General Practical Chemistry I — integral Past Questions

University of Ilorin CHM107: 45 questions.

Topics: Treatment of Analytical Data, Precipitation Titration, Volumetric Analysis, Gravimetric Analysis, Scientific Data and Chemical Experiments, Acid-Base Titration, Oxidation-Reduction Titration, Complexometric Titration

  1. A 1.963 g sample of an alloy dissolves in nitric acid and is diluted to volume in a 100 mL volumetric flask. Titrating a 25 mL portion with a 0.1078 M KSCN requires 27.19 mL to reach the end point. Calculate the %W/W Silver in the alloy.
    1. 84.4%
    2. 64.4%
    3. 25.6%
    4. 32.3%
  2. Manganese in a 1.52 g sample was precipitated as Mn₃O₄ (FW = 228.8) weighing 0.126 g. Find the percentage of Mn (FW = 54.94) in the sample.
    1. 8.97%
    2. 6.97%
    3. 5.97%
    4. 7.97%
  3. Which of these is not a determinate error?
    1. Operative error
    2. Methodic error
    3. Instrumental error
    4. Constant error
  4. Which of the following has the greatest precision?
    1. Gravimetric analysis
    2. Volumetric analysis
    3. Precipitation titration
    4. Complexometric titration
  5. How many bonding sites does EDTA have?
    1. 2 bonding sites
    2. 6 bonding sites
    3. 4 bonding sites
    4. 8 bonding sites
  6. The following measurements were obtained for a metal bar: 4.012 g, 4.022 g, 4.019 g, 4.011 g, 4.017 g, 4.018 g, and 4.024 g. Calculate the mean.
    1. 4.0175 g
    2. 4.018 g
    3. 4.01757 g
    4. 4.017 g
  7. Random errors are
    1. Avoidable
    2. Unavoidable
    3. Intentional
    4. Deliberate
  8. Which of the following methods is used in a basic medium?
    1. Mohr's
    2. Volhard's
    3. Fajan's
    4. None
  9. A method of analysis yields weights for gold that are low by 0.3 mg. Calculate the percent relative error caused by this uncertainty if the weight of gold in the sample is 800 mg.
    1. 0.04%
    2. 0.0375%
    3. 0.038%
    4. -0.04%
  10. The number of significant figures in 0.0030900 and 0.002008 are?
    1. 5 and 6
    2. 4 and 5
    3. 7 and 7
    4. 6 and 4
  11. In the analysis of chromium in three samples of stainless steel, the following results were obtained: A (6.25%, 6.24%, 6.26%), B (6.71%, 6.72%, 6.71%), C (6.05%, 6.57%, 6.32%). Suppose the true value is 6.25%, how precise and accurate are the results?
    1. A, B, C are accurate and precise
    2. Only A is accurate and precise
    3. A and B are accurate and precise
    4. A and C are accurate and precise
  12. Calculate the mean and standard deviation of the following set of analytical results: 15.67 g, 15.69 g, and 16.03 g.
    1. 15.80 and 0.20
    2. 1.580 and 2.0
    3. 15.80 and 2.0
    4. 15.80 and 0.04
  13. The true volume of a liquid is 2.55 cm³ and the measured value is 2.58 cm³. Calculate the relative error.
    1. 0.03
    2. 1.2
    3. 0.012
    4. 0.12
  14. Consider the following set of data: 4.4, 4.1, 4.2, 4.3, and 4.5. Calculate the mean and relative error if the accepted value is 4.0.
    1. 4.3, 0.075
    2. 4.3 and 0.3
    3. 4.3 and 75%
    4. 4.3 and 7.5%
  15. If a 2.62 g sample of material is analyzed to be 2.52 g, what is the absolute error?
    1. 0.10 g
    2. 0.01 g
    3. -0.10 g
    4. 0.100 g
  16. What is the weight of Fe(NO₃)₂ in grams, required to prepare 500 mL of 0.02 mol/dm³ solution? (Fe = 56, N = 14, O = 16)
    1. 0.72
    2. 18
    3. 7.2
    4. 1.8
  17. Gravimetric factor (GF) for the conversion of Ca²⁺ to CaC₂O₄ precipitate is (Ca = 40, C = 12, O = 16)
    1. 0.3125
    2. 0.4125
    3. 0.1125
    4. 0.2125
  18. Common determinate errors are __________ except?
    1. Accidental error
    2. Instrumental error
    3. Errors of methods
    4. Operative errors
  19. The oxidation number of an element in an uncombined state is ___
    1. 1
    2. 2
    3. 3
    4. 0
  20. Endpoint determination in Volhard involves
    1. Filtration
    2. Washing
    3. Fractional precipitation
    4. Masking
  21. Errors cannot be completely
    1. Studied
    2. Eliminated
    3. Avoided
    4. Known
  22. Source of contamination of precipitate in gravimetric analysis could be from?
    1. Washing
    2. Igniting
    3. Surface adsorption
    4. Weighing
  23. In gravimetric analysis, measurements are based on?
