CALCULATIONS IN ANALYTICAL BIOCHEMISTRY

The following are top 100 calculations questions and answers in analytical biochemistry that will foster a better understanding of the concept of this course-analytical Biochemistry:

 

1. Q: Calculate the molarity of a solution containing 0.25 moles of glucose dissolved in 500 mL of water.

   A: Molarity (M) = moles of solute / volume of solution in liters

      M = 0.25 moles / 0.5 L = 0.5 M

 

2. Q: What is the dilution factor when 5 mL of a 0.1 M solution is diluted to a final volume of 50 mL?

   A: Dilution factor = final volume / initial volume

      Dilution factor = 50 mL / 5 mL = 10

 

3. Q: Calculate the absorbance of a sample with a transmittance of 80%.

   A: Absorbance (A) = -log10(T), where T is the transmittance

      A = -log10(0.80) ≈ 0.0969

 

4. Q: A protein solution has an absorbance of 0.5 at a given wavelength. Calculate the molar absorptivity (ε) if the concentration of the protein is 0.1 M.

   A: Absorbance (A) = ε * concentration (c) * path length (l)

      ε = A / (c * l) = 0.5 / (0.1 M * 1 cm) = 5 L·mol⁻¹·cm⁻¹

 

5. Q: What is the molecular weight of a peptide composed of amino acids with the following masses: 129.2, 146.2, 115.1, 131.3, and 147.1 Da?

   A: Molecular weight = sum of the masses of individual amino acids

      Molecular weight = 129.2 + 146.2 + 115.1 + 131.3 + 147.1 = 669.9 Da

 

6. Q: Calculate the percentage composition of a compound with the following elemental masses: C = 12 g/mol, H = 1 g/mol, O = 16 g/mol.

   A: Percentage composition of carbon = (12 g/mol / 29 g/mol) * 100 ≈ 41.38%

      Percentage composition of hydrogen = (1 g/mol / 29 g/mol) * 100 ≈ 3.45%

      Percentage composition of oxygen = (16 g/mol / 29 g/mol) * 100 ≈ 55.17%

 

7. Q: How many moles of NaCl are present in 100 g of a 5% (w/w) NaCl solution?

   A: Mass of NaCl = 5% of 100 g = 5 g

      Moles of NaCl = mass / molar mass = 5 g / 58.44 g/mol ≈ 0.0856 mol

 

8. Q: Calculate the pKa of an acid if the concentration of the acid and its conjugate base are 0.01 M and 0.1 M, respectively, and the pH of the solution is 5.

   A: pH = pKa + log([A-]/[HA])

      5 = pKa + log(0.1/0.01)

      pKa = 5 - log(10) = 4

 

9. Q: Calculate the enzymatic activity of an enzyme that catalyzes the conversion of 100 μmol of substrate per minute.

   A: Enzymatic activity = amount of substrate converted per unit time

      Enzymatic activity = 100 μmol/min

 

10. Q: What is the turnover number of an enzyme if it converts 1,000 moles of substrate per minute, and the enzyme concentration is 0.01 M?

    A: Turnover number (kcat) = enzymatic activity / enzyme concentration

       kcat = 1000 moles/min / 0.01 M = 100,000 min⁻¹

 

11. Q: Calculate the specific activity of an enzyme with an enzymatic activity of 200 units and a protein concentration of 2 mg/mL.

    A: Specific activity = enzymatic activity / protein concentration

       Specific activity = 200 units / 2 mg/mL = 100 units/mg

 

12. Q: A 50 mL solution contains 0.1 moles of solute. What is the molarity of the solution?

    A: Molarity (M) = moles of solute / volume of solution in liters

       M = 0.1 moles / 0.05 L = 2 M

 

13. Q: If a reaction has a rate constant of 0.02 s⁻¹, what is its half-life?

    A: Half-life (t1/2) = ln(2) / rate constant

       t1/2 = ln(2) / 0.02 s⁻¹ ≈ 34.65 seconds

 

14. Q: A buffer contains 0.1 M acetic acid (pKa = 4.76) and 0.2 M sodium acetate. Calculate the pH of the buffer.

    A: pH = pKa + log([A-]/[HA])

       pH = 4.76 + log(0.2/0.1) ≈ 4.76 + 0.301 ≈ 5.06

 

15. Q: What is the concentration of a solution if 25 mL of a 0.2 M solution is diluted to 100 mL?

    A: Concentration of diluted solution = (initial concentration * initial volume) / final volume

       Concentration = (0.2 M * 25 mL) / 100 mL = 0.05 M

 

16. Q: Calculate the absorbance of a solution with a concentration of 0.05 M and a molar absorptivity of 500 L·mol⁻¹·cm⁻¹ at a given wavelength and path length of 1 cm.

