PYQ Vault

Chemistry · Textbook solutions

Some Basic Concepts of Chemistry

Every solved example, exercise, and miscellaneous question — in the order the textbook teaches them. · 74 questions

Worked Examples

8 q

Solved Examples

Worked · 8
  1. Eg 1.1
    Calculate the molecular mass of glucose (C6H12O6)\left(\text{C}_6\text{H}_{12}\text{O}_6\right) molecule.
  2. Eg 1.2
    A compound contains 4.07% hydrogen, 24.27% carbon and 71.65% chlorine. Its molar mass is 98.96 g98.96\,\text{g}. What are its empirical and molecular formulas?
  3. Eg 1.3
    Calculate the amount of water (g) produced by the combustion of 16 g16\,\text{g} of methane.
  4. Eg 1.4
    How many moles of methane are required to produce 22 g22\,\text{g} CO2(g)\text{CO}_2(g) after combustion?
  5. Eg 1.5
    50.0 kg50.0\,\text{kg} of N2(g)\text{N}_2(g) and 10.0 kg10.0\,\text{kg} of H2(g)\text{H}_2(g) are mixed to produce NH3(g)\text{NH}_3(g). Calculate the amount of NH3(g)\text{NH}_3(g) formed. Identify the limiting reagent in the production of NH3\text{NH}_3 in this situation.
  6. Eg 1.6
    A solution is prepared by adding 2 g2\,\text{g} of a substance A to 18 g18\,\text{g} of water. Calculate the mass per cent of the solute.
  7. Eg 1.7
    Calculate the molarity of NaOH in the solution prepared by dissolving its 4 g4\,\text{g} in enough water to form 250 mL250\,\text{mL} of the solution.
  8. Eg 1.8
    The density of 3 M3\,\text{M} solution of NaCl is 1.25 g mL−11.25\,\text{g mL}^{-1}. Calculate the molality of the solution.

