Questions on Instrumental Methods of Analysis

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1 Questions on Instrumental Methods of Analysis 1. Which one of the following techniques can be used for the detection in a liquid chromatograph? a. Ultraviolet absorbance or refractive index measurement. b. Increase in temperature c. Ionization in flame d. Thermal conductivity 2. Considering high performance liquid chromatography, which one of the following statements is FALSE? a. HPLC is suitable for the separation and determination of the nonvolatile (high boiling point) components. b. The stationary phase could be a liquid or a solid. c. Columns longer than 50 meters have been used here to increase the efficiency of separation. d. High pressure is used here to decrease the retention time and improve the separation of components. 3. According to Beer s law for a colored solution, which one of the following statements is False? (a) The percent transmission is not directly proportional to the concentration. (b) The absorbance is directly proportional to the concentration. (c) The absorbance does not change when the cell path length (cell thickness) increases. (d) When the concentration of the unknown sample is higher than the highest concentration in the calibration range, the sample should be diluted. 4. Deuterium and tungsten lamps are used as a light source in one of the following techniques. (a) Nuclear magnetic resonance spectrophotometers (b) X-rays diffractometers (c) Gas chromatograph (d) Uv/Visible spectrophotometers 5. Which one of the following arrangements for the sequence of the main components of a Uv/visible spectrophotometer is Correct? (a) Light source Monochromator Sample cell Detector Readout (b) Light source Detector Sample cell Monochromator Readout (c) Light source Sample cell Detector Monochromator Readout (d) Light source Readout Sample cell Detector Monochromator 1

2 6. Considering the electrochmical cells, which one of the following statements is False? (a) Galvanic cell is that in which a spontaneous chemical reaction takes place and an electrical energy is produced. (b) A nonspontaneous chemical reaction is forced to occur in the electrolysis cell. (c) The salt bridge is used to allow for the movement of electrons from the solution of one half cell to the other (d) The cathode is the electrode at which reduction takes place. 7. which one of the following radiation has the longer wavelength a- infra red b- visible c- x-ray d- ultra violet e- gamma rays 8. The energy associated with infra red is enough to make a- electronic transitions b- vibrational and rotational transitions c- a full separation of the electron in the outer shell d- X-ray fluorescence e- an electron move from an inner orbital 9. The moisture in an organic substance is determined by a- potentiometric titration b- X-ray fluorescence c- X-ray absorption d- Karl Fisher titration e- Measuring the ph of the system 10. The technique used to identify a functional group in an organic molecule is a- coulometry b- X-ray fluorescence c- Infrared spectrometry d- Karl Fisher titration e- Conductimetry 2

3 11. One part per million is the same as (a) 1 g/g (b) 1 mg/kg (c) 1 ng/mg (d) All of the above are correct 12. Narrow line spectra are emitted by (a) hot solids (b) excited polyatomic molecules (c) molecules in the ground molecular state (d) excited atoms 13. What are the dimensions of the molar absorptivity in the Beer's law expression? (a) Moles per liter (b) Liters per mol.centimeter (c) Grams per mole (d) Micrograms per square centimeter 14. The region of the electromagnetic spectrum in which the highest energy photons are observed is the (a) ultraviolet (b) infrared (c) microwave (d) x-ray 14. An important advantage of a double-beam spectrophotometer over a single-beam spectrophotometer is that (a) it permits cancellation of slow variations of the source power (b) it requires same light source for Uv, Vis, and Infra red radiation (c) it can be used in conjunction with rapid response detection systems (d) a greater range of wavelengths can be used 3

4 15. Grating is a device used in the spectrophotometer to function as (a) a light source (b) a monochromator (c) a detector (d) a nebulizer 16. Helium rather than argon, often is used as the carrier gas in GLC when TCD is used as the detector because, (a) He has a higher ionization potential (b) He is more inert (c) He has stable isotopes which separate and cause a change in column behavior. (d) He has a higher thermal conductivity 17. To deionize laboratory water by ion-exchange, the best approach employs (a) a column containing a strong acid cation exchanger in the hydrogen form (b) a column containing a strong base anion exchanger in the hydroxyl form (c) a mixed bed column containing a strong acid cation exchanger in the sodium form and a strong base anion exchanger in the hydroxyl form (d) a mixed bed column containing a strong acid cation exchanger in the hydrogen form and a strong base anion exchanger in the hydroxyl form 18. Reversed phase HPLC is the technique in which (a) stationary phase is solid and mobile phase is liquid. (b) the stationary phase is made of very fine particles. (c) the stationary phase is non polar and the mobile phase is relatively polar. (d) the stationary phase has been silinized with dimethyldichlorosilane. 19. Considering high performance liquid chromatography, which one of the Following statements is FALSE? (a) HPLC is suitable for the separation and detrmination of the nonvolatile species. (b) The stationary phase used in the HPLC column could be relatively polar or nonpolar liquid. (c) The separation efficiency has been increased by decreasing the particle size of the solid support for the stationary phase. (d) Very long columns have been used here to increase the effecirncy of separation. 4

