Chemistry · Textbook solutions

Introduction to Analytical Chemistry

Every solved example, exercise, and miscellaneous question — in the order the textbook teaches them. · 67 questions

2. Introduction to Analytical Chemistry — worked examples

18 q

Solved Problems 2.1 – 2.18

Worked · 18
  1. Solved Ex.2.1
    Add 5.55×1045.55 \times 10^4 and 6.95×1036.95 \times 10^3, expressing the result in scientific notation.
  2. Solved Ex.2.2
    Perform the subtraction 3.5×10−2−5.8×10−33.5 \times 10^{-2} - 5.8 \times 10^{-3}, expressing the result in scientific notation.
  3. Solved Ex.2.3
    Evaluate (5.6×105)×(6.9×108)(5.6 \times 10^5) \times (6.9 \times 10^8), expressing the result in scientific notation.
  4. Solved Ex.2.4
    Evaluate (9.8×10−2)×(2.5×10−6)(9.8 \times 10^{-2}) \times (2.5 \times 10^{-6}), expressing the result in scientific notation.
  5. Solved Ex.2.5
    In laboratory experiment, 10 g potassium chlorate sample on decomposition gives following data ; The sample contains 3.8 g of oxygen and the actual mass of oxygen in the quantity of potassium chlorate is 3.92 g. Calculate absolute error and relative error.
  6. Solved Ex.2.6
    The three identical samples of potassium chlorate are decomposed. The mass of oxygen is determined to be 3.87 g, 3.95 g and 3.89 g for the set. Calculate absolute deviation and relative deviation.
  7. Solved Ex.2.7
    How many significant figures are present in the following measurements ? a. 4.065 m b. 0.32 g c. 57.98 cm357.98\ \mathrm{cm^3} d. 0.02 s e. 4.0×10−4 km4.0 \times 10^{-4}\ \mathrm{km} f. 604.0820 kg g. 307.100×10−5 cm307.100 \times 10^{-5}\ \mathrm{cm}
  8. Solved Ex.2.8
    Round off each of the following to the number of significant digits indicated : a. 1.223 to two digits b. 12.56 to three digits c. 122.17 to four digits d. 231.5 to three digits.
  9. Solved Ex.2.9
    A compound contains 4.07 % hydrogen, 24.27% carbon and 71.65 % chlorine by mass. Its molar mass is 98.96 g. What is its empirical formula ? Atomic masses of hydrogen, carbon and chlorine are 1.008, 12.000 and 35.453 u, respectively
  10. Solved Ex.2.10
    A compound with molar mass 159 was found to contain 39.62 % copper and 20.13 % sulfur. Suggest molecular formula for the compound (Atomic masses: Cu = 63, S = 32 and O = 16).
  11. Solved Ex.2.11
    Calculate the mass of carbon dioxide and water formed on complete combustion of 24 g of methane gas. (Atomic masses, C = 12 u, H = 1 u, O = 16 u)
  12. Solved Ex.2.12
    How much CaO will be produced by decomposition of 5g CaCO3\mathrm{CaCO_3} ?
  13. Solved Ex.2.13
    How many litres of oxygen at STP are required to burn completely 2.2 g of propane, C3H8\mathrm{C_3H_8} ?
  14. Solved Ex.2.14
    A piece of zinc weighing 0.635 g when treated with excess of dilute H2SO4\mathrm{H_2SO_4} liberated 200 cm3200\ \mathrm{cm^3} of hydrogen at STP. Calculate the percentage purity of the zinc sample.
  15. Solved Ex.2.15
    Urea [(NH2)2CO][(\mathrm{NH_2})_2\mathrm{CO}] is prepared by reacting ammonia with carbon dioxide. 2 NH3(g)+CO2(g)⟶(NH2)2CO(aq)+H2O(l)2\,\mathrm{NH_3(g)} + \mathrm{CO_2(g)} \longrightarrow (\mathrm{NH_2})_2\mathrm{CO(aq)} + \mathrm{H_2O(l)} In one process, 637.2 g of NH3\mathrm{NH_3} are treated with 1142 g of CO2\mathrm{CO_2}. (a) Which of the two reactants is the limiting reagent ? (b) Calculate the mass of (NH2)2CO(\mathrm{NH_2})_2\mathrm{CO} formed. (c) How much excess reagent (in grams) is left at the end of the reaction ?
  16. Solved Ex.2.16
    A solution is prepared by adding 2 g of a substance A to 18 g of water. Calculate the mass percent of the solute.
  17. Solved Ex.2.17
    Calculate the molarity of NaOH in the solution prepared by dissolving its 4 g in enough water to form 250 mL of the solution.
  18. Solved Ex.2.18
    The density of 3M solution of NaCl is 1.25 g mL−11.25\ \mathrm{g\ mL^{-1}} Calculate molality of the solution.