Exercises

66 q
  1. Ex 1.1(i)
    Calculate the molar mass of the following: (i) H2O\text{H}_2\text{O}
  2. Ex 1.1(ii)
    Calculate the molar mass of the following: (ii) CO2\text{CO}_2
  3. Ex 1.1(iii)
    Calculate the molar mass of the following: (iii) CH4\text{CH}_4
  4. Ex 1.2
    Calculate the mass per cent of different elements present in sodium sulphate (Na2SO4)\left(\text{Na}_2\text{SO}_4\right).
  5. Ex 1.3
    Determine the empirical formula of an oxide of iron, which has 69.9% iron and 30.1% dioxygen by mass.
  6. Ex 1.4(i)
    Calculate the amount of carbon dioxide that could be produced when (i) 1 mole of carbon is burnt in air.
  7. Ex 1.4(ii)
    Calculate the amount of carbon dioxide that could be produced when (ii) 1 mole of carbon is burnt in 16 g16\,\text{g} of dioxygen.
  8. Ex 1.4(iii)
    Calculate the amount of carbon dioxide that could be produced when (iii) 2 moles of carbon are burnt in 16 g16\,\text{g} of dioxygen.
  9. Ex 1.5
    Calculate the mass of sodium acetate (CH3COONa)\left(\text{CH}_3\text{COONa}\right) required to make 500 mL500\,\text{mL} of 0.3750.375 molar aqueous solution. Molar mass of sodium acetate is 82.0245 g mol−182.0245\,\text{g mol}^{-1}.
  10. Ex 1.6
    Calculate the concentration of nitric acid in moles per litre in a sample which has a density, 1.41 g mL−11.41\,\text{g mL}^{-1} and the mass per cent of nitric acid in it being 69%.
  11. Ex 1.7
    How much copper can be obtained from 100 g100\,\text{g} of copper sulphate (CuSO4)\left(\text{CuSO}_4\right)?
  12. Ex 1.8
    Determine the molecular formula of an oxide of iron, in which the mass per cent of iron and oxygen are 69.9 and 30.1, respectively.
  13. Ex 1.9
    Calculate the atomic mass (average) of chlorine using the following data:
    % Natural AbundanceMolar Mass
    35Cl^{35}\text{Cl}75.7734.9689
    37Cl^{37}\text{Cl}24.2336.9659
  14. Ex 1.10(i)
    In three moles of ethane (C2H6)\left(\text{C}_2\text{H}_6\right), calculate the following: (i) Number of moles of carbon atoms.
  15. Ex 1.10(ii)
    In three moles of ethane (C2H6)\left(\text{C}_2\text{H}_6\right), calculate the following: (ii) Number of moles of hydrogen atoms.
  16. Ex 1.10(iii)
    In three moles of ethane (C2H6)\left(\text{C}_2\text{H}_6\right), calculate the following: (iii) Number of molecules of ethane.
  17. Ex 1.11
    What is the concentration of sugar (C12H22O11)\left(\text{C}_{12}\text{H}_{22}\text{O}_{11}\right) in mol L−1\text{mol L}^{-1} if its 20 g20\,\text{g} are dissolved in enough water to make a final volume up to 2 L2\,\text{L}?
  18. Ex 1.12
    If the density of methanol is 0.793 kg L−10.793\,\text{kg L}^{-1}, what is its volume needed for making 2.5 L2.5\,\text{L} of its 0.25 M0.25\,\text{M} solution?
  19. Ex 1.13
    Pressure is determined as force per unit area of the surface. The SI unit of pressure, pascal is as shown below: 1 Pa=1 N m−21\,\text{Pa} = 1\,\text{N m}^{-2} If mass of air at sea level is 1034 g cm−21034\,\text{g cm}^{-2}, calculate the pressure in pascal.
  20. Ex 1.14
    What is the SI unit of mass? How is it defined?
  21. Ex 1.15
    Match the following prefixes with their multiples:
    PrefixesMultiples
    (i)micro10610^{6}
    (ii)deca10910^{9}
    (iii)mega10−610^{-6}
    (iv)giga10−1510^{-15}
    (v)femto1010
  22. Ex 1.16
    What do you mean by significant figures?
  23. Ex 1.17(i)
    A sample of drinking water was found to be severely contaminated with chloroform, CHCl3\text{CHCl}_3, supposed to be carcinogenic in nature. The level of contamination was 15 ppm15\,\text{ppm} (by mass). (i) Express this in per cent by mass.
  24. Ex 1.17(ii)