    A: Absorbance (A) = ε * concentration (c) * path length (l)

       A = 500 L·mol⁻¹·cm⁻¹ * 0.05 M * 1 cm = 25

 

17. Q: A protein solution has an absorbance of 0.7 at 280 nm. Calculate the protein concentration if the molar absorpt

 

ivity (ε) is 0.6 L·mol⁻¹·cm⁻¹.

    A: Concentration (c) = Absorbance (A) / (ε * path length)

       c = 0.7 / (0.6 L·mol⁻¹·cm⁻¹ * 1 cm) ≈ 1.17 M

 

18. Q: A peptide has a sequence of "ALADL" with molecular masses of 71.1, 65.0, 81.0, 75.1, and 71.1 Da for each amino acid, respectively. Calculate the molecular weight of the peptide.

    A: Molecular weight = sum of the masses of individual amino acids

       Molecular weight = 71.1 + 65.0 + 81.0 + 75.1 + 71.1 = 363.3 Da

 

19. Q: How many moles of glucose are present in 250 g of a 10% (w/w) glucose solution?

    A: Mass of glucose = 10% of 250 g = 0.10 * 250 g = 25 g

       Moles of glucose = mass / molar mass = 25 g / 180.16 g/mol ≈ 0.1388 mol

 

20. Q: Calculate the percentage composition of a compound with the following elemental masses: C = 40 g/mol, H = 6 g/mol, O = 16 g/mol.

    A: Percentage composition of carbon = (40 g/mol / 62 g/mol) * 100 ≈ 64.52%

       Percentage composition of hydrogen = (6 g/mol / 62 g/mol) * 100 ≈ 9.68%

       Percentage composition of oxygen = (16 g/mol / 62 g/mol) * 100 ≈ 25.81%

 

21. Q: What is the molecular weight of a DNA molecule with 2,500 base pairs, assuming an average molecular weight of 660 Da per base pair?

    A: Molecular weight = number of base pairs * average molecular weight per base pair

       Molecular weight = 2,500 base pairs * 660 Da/base pair = 1,650,000 Da

 

22. Q: How many moles of NaCl are present in 500 mL of a 0.2 M NaCl solution?

    A: Moles of NaCl = molarity * volume in liters

       Moles of NaCl = 0.2 M * 0.5 L = 0.1 moles

 

23. Q: If a reaction follows first-order kinetics with a rate constant of 0.005 s⁻¹, what is the rate of the reaction when the concentration of the reactant is 0.1 M?

    A: Rate = rate constant * concentration of reactant

       Rate = 0.005 s⁻¹ * 0.1 M = 0.0005 M/s

 

24. Q: A buffer contains 0.1 M acetic acid (pKa = 4.76) and 0.2 M sodium acetate. Calculate the concentration of the conjugate base (acetate ion) in the buffer.

    A: [A-] = [HA] * 10^(pH - pKa)

       [A-] = 0.2 M * 10^(5 - 4.76) ≈ 0.2 M * 2.29 ≈ 0.458 M

 

25. Q: Calculate the specific activity of an enzyme with an enzymatic activity of 400 units and a protein concentration of 0.05 mg/mL.

    A: Specific activity = enzymatic activity / protein concentration

       Specific activity = 400 units / 0.05 mg/mL = 8,000 units/mg

 

26. Q: How many moles of sucrose are present in 1 liter of a 0.1 M sucrose solution?

    A: Moles of sucrose = molarity * volume in liters

       Moles of sucrose = 0.1 M * 1 L = 0.1 moles

 

27. Q: Calculate the rate constant (k) for a second-order reaction with a rate of 0.01 M/s when the initial concentration of the reactant is 0.2 M.

    A: Rate = k * [A]^2

       k = Rate / [A]^2 = 0.01 M/s / (0.2 M)^2 = 0.25 M⁻¹·s⁻¹

 

28. Q: A buffer solution has a pH of 7.2 and contains 0.1 M acetic acid (pKa = 4.76) and 0.2 M sodium acetate. Calculate the ratio of [A-] to [HA] in the buffer.

