent and 102.8 g of HCl is formed)
Question 24: A solution is prepared by adding 5 g of a solute ‘X’ to 45 g of solvent ‘Y’. What is the mass percent of the solute ‘X’?
- 10 %
- 11.1 %
- 90 %
- 75 %
Answer: A (10 %)
Question 25: 2.82 g of glucose is dissolved in 30 g of water. The mole fraction of glucose in the solution is
Answer: A (0.01)
Question 26: The final molarity of a solution made by mixing 50 mL of 0.5 M HCl, 150 mL of 0.25 M HCl and water to make the volume 250 mL is
- 0.5 M
- 1 M
- 0.75 M
- 0.25 M
Answer: D (0.25 M)
Question 27: Which mode of concentration does not change with temperature?
- All of these
Answer: C ( Molality)
Question 28: What will be the molality of chloroform in the water sample which contains 15 ppm chloroform by mass?
- 1.25 × 10-4 m
- 2.5 × 10-4 m
- 1.5 × 10-3 m
- 1.25 × 10-5 m
Answer: A (1.25 × 10-4 m )
Question 29: A solution is made by dissolving 49 g of H2SO4 in 250 mL of water. The molarity of the solution prepared is
- 2 M
- 1 M
- 4 M
- 5 M
Answer: A (2 M)
Question 30: 4.28 g of NaOH is dissolved in water and the solution is made to 250 cc. What will be the molarity of the solution?
- 0.615 mol L-1
- 0.428 mol L-1
- 0.99 mol L-1
- 0.301 mol L-1
Answer: B (0.428 mol L-1)
Question 31: Which of the following statements about compound is incorrect?
- A molecule of a compound has atoms of different elements
- A compound cannot be separated into its constituent elements by physical method of preparation
- A compound retains the physical properties of its constituent elements
- The ratio of atoms of different elements in a compound is fixed
Answer: C (A compound retains the physical properties of its constituent elements)
Question 32: If 500 mL of a 5 M solution is diluted to 1500 mL, what will be the molarity of the solution obtained?
- 1.5 M
- 1.66 M
- 0.017 M
- 1.59 M
Answer: B (1.66 M)
Question 33: If the concentration of glucose in blood is 0.9 g L-1. What will be the molarity of glucose in blood?
- 5 M
- 50 M
- 0.005 M
- 0.5 M
Answer: C (0.005 M)
Question 34: What will be the molality of the solution containing 18.25 g of HCl gas in 500 g of water?
- 0.1 m
- 1 M
- 0.5 m
- 1 m
Answer: D (1 m)
Question 35: Which of the following statement is correct about the following reaction: 4 Fe + 3O2 →2Fe2O3
- Total mass of iron and oxygen in reactants = total mass of iron and oxygen in product; therefore it follows law of conservation of mass.
- Total mass of reactant= total mass of product; law of multiple proportions is followed
- Amount of Fe2O3 can be increased by taking any one of the reactants (iron or oxygen) in excess.
- Amount of Fe2O3 produced will decrease If the amount of any one of the reactants ( iron oxygen) is taken in excess.
Answer: A ( Total mass of iron and oxygen in reactants = total mass of iron and oxygen in product; therefore it follows law of conservation of mass.)
Question 36: Which of the following statements indicates the law of multiple proportions is being followed?
- Sample of carbon dioxide taken from any source will always have carbon and oxygen in the ratio 1 : 2.
- Carbon form two oxides namely CO2 and CO where masses of oxygen which combine with fixed masses of carbon are in the simple ratio 2 : 1
- When magnesium burns in oxygen the amount of magnesium taken for the reaction is equal to the amount of magnesium in magnesium oxide formed.
- At constant temperature and pressure 200 mL of hydrogen will combine with 100 mL oxygen to produce 200 mL of water vapour.
Answer: B (Carbon form two oxides namely CO2 and CO where masses of oxygen which combine with fixed masses of carbon are in the simple ratio 2 : 1)
Question 37: In an experiment it showed that 10 mL of 0.05 M solution of chloride required 10 mL of 0.1 M solution of AgNO3, which of the following will be the formula of chloride ( X stands for the symbol of the element other than chlorine)?
Answer: B (XCl2)
Question 38: One gram of Na2CO3 and NaHCO3 consumes y gram equivalent of HCl for complete neutralization. One gram of the mixture is strongly heated, then food and the residue treated with HCl. The gram equivalent of HCl now required for complete neutralization will be
- 2 y
- 3 y
- y / 2
Answer: C (y)
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