5 20. Considering the electrochmical cells, which on of the following statements is TRUE? a. Electrons move from the cathode towards the anode b. Cations move from the cathode towards the anode c. A nonspontaneous chemical reaction is forced to occur in the electrolysis cell d. The salt bridge is used to allow for the movement of electrons from one half cell to the other 21. How should the concentration of a colorless sample be determined? A. Using a UV spectrophotometer B. Using a VIS spectrophotometer C. Either a UV or VIS spectrophotometer D. Using an indicator solution and ph paper 22. In mass spectrometry, the atomic mass unit, amu, is defined as a. 1/12 of the mass of one neutral C-12 atom b. the mass of any individual atom expressed in grams c. the mass of a deuterium atom d. the mass of one mole of hydrogen atoms expressed in daltons 23. Which one of the following statements is true regarding the inlet system of a mss spectrometer? a. It should operate at very low pressure and high temperature b. It operates normally at the atmospheric pressure c. It allows evaporation of the samle at high temperature and high pressure d. The sample molecules are converted into ions in the inlet system of the mass spectrometer 24. What happens to the molecules in the ion source of the mass spectrometer? a. They are ionized and split in fragments b. They are ionized only c. They lose hydrogen atoms only d. They are excited and emit radiation at vsarious wavengths 5

6 25. How many equivalent NMR protons are in butanoic acid? A) 8 B) 2 C) 6 D) The calculation ( ) / should be reported as (1) (2) (3) (4) 0.12 Answer = Which of the following is true? (1) If an analysis is accurate, it must also be precise. (2) A precise analytical measurement will always have a small relative standard deviation. (3) If an analysis is reproducible, it will be accurate. (4) None of the above. Answer = 2 28.The wavenumber of a transition is 2000 cm 1. In what part of the electromagnetic spectrum does this come? a. Infrared. b. Radiowave. c. Microwave. d. Ultraviolet-visible. 29.The frequency of a transition is Hz. What is the corresponding wavelength? a m b. 560 nm c m d cm According to the Beer-Lambert Law, on which of the following does absorbance not depend? a. Extinction coefficient of the sample. b. Colour of the solution. c. Distance that the light has travelled through the sample. d. Solution concentration. 6

7 31.What is the name of an instrument used to measure the absorbance of a coloured compound in solution? a. Colourmeter. b. Calorimeter. c. Colorimeter. d. Coulometer. 32. A solution of X of concentration mol dm 3 gives an absorbance of 0.5. What concentration is a solution of X which gives an absorbance reading of 0.25? Assume that the same optical cell is used for both readings. a mol dm 3 b mol dm 3 c mol dm 3 d mol dm The dichromate ion absorbs light of wavelength close to 500 nm. Based on this information, what can you conclude? a. Solutions of the dichromate ion are colorless. b. The dichromate ion absorbs within the visible region. c. The dichromate ion absorbs in the ultraviolet region. d. The dichromate ion absorbs outside the visible region. 34. Which of the following statements is correct? a. Solution concentration. b. Infrared radiation has a shorter wavelength than visible light. c. Infrared radiation has a lower wavenumber than visible light. d. Microwave radiation possesses more energy than infrared radiation. e. Ultraviolet radiation has a longer wavelength than infrared radiation. 35. Which statement is correct? a. Wavelength is directly proportional to energy. b. Wavenumber is directly proportional to wavelength. c. Wavelength is directly proportional to frequency. d. Wavenumber is directly proportional to energy. 7

8 36. Aqueous KMnO 4 solutions are purple. A plot of absorbance against concentration is: a. non-linear. b. linear with a negative gradient. c. linear with a positive gradient. d. an exponential curve. 37.A shift to lower wavenumber for an absorption in a spectrum corresponds to: a. a loss of intensity. b. a shift to lower wavelength. c. a shift to higher energy. d. a shift to lower frequency. 38. The UV/VIS spectroscopy a. generates colored spectrums b. can determine the concentration c. can be used to make light visible 39. The UV/VIS spectroscopy a. generates colored spectrums b. can determine the concentration c. can be used to make light visible 40. The extinction coefficient is a. a constant of a substance b. a universal constant c. equal to one 41. At the doubled concentration a. the wave length of the absorption is different b. the extinction coefficient is twice as large c. the extinction is twice as large 8

9 41. The units of an IR spectrometer on the X-axis is a. meter b. centimeter c.per centimeter 42. The unit of an NMR spectrum on the X-axis is a. Hertz b.ppm c. cm A triplet is a. a triple linear signal b. three signals c. three spectrums 44. In a mass spectrometry, a. the analyzed substance remains intact b. large quantities of the substance is required c. the analyzed substance is ionized 45. A mass spectrometry delivers the evidence about a. the color of a substance b. the molecular mass of a substance c. the reactivity of a substance 9

3) In CE separation is based on what two properties of the solutes? (3 pts)

3) In CE separation is based on what two properties of the solutes? (3 pts) Final Exam Chem 311 Fall 2002 December 16 Name 1) (3 pts) In GC separation is based on the following two properties of the solutes a) polarity and size b) vapor pressure and molecular weight c) vapor pressure