    A: [A-] / [HA] = 10^(pH - pKa)

       [A-] / [HA] = 10^(7.2 - 4.76) ≈ 10² ≈ 100

 

29. Q: How many moles of HCl are present in 250 mL of a 1 M HCl solution?

    A: Moles of HCl = molarity * volume in liters

       Moles of HCl = 1 M * 0.25 L = 0.25 moles

 

30. Q: Calculate the enzymatic activity of an enzyme that converts 0.02 moles of substrate per minute.

    A: Enzymatic activity = amount of substrate converted per unit time

       Enzymatic activity = 0.02 moles/min

 

31. Q: What is the concentration of a solution if 100 mL of a 0.5 M solution is diluted to 500 mL?

    A: Concentration of diluted solution = (initial concentration * initial volume) / final volume

       Concentration = (0.5 M * 100 mL) / 500 mL = 0.1 M

 

32. Q: A protein solution has an absorbance of 0.6 at a given wavelength. Calculate the protein concentration if the molar absorptivity (ε) is 0.7 L·mol⁻¹·cm⁻¹.

    A: Concentration (c) = Absorbance (A) / (ε * path length)

       c = 0.6 / (0.7 L·mol⁻¹·cm⁻¹ * 1 cm) ≈ 0.857 M

 

33. Q: A peptide has a sequence of "GLYLYSALA" with molecular masses of 57.1, 128.2, 71.1, 146.2, 57.1, 115.1, and 57.1 Da for each amino acid, respectively. Calculate the molecular weight of the peptide.

    A: Molecular weight = sum of the masses of individual amino acids

       Molecular weight = 57.1 + 128.2 + 71.1 + 146.2 + 57.1 + 115.1 + 57.1 = 632.9 Da

 

34. Q: How many moles of NaCl are present in

 

 200 mL of a 0.2 M NaCl solution?

    A: Moles of NaCl = molarity * volume in liters

       Moles of NaCl = 0.2 M * 0.2 L = 0.04 moles

 

35. Q: If a reaction follows first-order kinetics with a rate constant of 0.01 s⁻¹, what is the half-life of the reaction?

    A: Half-life (t1/2) = ln(2) / rate constant

       t1/2 = ln(2) / 0.01 s⁻¹ ≈ 69.31 seconds

 

36. Q: A buffer contains 0.2 M acetic acid (pKa = 4.76) and 0.4 M sodium acetate. Calculate the pH of the buffer.

    A: pH = pKa + log([A-]/[HA])

       pH = 4.76 + log(0.4/0.2) ≈ 4.76 + 0.301 ≈ 5.06

 

37. Q: Calculate the specific activity of an enzyme with an enzymatic activity of 300 units and a protein concentration of 0.1 mg/mL.

    A: Specific activity = enzymatic activity / protein concentration

       Specific activity = 300 units / 0.1 mg/mL = 3,000 units/mg

 

38. Q: How many moles of glucose are present in 500 mL of a 0.2 M glucose solution?

    A: Moles of glucose = molarity * volume in liters

       Moles of glucose = 0.2 M * 0.5 L = 0.1 moles

 

39. Q: Calculate the rate constant (k) for a first-order reaction with a rate of 0.05 M/s when the initial concentration of the reactant is 0.1 M.

    A: Rate = k * [A]

       k = Rate / [A] = 0.05 M/s / 0.1 M = 0.5 s⁻¹

 

40. Q: A buffer solution has a pH of 7.0 and contains 0.2 M acetic acid (pKa = 4.76) and 0.4 M sodium acetate. Calculate the ratio of [A-] to [HA] in the buffer.

    A: [A-] / [HA] = 10^(pH - pKa)

       [A-] / [HA] = 10^(7.0 - 4.76) ≈ 10² ≈ 100

 

41. Q: How many moles of HCl are present in 100 mL of a 1 M HCl solution?

    A: Moles of HCl = molarity * volume in liters

       Moles of HCl = 1 M * 0.1 L = 0.1 moles

 

42. Q: Calculate the enzymatic activity of an enzyme that converts 0.05 moles of substrate per minute.

    A: Enzymatic activity = amount of substrate converted per unit time

       Enzymatic activity = 0.05 moles/min

 

43. Q: What is the concentration of a solution if 200 mL of a 0.5 M solution is diluted to 1 liter?

    A: Concentration of diluted solution = (initial concentration * initial volume) / final volume

       Concentration = (0.5 M * 200 mL) / 1000 mL = 0.1 M

 

44. Q: A protein solution has an absorbance of 0.8 at a given wavelength. Calculate the protein concentration if the molar absorptivity (ε) is 0.8 L·mol⁻¹·cm⁻¹.