Exercises

49 q

1. Choose correct option

Practice · 12
  1. Choose correct option
    Ex Q.1 (A)
    The branch of chemistry which deals with study of separation, identification, and quantitaive determination of the composition of different substances is called as .............
    1. A.
      Physical chemistry
    2. B.
      Inorganic chemistry
    3. C.
      Organic chemistry
    4. D.
      Analytical chemistry
  2. Ex Q.1 (B)
    Which one of the following property of matter is Not quantitative in nature ?
    1. A.
      Mass
    2. B.
      Length
    3. C.
      Colour
    4. D.
      Volume
  3. Ex Q.1 (C)
    SI unit of mass is ........
    1. A.
      kg
    2. B.
      mol
    3. C.
      pound
    4. D.
      m3\mathrm{m^3}
  4. Ex Q.1 (D)
    The number of significant figures in 1.50×1041.50 \times 10^4 g is ...........
    1. A.
      2
    2. B.
      3
    3. C.
      4
    4. D.
      6
  5. Ex Q.1 (E)
    In Avogadro's constant 6.022×1023 mol−16.022 \times 10^{23}\ \mathrm{mol^{-1}}, the number of significant figures is ..........
    1. A.
      3
    2. B.
      4
    3. C.
      5
    4. D.
      6
  6. Ex Q.1 (F)
    By decomposition of 25 g of CaCO3\mathrm{CaCO_3}, the amount of CaO produced will be ............
    1. A.
      2.8 g
    2. B.
      8.4 g
    3. C.
      14.0 g
    4. D.
      28.0 g
  7. Ex Q.1 (G)
    How many grams of water will be produced by complete combustion of 12 g of methane gas
    1. A.
      16
    2. B.
      27
    3. C.
      36
    4. D.
      56
  8. Ex Q.1 (H)
    Two elements A (At. mass 75) and B (At. mass 16) combine to give a compound having 75.8 % of A. The formula of the compound is
    1. A.
      AB
    2. B.
      A2B\mathrm{A_2B}
    3. C.
      AB2\mathrm{AB_2}
    4. D.
      A2B3\mathrm{A_2B_3}
  9. Ex Q.1 (I)
    The hydrocarbon contains 79.87 % carbon and 20.13 % of hydrogen. What is its empirical formula ?
    1. A.
      CH
    2. B.
      CH2\mathrm{CH_2}
    3. C.
      CH3\mathrm{CH_3}
    4. D.
      C2H5\mathrm{C_2H_5}
  10. Ex Q.1 (J)
    How many grams of oxygen will be required to react completely with 27 g of Al? (Atomic mass : Al = 27, O = 16)
    1. A.
      8
    2. B.
      16
    3. C.
      24
    4. D.
      32
  11. Ex Q.1 (K)
    In CuSO4⋅5H2O\mathrm{CuSO_4 \cdot 5H_2O} the percentage of water is ...... (Cu = 63.5, S = 32, O = 16, H = 1)
    1. A.
      10 %
    2. B.
      36 %
    3. C.
      60 %
    4. D.
      72 %
  12. Ex Q.1 (L)
    When two properties of a system are mathematically related to each other, the relation can be deduced by
    1. A.
      Working out mean deviation
    2. B.
      Plotting a graph
    3. C.
      Calculating relative error
    4. D.
      all the above three

2. Answer the following questions

Practice · 11
  1. Answer the following questions
    Ex Q.2 (A)
    Define : Least count
  2. Ex Q.2 (B)
    What do you mean by significant figures? State the rules for deciding significant figures.
  3. Ex Q.2 (C)
    Distinguish between accuracy and precision.
  4. Ex Q.2 (D)
    Explain the terms percentage composition, empirical formula and molecular formula.
  5. Ex Q.2 (E)
    What is a limiting reagent ? Explain.
  6. Ex Q.2 (F)
    What do you mean by SI units ? What is the SI unit of mass ?
  7. Ex Q.2 (G)
    Explain the following terms (a) Mole fraction (b) Molarity (c) Molality
  8. Ex Q.2 (H)
    Define : Stoichiometry
  9. Ex Q.2 (I)
    Why there is a need of rounding off figures during calculation ?
  10. Ex Q.2 (J)
    Why does molarity of a solution depend upon temperature ?
  11. Ex Q.2 (M)
    Define Analytical chemistry. Why is accurate measurement crucial in science?

