instrumental answer 2

Cairo University Faculty of Science Chemistry Department

Mid Term Exam Analytical Chemistry

Third Year Special Chemistry

Name:………… Code No.: ……… Time: 20 min

Answer the Following Questions I. Mention only three factors affecting the bond properties and absorption trends in IR spectroscopy? Illustrate by examples. ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… II. Calculate the approximate position of the stretching frequency bands corresponding to C=C, C-H and C-D bonds. (K = 5, 10 and 15 dyne/cm for single, double and triple bonds respectively). ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ………………………………………………………………………………………………………

III. Circle the Correct Statement 1. Fluctuations in flame temperature have major direct effects on a. Atomic emission spectroscopy b. The number of atoms in excited state c. Both a and b d. Atomic absorption spectroscopy 2. Higher temperatures have several effects on atomic spectroscopy where a. Better sensitivities are obtained at higher temperatures b. Line broadening will increase as temperature is increased c. Increased ionization is observed at higher temperatures d. All of the above 3. The usual liquid sample introduction technique in atomic spectroscopy is a. Laser ablation b. Glow discharge technique c. Nebulization d. All of the above 4. Electrothermal atomizers are d. Discrete atomizers b. Faster than flame atomizers c. Used for direct analysis of nonmetallic samples without sample pretreatment d. All of the above 5. Chromium is known to form the oxide, especially at high flame temperatures, determination of Cr is suggested to take place a. As close as possible to burner tip b. As far as possible to burner tip c. Using a fuel rich flame d. At low temperature 6. The following statement(s) is (are) true a. Electrothermal methods are more sensitive than flame methods b. Small sample volumes are required in electrothermal methods c. High velocity burning flames can be used in premix burners d. All of the above 7. The source in atomic absorption spectroscopy should be a line source rather than a broad band source since a. The bandwidth of the incident radiation must be much wider than the atomic line width b. Even good monochromators can not provide narrower bandwidths than the atomic line width c. Atoms will not absorb broad band spectra d. None of the above 8. A laminar flow (premix) burner is characterized by a. Higher sensitivity than a turbulent flow burner b. Homogeneous mixing of fuel, oxidant and sample c. Longer path length than a turbulent flow burner d. All of the above 9. Samples can be introduced into an atomic emission instrument based on an arc by several methods including a. Nebulization of a solution b. Converting the sample into the hydride form c. Homogeneous mixing of the sample with fuel and oxidant d. None of the above 10. Organic solvents are sometimes used in AAS where a. Improved nebulization efficiency is obtained c. More scattering could be observed

b. Lean flames must be used d. All of the above