    A: Concentration (c) = Absorbance (A) / (ε * path length)

       c = 0.8 / (0.8 L·mol⁻¹·cm⁻¹ * 1 cm) ≈ 1 M

 

45. Q: A peptide has a sequence of "ARGILELYS" with molecular masses of 156.2, 71.1, 128.2, 57.1, 115.1, and 128.2 Da for each amino acid, respectively. Calculate the molecular weight of the peptide.

    A: Molecular weight = sum of the masses of individual amino acids

       Molecular weight = 156.2 + 71.1 + 128.2 + 57.1 + 115.1 + 128.2 = 655.9 Da

 

46. Q: How many moles of NaCl are present in 150 mL of a 0.1 M NaCl solution?

    A: Moles of NaCl = molarity * volume in liters

       Moles of NaCl = 0.1 M * 0.15 L = 0.015 moles

 

47. Q: If a reaction follows first-order kinetics with a rate constant of 0.02 s⁻¹, what is the half-life of the reaction?

    A: Half-life (t1/2) = ln(2) / rate constant

       t1/2 = ln(2) / 0.02 s⁻¹ ≈ 34.65 seconds

 

48. Q: A buffer contains 0.1 M acetic acid (pKa = 4.76) and 0.2 M sodium acetate. Calculate the pH of the buffer.

    A: pH = pKa + log([A-]/[HA])

       pH = 4.76 + log(0.2/0.1) ≈ 4.76 + 0.301 ≈ 5.06

 

49. Q: Calculate the specific activity of an enzyme with an enzymatic activity of 500 units and a protein concentration of 0.05 mg/mL.

    A: Specific activity = enzymatic activity / protein concentration

       Specific activity = 500 units / 0.05 mg/mL = 10,000 units/mg

 

50. Q: How many moles of sucrose are present in 500 mL of a 0.2 M sucrose solution?

    A: Moles of sucrose = molarity * volume in liters

       Moles of sucrose = 0.2 M * 0.5 L = 0.1 moles

 

51. Q: Calculate the rate constant (k) for a second-order reaction with a rate of 0.01 M/s when the initial concentration of the reactant is 0.2 M.

    A: Rate = k * [A]^2

       k = Rate / [A]^2 = 0.01 M/s / (0.2 M)^2 = 0.25 M⁻¹·s⁻¹

 

52. Q: A buffer solution has a pH of 7.2 and contains 0.1 M acetic acid (pKa = 4.76) and 0.2 M sodium acetate. Calculate the ratio of [A-] to [HA] in the buffer.

    A: [A-] / [HA] = 10^(pH

 

 - pKa)

       [A-] / [HA] = 10^(7.2 - 4.76) ≈ 10² ≈ 100

 

53. Q: How many moles of HCl are present in 250 mL of a 1 M HCl solution?

    A: Moles of HCl = molarity * volume in liters

       Moles of HCl = 1 M * 0.25 L = 0.25 moles

 

54. Q: Calculate the enzymatic activity of an enzyme that converts 0.02 moles of substrate per minute.

    A: Enzymatic activity = amount of substrate converted per unit time

       Enzymatic activity = 0.02 moles/min

 

55. Q: What is the concentration of a solution if 50 mL of a 0.2 M solution is diluted to 200 mL?

    A: Concentration of diluted solution = (initial concentration * initial volume) / final volume

       Concentration = (0.2 M * 50 mL) / 200 mL = 0.05 M

 

56. Q: A protein solution has an absorbance of 0.5 at a given wavelength. Calculate the protein concentration if the molar absorptivity (ε) is 0.5 L·mol⁻¹·cm⁻¹.

    A: Concentration (c) = Absorbance (A) / (ε * path length)

       c = 0.5 / (0.5 L·mol⁻¹·cm⁻¹ * 1 cm) ≈ 1 M

 

57. Q: A peptide has a sequence of "LYSARGILE" with molecular masses of 128.2, 156.2, 71.1, 128.2, 57.1, 115.1, and 128.2 Da for each amino acid, respectively. Calculate the molecular weight of the peptide.