    A sample of drinking water was found to be severely contaminated with chloroform, CHCl3\text{CHCl}_3, supposed to be carcinogenic in nature. The level of contamination was 15 ppm15\,\text{ppm} (by mass). (ii) Determine the molality of chloroform in the water sample.
  25. Ex 1.18(i)
    Express the following in the scientific notation: (i) 0.00480.0048
  26. Ex 1.18(ii)
    Express the following in the scientific notation: (ii) 234,000234{,}000
  27. Ex 1.18(iii)
    Express the following in the scientific notation: (iii) 80088008
  28. Ex 1.18(iv)
    Express the following in the scientific notation: (iv) 500.0500.0
  29. Ex 1.18(v)
    Express the following in the scientific notation: (v) 6.00126.0012
  30. Ex 1.19(i)
    How many significant figures are present in the following? (i) 0.00250.0025
  31. Ex 1.19(ii)
    How many significant figures are present in the following? (ii) 208208
  32. Ex 1.19(iii)
    How many significant figures are present in the following? (iii) 50055005
  33. Ex 1.19(iv)
    How many significant figures are present in the following? (iv) 126,000126{,}000
  34. Ex 1.19(v)
    How many significant figures are present in the following? (v) 500.0500.0
  35. Ex 1.19(vi)
    How many significant figures are present in the following? (vi) 2.00342.0034
  36. Ex 1.20(i)
    Round up the following upto three significant figures: (i) 34.21634.216
  37. Ex 1.20(ii)
    Round up the following upto three significant figures: (ii) 10.410710.4107
  38. Ex 1.20(iii)
    Round up the following upto three significant figures: (iii) 0.045970.04597
  39. Ex 1.20(iv)
    Round up the following upto three significant figures: (iv) 28082808
  40. Ex 1.21(a)
    The following data are obtained when dinitrogen and dioxygen react together to form different compounds:
    Mass of dinitrogenMass of dioxygen
    (i)14 g14\,\text{g}16 g16\,\text{g}
    (ii)14 g14\,\text{g}32 g32\,\text{g}
    (iii)28 g28\,\text{g}32 g32\,\text{g}
    (iv)28 g28\,\text{g}80 g80\,\text{g}
    (a) Which law of chemical combination is obeyed by the above experimental data? Give its statement.
  41. Ex 1.21(b)
    (b) Fill in the blanks in the following conversions: (i) 1 km=…… mm=…… pm1\,\text{km} = \ldots\ldots\,\text{mm} = \ldots\ldots\,\text{pm} (ii) 1 mg=…… kg=…… ng1\,\text{mg} = \ldots\ldots\,\text{kg} = \ldots\ldots\,\text{ng} (iii) 1 mL=…… L=…… dm31\,\text{mL} = \ldots\ldots\,\text{L} = \ldots\ldots\,\text{dm}^3
  42. Ex 1.22
    If the speed of light is 3.0×108 m s−13.0 \times 10^{8}\,\text{m s}^{-1}, calculate the distance covered by light in 2.00 ns2.00\,\text{ns}.
  43. Ex 1.23(i)
    In a reaction A+B2→AB2\text{A} + \text{B}_2 \rightarrow \text{AB}_2 Identify the limiting reagent, if any, in the following reaction mixtures. (i) 300 atoms of A + 200 molecules of B
  44. Ex 1.23(ii)
    In a reaction A+B2→AB2\text{A} + \text{B}_2 \rightarrow \text{AB}_2 Identify the limiting reagent, if any, in the following reaction mixtures. (ii) 2 mol A + 3 mol B
  45. Ex 1.23(iii)
    In a reaction A+B2→AB2\text{A} + \text{B}_2 \rightarrow \text{AB}_2 Identify the limiting reagent, if any, in the following reaction mixtures. (iii) 100 atoms of A + 100 molecules of B
  46. Ex 1.23(iv)
    In a reaction A+B2→AB2\text{A} + \text{B}_2 \rightarrow \text{AB}_2 Identify the limiting reagent, if any, in the following reaction mixtures. (iv) 5 mol A + 2.5 mol B
  47. Ex 1.23(v)
    In a reaction A+B2→AB2\text{A} + \text{B}_2 \rightarrow \text{AB}_2 Identify the limiting reagent, if any, in the following reaction mixtures. (v) 2.5 mol A + 5 mol B
  48. Ex 1.24