    1. Volume
    2. Density
    3. Mass
    4. Pressure
  24. The following are correct about counter ion except?
    1. Held by chemical bond
    2. Held by electrostatic attraction
    3. Opposite in charge to primary adsorbed ion
    4. Loosely held in solution surrounding precipitate
  25. In the Mohr titration method, the chloride is titrated with standard AgNO₃ solution using an indicator. Which of these is the indicator?
    1. Iron(III) (red at equivalence point)
    2. Dichlorofluorescein (yellow at equivalence point)
    3. Ag₂CrO₄ (yellow at equivalence point)
    4. Potassium chromate (yellow before equivalence point)
  26. Completeness of a precipitation reaction is determined by?
    1. The solubility of the precipitate formed
    2. The duration taken for the reaction to occur
    3. The concentrations of the reacting mixtures
    4. The color of the precipitate formed
  27. In the titration of Br⁻, which titrant(s) is/are used?
    1. AgNO₃
    2. AgNO₃, KSCN
    3. KSCN
    4. AgNO₃ & AgNO₃, KSCN
  28. Which of the following indicators has a yellow colour at pH of 10?
    1. Bromocresol green
    2. Phenol red
    3. Thymol blue
    4. Alizarin yellow
  29. What is the colour of methyl orange at a pH of 12?
    1. Red
    2. Yellow
    3. Orange
    4. Blue
  30. Which of these indicators can be used for a weak acid and a weak base?
    1. Methyl orange and phenolphthalein
    2. Methyl red and methyl orange
    3. Phenolphthalein and methyl red
    4. No suitable indicator
  31. A loss of 0.4mg of Zn occurs in the course of an analysis for that element. Calculate the relative error due to this loss if the weight of Zn in the sample is 400mg.
    1. 1.0%
    2. -1.0%
    3. 0.1%
    4. 0.2%
  32. A solution with pH = 2 is more acidic than one with pH = 6 by a factor of?
    1. 4
    2. 12
    3. 400
    4. 10,000
  33. 1500 mL of a 15 ppm solution of potassium hydroxide contains how many mg of potassium hydroxide?
    1. 30 mg
    2. 15 mg
    3. 22 mg
    4. 25 mg
  34. In precipitation gravimetric methods, analyte is converted to
    1. A sparingly soluble precipitate of known composition
    2. A colloidal precipitation of known composition
    3. A soluble precipitation of known composition
    4. A precipitate that reacts with atmospheric constituents
  35. In the precipitation of chloride ion as silver chloride, all these ions are interferences except?
    1. Cyanide ion
    2. Nitrate ion
    3. Bromide ion
    4. Iodide ion
  36. The Ksp for the ionization of AgCl in water is given by
    1. [H⁺][Cl⁻]
    2. [Ag⁺][OH⁻]
    3. [Ag⁺][Cl⁻]
    4. [H⁺][OH⁻]
  37. The titration useful for determining chloride in neutral or unbuffered solutions such as drinking water is?
    1. Volhard titration
    2. Acid-base titration
    3. Adsorption indicator
    4. Mohr titration
  38. Meso analysis represents particles of what size?
    1. 10⁻¹ to 1
    2. 10⁻² to 10⁻¹
    3. 10⁻³ to 10⁻²
    4. 10⁻⁴ to 10⁻³
  39. Bromocresol green and bromothymol blue have what color change in acidic medium respectively?
    1. Pink, colorless
    2. Red, blue
    3. Yellow, yellow
    4. Yellow, red
  40. Indirect determination of [PO₃]³⁻ by precipitating HgCl₂ is an example of
    1. Volatilization method
    2. Precipitation method
    3. Electrogravimetry
    4. Particulate method
  41. Chemical analysis concerned with how much of a substance present in a sample is
    1. Quantitative analysis
    2. Qualitative analysis
    3. Volumetric analysis
    4. Theory and practice
  42. EDTA is
    1. Hexadentate
    2. Tridentate
    3. Chloride ion
    4. Bidentate
  43. Precipitate must be
    1. Readily filterable and washable
    2. Filterable and soluble
    3. Filterable and not washable
    4. Not filterable, not washable
  44. An ultrapure compound that serves as the reference material for a titrimetric method of analysis is known as
    1. A secondary standard
    2. A primary standard
    3. A standard solution
    4. A pure solution
  45. If three litres of a solution of H₃PO₄ contains 294 grams of H₃PO₄, what is the normality of the solution? (Atomic weights: H=1, O=16, P=31)
    1. 0.1
    2. 1.0
    3. 3.0
    4. 9.8

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