    A: Molecular weight = sum of the masses of individual amino acids

       Molecular weight = 128.2 + 156.2 + 71.1 + 128.2 + 57.1 + 115.1 + 128.2 = 784.1 Da

 

58. Q: How many moles of NaCl are present in 100 mL of a 0.2 M NaCl solution?

    A: Moles of NaCl = molarity * volume in liters

       Moles of NaCl = 0.2 M * 0.1 L = 0.02 moles

 

59. Q: If a reaction follows first-order kinetics with a rate constant of 0.03 s⁻¹, what is the half-life of the reaction?

    A: Half-life (t1/2) = ln(2) / rate constant

       t1/2 = ln(2) / 0.03 s⁻¹ ≈ 23.10 seconds

 

60. Q: A buffer contains 0.2 M acetic acid (pKa = 4.76) and 0.4 M sodium acetate. Calculate the pH of the buffer.

    A: pH = pKa + log([A-]/[HA])

       pH = 4.76 + log(0.4/0.2) ≈ 4.76 + 0.301 ≈ 5.06

 

61. Q: Calculate the specific activity of an enzyme with an enzymatic activity of 200 units and a protein concentration of 0.1 mg/mL.

    A: Specific activity = enzymatic activity / protein concentration

       Specific activity = 200 units / 0.1 mg/mL = 2,000 units/mg

 

62. Q: How many moles of glucose are present in 100 mL of a 0.2 M glucose solution?

    A: Moles of glucose = molarity * volume in liters

       Moles of glucose = 0.2 M * 0.1 L = 0.02 moles

 

63. Q: Calculate the rate constant (k) for a first-order reaction with a rate of 0.02 M/s when the initial concentration of the reactant is 0.1 M.

    A: Rate = k * [A]

       k = Rate / [A] = 0.02 M/s / 0.1 M = 0.2 s⁻¹

 

64. Q: A buffer solution has a pH of 7.0 and contains 0.2 M acetic acid (pKa = 4.76) and 0.4 M sodium acetate. Calculate the ratio of [A-] to [HA] in the buffer.

    A: [A-] / [HA] = 10^(pH - pKa)

       [A-] / [HA] = 10^(7.0 - 4.76) ≈ 10² ≈ 100

 

65. Q: How many moles of HCl are present in 50 mL of a 1 M HCl solution?

    A: Moles of HCl = molarity * volume in liters

       Moles of HCl = 1 M * 0.05 L = 0.05 moles

 

66. Q: Calculate the enzymatic activity of an enzyme that converts 0.01 moles of substrate per minute.

    A: Enzymatic activity = amount of substrate converted per unit time

       Enzymatic activity = 0.01 moles/min

 

67. Q: What is the concentration of a solution if 150 mL of a 0.2 M solution is diluted to 500 mL?

    A: Concentration of diluted solution = (initial concentration * initial volume) / final volume

       Concentration = (0.2 M * 150 mL) / 500 mL = 0.06 M

 

68. Q: A protein solution has an absorbance of 0.3 at a given wavelength. Calculate the protein concentration if the molar absorptivity (ε) is 0.4 L·mol⁻¹·cm⁻¹.

    A: Concentration (c) = Absorbance (A) / (ε * path length)

       c = 0.3 / (0.4 L·mol⁻¹·cm⁻¹ * 1 cm) ≈ 0.75 M

 

69. Q: A peptide has a sequence of "ILEVALARG" with molecular masses of 71.1, 99.1, 128.2, 99.1, 71.1, 115.1, and 57.1 Da for each amino acid, respectively. Calculate the molecular weight of the peptide.

    A: Molecular weight = sum of the masses of individual amino acids

       Molecular weight = 71.1 + 99.1 + 128.2 + 99.1 + 71.1 + 115.1 + 57.1 = 640.8 Da

 

70. Q: How many moles of NaCl are present in 50 mL of a 0.2 M NaCl solution?

    A: Moles of NaCl = molarity * volume in liters

       Moles of NaCl = 0.2 M

 

 * 0.05 L = 0.01 moles

 

71. Q: If a reaction follows first-order kinetics with a rate constant of 0.04 s⁻¹, what is the half-life of the reaction?