    Dinitrogen and dihydrogen react with each other to produce ammonia according to the following chemical equation: N2(g)+H2(g)→2NH3(g)\text{N}_2(g) + \text{H}_2(g) \rightarrow 2\text{NH}_3(g) (i) Calculate the mass of ammonia produced if 2.00×103 g2.00 \times 10^{3}\,\text{g} dinitrogen reacts with 1.00×103 g1.00 \times 10^{3}\,\text{g} of dihydrogen. (ii) Will any of the two reactants remain unreacted? (iii) If yes, which one and what would be its mass?
  49. Ex 1.25
    How are 0.50 mol0.50\,\text{mol} Na2CO3\text{Na}_2\text{CO}_3 and 0.50 M0.50\,\text{M} Na2CO3\text{Na}_2\text{CO}_3 different?
  50. Ex 1.26
    If 10 volumes of dihydrogen gas reacts with five volumes of dioxygen gas, how many volumes of water vapour would be produced?
  51. Ex 1.27(i)
    Convert the following into basic units: (i) 28.7 pm28.7\,\text{pm}
  52. Ex 1.27(ii)
    Convert the following into basic units: (ii) 15.15 pm15.15\,\text{pm}
  53. Ex 1.27(iii)
    Convert the following into basic units: (iii) 25365 mg25365\,\text{mg}
  54. Ex 1.28
    Which one of the following will have the largest number of atoms?
    1. A.
      1 g1\,\text{g} Au (s)
    2. B.
      1 g1\,\text{g} Na (s)
    3. C.
      1 g1\,\text{g} Li (s)
    4. D.
      1 g1\,\text{g} of Cl2\text{Cl}_2 (g)
  55. Ex 1.29
    Calculate the molarity of a solution of ethanol in water, in which the mole fraction of ethanol is 0.0400.040 (assume the density of water to be one).
  56. Ex 1.30
    What will be the mass of one 12C^{12}\text{C} atom in g?
  57. Ex 1.31(i)
    How many significant figures should be present in the answer of the following calculations? (i) 0.02856×298.15×0.1120.5785\dfrac{0.02856 \times 298.15 \times 0.112}{0.5785}
  58. Ex 1.31(ii)
    How many significant figures should be present in the answer of the following calculations? (ii) 5×5.3645 \times 5.364
  59. Ex 1.31(iii)
    How many significant figures should be present in the answer of the following calculations? (iii) 0.0125+0.7864+0.02150.0125 + 0.7864 + 0.0215
  60. Ex 1.32
    Use the data given in the following table to calculate the molar mass of naturally occuring *argon* isotopes:
    IsotopeIsotopic molar massAbundance
    36Ar^{36}\text{Ar}35.96755 g mol−135.96755\,\text{g mol}^{-1}0.337%
    38Ar^{38}\text{Ar}37.96272 g mol−137.96272\,\text{g mol}^{-1}0.063%
    40Ar^{40}\text{Ar}39.9624 g mol−139.9624\,\text{g mol}^{-1}99.600%
  61. Ex 1.33(i)
    Calculate the number of atoms in each of the following: (i) 5252 moles of Ar
  62. Ex 1.33(ii)
    Calculate the number of atoms in each of the following: (ii) 52 u52\,\text{u} of He
  63. Ex 1.33(iii)
    Calculate the number of atoms in each of the following: (iii) 52 g52\,\text{g} of He
  64. Ex 1.34
    A welding fuel gas contains carbon and hydrogen only. Burning a small sample of it in oxygen gives 3.38 g3.38\,\text{g} carbon dioxide, 0.690 g0.690\,\text{g} of water and no other products. A volume of 10.0 L10.0\,\text{L} (measured at STP) of this welding gas is found to weigh 11.6 g11.6\,\text{g}. Calculate (i) empirical formula, (ii) molar mass of the gas, and (iii) molecular formula.
  65. Ex 1.35
    Calcium carbonate reacts with aqueous HCl to give CaCl2\text{CaCl}_2 and CO2\text{CO}_2 according to the reaction, CaCO3(s)+2 HCl(aq)→CaCl2(aq)+CO2(g)+H2O(l)\text{CaCO}_3(s) + 2\,\text{HCl}(aq) \rightarrow \text{CaCl}_2(aq) + \text{CO}_2(g) + \text{H}_2\text{O}(l) What mass of CaCO3\text{CaCO}_3 is required to react completely with 25 mL25\,\text{mL} of 0.75 M0.75\,\text{M} HCl?
  66. Ex 1.36
    Chlorine is prepared in the laboratory by treating manganese dioxide (MnO2)\left(\text{MnO}_2\right) with aqueous hydrochloric acid according to the reaction 4 HCl(aq)+MnO2(s)→2H2O(l)+MnCl2(aq)+Cl2(g)4\,\text{HCl}(aq) + \text{MnO}_2(s) \rightarrow 2\text{H}_2\text{O}(l) + \text{MnCl}_2(aq) + \text{Cl}_2(g) How many grams of HCl react with 5.0 g5.0\,\text{g} of manganese dioxide?