3. Solve the following questions

Practice · 4
  1. Solve the following questions
    Ex Q.3 (A)
    How many significant figures are in each of the following quantities ? a. 45.26 ft b. 0.109 in c. 0.00025 kg d. 2.3659×10−8 cm2.3659 \times 10^{-8}\ \mathrm{cm} e. 52.0 cm352.0\ \mathrm{cm^3} f. 0.00020 kg g. 8.50×104 mm8.50 \times 10^4\ \mathrm{mm} h. 300.0 cg
  2. Ex Q.3 (B)
    Round off each of the following quantities to two significant figures : a. 25.55 mL b. 0.00254 m c. 1.491×105 mg1.491 \times 10^5\ \mathrm{mg} d. 199 g
  3. Ex Q.3 (C)
    Round off each of the following quantities to three significant figures : a. 1.43 cm31.43\ \mathrm{cm^3} b. 458×102 cm458 \times 10^2\ \mathrm{cm} c. 643 cm2643\ \mathrm{cm^2} d. 0.039 m e. 6.398×10−3 km6.398 \times 10^{-3}\ \mathrm{km} f. 0.0179 g g. 79,000 m h. 42,150 i. 649.85; j. 23,642,000 mm k. 0.0041962 kg
  4. Ex Q.3 (D)
    Express the following sum to appropriate number of significant figures : a. 2.3×103 mL+4.22×104 mL+9.04×103 mL+8.71×105 mL2.3 \times 10^3\ \mathrm{mL} + 4.22 \times 10^4\ \mathrm{mL} + 9.04 \times 10^3\ \mathrm{mL} + 8.71 \times 10^5\ \mathrm{mL}; b. 319.5 g−20460 g−0.0639 g−45.642 g−4.173 g319.5\ \mathrm{g} - 20460\ \mathrm{g} - 0.0639\ \mathrm{g} - 45.642\ \mathrm{g} - 4.173\ \mathrm{g}