    A: Half-life (t1/2) = ln(2) / rate constant

       t1/2 = ln(2) / 0.04 s⁻¹ ≈ 17.33 seconds

 

72. Q: A buffer contains 0.2 M acetic acid (pKa = 4.76) and 0.4 M sodium acetate. Calculate the pH of the buffer.

    A: pH = pKa + log([A-]/[HA])

       pH = 4.76 + log(0.4/0.2) ≈ 4.76 + 0.301 ≈ 5.06

 

73. Q: Calculate the specific activity of an enzyme with an enzymatic activity of 300 units and a protein concentration of 0.1 mg/mL.

    A: Specific activity = enzymatic activity / protein concentration

       Specific activity = 300 units / 0.1 mg/mL = 3,000 units/mg

 

74. Q: How many moles of glucose are present in 50 mL of a 0.2 M glucose solution?

    A: Moles of glucose = molarity * volume in liters

       Moles of glucose = 0.2 M * 0.05 L = 0.01 moles

 

75. Q: Calculate the rate constant (k) for a first-order reaction with a rate of 0.01 M/s when the initial concentration of the reactant is 0.2 M.

    A: Rate = k * [A]

       k = Rate / [A] = 0.01 M/s / 0.2 M = 0.05 s⁻¹

 

76. Q: A buffer solution has a pH of 7.0 and contains 0.2 M acetic acid (pKa = 4.76) and 0.4 M sodium acetate. Calculate the ratio of [A-] to [HA] in the buffer.

    A: [A-] / [HA] = 10^(pH - pKa)

       [A-] / [HA] = 10^(7.0 - 4.76) ≈ 10² ≈ 100

 

77. Q: How many moles of HCl are present in 25 mL of a 1 M HCl solution?

    A: Moles of HCl = molarity * volume in liters

       Moles of HCl = 1 M * 0.025 L = 0.025 moles

 

78. Q: Calculate the enzymatic activity of an enzyme that converts 0.005 moles of substrate per minute.

    A: Enzymatic activity = amount of substrate converted per unit time

       Enzymatic activity = 0.005 moles/min

 

79. Q: What is the concentration of a solution if 75 mL of a 0.2 M solution is diluted to 250 mL?

    A: Concentration of diluted solution = (initial concentration * initial volume) / final volume

       Concentration = (0.2 M * 75 mL) / 250 mL = 0.06 M

 

80. Q: A protein solution has an absorbance of 0.4 at a given wavelength. Calculate the protein concentration if the molar absorptivity (ε) is 0.6 L·mol⁻¹·cm⁻¹.

    A: Concentration (c) = Absorbance (A) / (ε * path length)

       c = 0.4 / (0.6 L·mol⁻¹·cm⁻¹ * 1 cm) ≈ 0.67 M

 

81. Q: A peptide has a sequence of "SERLYSALA" with molecular masses of 87.1, 128.2, 71.1, 115.1, and 71.1 Da for each amino acid, respectively. Calculate the molecular weight of the peptide.

    A: Molecular weight = sum of the masses of individual amino acids

       Molecular weight = 87.1 + 128.2 + 71.1 + 115.1 + 71.1 = 472.6 Da

 

82. Q: How many moles of NaCl are present in 25 mL of a 0.2 M NaCl solution?

    A: Moles of NaCl = molarity * volume in liters

       Moles of NaCl = 0.2 M * 0.025 L = 0.005 moles

 

83. Q: If a reaction follows first-order kinetics with a rate constant of 0.05 s⁻¹, what is the half-life of the reaction?

    A: Half-life (t1/2) = ln(2) / rate constant

       t1/2 = ln(2) / 0.05 s⁻¹ ≈ 13.86 seconds

 

84. Q: A buffer contains 0.2 M acetic acid (pKa = 4.76) and 0.4 M sodium acetate. Calculate the pH of the buffer.

    A: pH = pKa + log([A-]/[HA])

       pH = 4.76 + log(0.4/0.2) ≈ 4.76 + 0.301 ≈ 5.06

 

85. Q: Calculate the specific activity of an enzyme with an enzymatic activity of 100 units and a protein concentration of 0.1 mg/mL.

    A: Specific activity = enzymatic activity / protein concentration

       Specific activity = 100 units / 0.1 mg/mL = 1,000 units/mg

 

86. Q: How many moles of glucose are present in 25 mL of a 0.2 M glucose solution?

    A: Moles of glucose = molarity * volume in liters

       Moles of glucose = 0.2 M * 0.025 L = 0.005 moles

 

87. Q: Calculate the rate constant (k) for a first-order reaction with a rate of 0.01 M/s when the initial concentration of the reactant is 0.1 M.

    A: Rate = k * [A]

       k = Rate / [A] = 0.01 M/s / 0.1 M = 0.1 s⁻¹

 

88. Q: A buffer solution has a pH of 7.0 and contains 0.2 M acetic acid (pKa = 4.76) and 0.4 M sodium acetate. Calculate the ratio of [A-] to [HA] in the buffer.

    A: [A-] / [HA] = 10^(pH - pKa)

       [A-] / [HA] = 10^(7.0 - 4.76) ≈ 10² ≈ 100

 

89. Q: How many moles of HCl are present in 10 mL of a 1 M HCl solution?

    A:

 

 Moles of HCl = molarity * volume in liters

       Moles of HCl = 1 M * 0.01 L = 0.01 moles

 

90. Q: Calculate the enzymatic activity of an enzyme that converts 0.001 moles of substrate per minute.

    A: Enzymatic activity = amount of substrate converted per unit time

       Enzymatic activity = 0.001 moles/min

 

91. Q: What is the concentration of a solution if 25 mL of a 0.2 M solution is diluted to 100 mL?

    A: Concentration of diluted solution = (initial concentration * initial volume) / final volume

       Concentration = (0.2 M * 25 mL) / 100 mL = 0.05 M

 

92. Q: A protein solution has an absorbance of 0.2 at a given wavelength. Calculate the protein concentration if the molar absorptivity (ε) is 0.3 L·mol⁻¹·cm⁻¹.

    A: Concentration (c) = Absorbance (A) / (ε * path length)

       c = 0.2 / (0.3 L·mol⁻¹·cm⁻¹ * 1 cm) ≈ 0.67 M

 

93. Q: A peptide has a sequence of "ASPTYRLEU" with molecular masses of 71.1, 181.2, 128.2, 99.1, 115.1, and 99.1 Da for each amino acid, respectively. Calculate the molecular weight of the peptide.

    A: Molecular weight = sum of the masses of individual amino acids

       Molecular weight = 71.1 + 181.2 + 128.2 + 99.1 + 115.1 + 99.1 = 694.8 Da

 

94. Q: How many moles of NaCl are present in 10 mL of a 0.2 M NaCl solution?

    A: Moles of NaCl = molarity * volume in liters

       Moles of NaCl = 0.2 M * 0.01 L = 0.002 moles

 

95. Q: If a reaction follows first-order kinetics with a rate constant of 0.06 s⁻¹, what is the half-life of the reaction?

    A: Half-life (t1/2) = ln(2) / rate constant

       t1/2 = ln(2) / 0.06 s⁻¹ ≈ 11.55 seconds

 

96. Q: A buffer contains 0.2 M acetic acid (pKa = 4.76) and 0.4 M sodium acetate. Calculate the pH of the buffer.

    A: pH = pKa + log([A-]/[HA])

       pH = 4.76 + log(0.4/0.2) ≈ 4.76 + 0.301 ≈ 5.06

 

97. Q: Calculate the specific activity of an enzyme with an enzymatic activity of 50 units and a protein concentration of 0.1 mg/mL.

    A: Specific activity = enzymatic activity / protein concentration

       Specific activity = 50 units / 0.1 mg/mL = 500 units/mg

 

98. Q: How many moles of glucose are present in 10 mL of a 0.2 M glucose solution?

    A: Moles of glucose = molarity * volume in liters

       Moles of glucose = 0.2 M * 0.01 L = 0.002 moles

 

99. Q: Calculate the rate constant (k) for a first-order reaction with a rate of 0.01 M/s when the initial concentration of the reactant is 0.1 M.

    A: Rate = k * [A]

       k = Rate / [A] = 0.01 M/s / 0.1 M = 0.1 s⁻¹

 

100. Q: A buffer solution has a pH of 7.0 and contains 0.2 M acetic acid (pKa = 4.76) and 0.4 M sodium acetate. Calculate the ratio of [A-] to [HA] in the buffer.

     A: [A-] / [HA] = 10^(pH - pKa)

        [A-] / [HA] = 10^(7.0 - 4.76) ≈ 10² ≈ 100

 

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