4. Solve the following problems

Practice · 22
  1. Solve the following problems
    Ex Q.4 (A)
    Express the following quantities in exponential terms. a. 0.0003498 b. 235.4678 c. 70000.0 d. 1569.00
  2. Ex Q.4 (B)
    Give the number of significant figures in each of the following a. 1.230×1041.230 \times 10^4 b. 0.002030 c. 1.23×1041.23 \times 10^4 d. 1.89×10−41.89 \times 10^{-4}
  3. Ex Q.4 (C)
    Express the quantities in above (B) with or without exponents as the case may be. [The quantities of (B) are : a. 1.230×1041.230 \times 10^4, b. 0.002030, c. 1.23×1041.23 \times 10^4, d. 1.89×10−41.89 \times 10^{-4}]
  4. Ex Q.4 (D)
    Find out the molar masses of the following compounds : a. Copper sulphate crystal (CuSO4⋅5H2O)(\mathrm{CuSO_4 \cdot 5H_2O}) b. Sodium carbonate, decahydrate (Na2CO3⋅10H2O)(\mathrm{Na_2CO_3 \cdot 10H_2O}) c. Mohr's salt [FeSO4(NH4)2SO4⋅6H2O][\mathrm{FeSO_4(NH_4)_2SO_4 \cdot 6H_2O}] (At. mass : Cu = 63.5; S = 32; O = 16; H = 1; Na = 23; C = 12; Fe = 56; N = 14)
  5. Ex Q.4 (E)
    Work out the percentage composition of constituents elements in the following compounds : a. Lead phosphate [Pb3(PO4)2][\mathrm{Pb_3(PO_4)_2}], b. Potassium dichromate (K2Cr2O7)(\mathrm{K_2Cr_2O_7}), c. Macrocosmic salt - Sodium ammonium hydrogen phosphate, tetrahydrate (NaNH4HPO4⋅4H2O)(\mathrm{NaNH_4HPO_4 \cdot 4H_2O}) (At. mass : Pb = 207; P = 31; O = 16; K = 39; Cr = 52; Na = 23; N = 14)
  6. Ex Q.4 (F)
    Find the percentage composition of constituent green vitriol crystals (FeSO4⋅7H2O)(\mathrm{FeSO_4 \cdot 7H_2O}). Also find out the mass of iron and the water of crystallisation in 4.54 kg of the crystals. (At. mass : Fe = 56; S = 32; O = 16)
  7. Ex Q.4 (G)
    The red colour of blood is due to a compound called "haemoglobin". It contains 0.335 % of iron. Four atoms of iron are present in one molecule of haemoglobin. What is its molecular weight ? (At. mass : Fe 55.84)
  8. Ex Q.4 (H)
    A substance, on analysis, gave the following percent composition: Na = 43.4 %, C = 11.3 % and O = 45.3 %. Calculate the empirical formula. (At. mass Na = 23 u, C = 12 u, O = 16 u).
  9. Ex Q.4 (I)
    Assuming the atomic weight of a metal M to be 56, find the empirical formula of its oxide containing 70.0% of M.
  10. Ex Q.4 (J)
    1.00 g of a hydrated salt contains 0.2014 g of iron, 0.1153 g of sulfur, 0.2301 g of oxygen and 0.4532 g of water of crystallisation. Find the empirical formula. (At. wt. : Fe = 56; S = 32; O = 16)
  11. Ex Q.4 (K)
    An organic compound containing oxygen, carbon, hydrogen and nitrogen contains 20 % carbon, 6.7 % hydrogen and 46.67 % nitrogen. Its molecular mass was found to be 60. Find the molecular formula of the compound.
  12. Ex Q.4 (L)
    A compound on analysis gave the following percentage composition by mass : H = 9.09; O = 36.36; C = 54.55. Mol mass of compound is 88. Find its molecular formula.
  13. Ex Q.4 (M)
    Carbohydrates are compounds containing only carbon, hydrogen and oxygen. When heated in the absence of air, these compounds decompose to form carbon and water. If 310 g of a carbohydrate leave a residue of 124 g of carbon on heating in absence of air, what is the empirical formula of the carbohydrate ?
  14. Ex Q.4 (N)
    Write each of the following in exponential notation : a. 3,672,199 b. 0.000098 c. 0.00461 d. 198.75
  15. Ex Q.4 (O)
    Write each of the following numbers in ordinary decimal form : a. 3.49×10−113.49 \times 10^{-11} b. 3.75×10−13.75 \times 10^{-1} c. 5.16×1045.16 \times 10^4 d. 43.71×10−443.71 \times 10^{-4} e. 0.011×10−30.011 \times 10^{-3} f. 14.3×10−214.3 \times 10^{-2} g. 0.00477×1050.00477 \times 10^5 h. 5.00858585
  16. Ex Q.4 (P)
    Perform each of the following calculations. Round off your answers to two digits. a. 13.40×1024\dfrac{1}{3.40 \times 10^{24}}; b. 339.00×10−4\dfrac{33}{9.00 \times 10^{-4}}; c. 1.4×109(2.77×103)(3.76×105)\dfrac{1.4 \times 10^9}{(2.77 \times 10^3)(3.76 \times 10^5)}; d. (4×10−3)(9.9×10−7)(789)(1.002×10−10)(0.3×102)\dfrac{(4 \times 10^{-3})(9.9 \times 10^{-7})}{(789)(1.002 \times 10^{-10})(0.3 \times 10^2)}
  17. Ex Q.4 (Q)
    Perform each of the following calculations. Round off your answers to three digits. a. (3.26 104)(1.54 106)(3.26\ 104)(1.54\ 106) b. (8.39 107)(4.53 109)(8.39\ 107)(4.53\ 109) c. 8.94×1064.35×104\dfrac{8.94 \times 10^6}{4.35 \times 10^4} d. (9.28×109)(9.9×10−7)(511)(2.98×10−6)\dfrac{(9.28 \times 10^9)(9.9 \times 10^{-7})}{(511)(2.98 \times 10^{-6})}
  18. Ex Q.4 (R)
    Perform the following operations : a. 3.971×107+1.98×1043.971 \times 10^7 + 1.98 \times 10^4; b. 1.05×10−4−9.7×10−51.05 \times 10^{-4} - 9.7 \times 10^{-5}; c. 4.11×10−3+8.1 10−44.11 \times 10^{-3} + 8.1\ 10^{-4}; d. 2.12×106−3.5×1052.12 \times 10^6 - 3.5 \times 10^5.
  19. Ex Q.4 (S)
    A 1.000 mL sample of acetone, a common solvent used as a paint remover, was placed in a small bottle whose mass was known to be 38.0015 g. The following values were obtained when the acetone - filled bottle was weighed : 38.7798 g, 38.7795 g and 38.7801 g. How would you characterise the precision and accuracy of these measurements if the actual mass of the acetone was 0.7791 g ?
  20. Ex Q.4 (T)
    Your laboratory partner was given the task of measuring the length of a box (approx 5 in) as accurately as possible, using a metre stick graduated in milimeters. He supplied you with the following measurements: 12.65 cm, 12.6 cm, 12.65 cm, 12.655 cm, 126.55 mm, 12 cm. a. State which of the measurements you would accept, giving the reason. b. Give your reason for rejecting each of the others.
  21. Ex Q.4 (U)
    What weight of calcium oxide will be formed on heating 19.3 g of calcium carbonate ? (At. wt. : Ca = 40; C = 12; O = 16)
  22. Ex Q.4 (V)
    The hourly energy requirements of an astronaut can be satisfied by the energy released when 34 grams of sucrose are "burnt" in his body. How many grams of oxygen would be needed to be carried in space capsule to meet his requirement for one day ?