大连理工大学20xx年一月分析化学(英强)C

大连理工大学

课程名称：分析化学（英强）试卷： C 闭卷

授课院 (系)：化工学院考试日期： 2008 年 1 月 8 日试卷共 6 页

Ⅰ. Judgments (10 points)

1. Precision indicates the closeness of the replicate measurement in a set. ( )

2. The weak acids H3BO3 (pKa=9.24) and CH3COOH (pKa= 4.75) can be titrated with standard alkaline solution directly. ( )

3. The pH transition range of an acid-base indicator should be dependent on its pKHIn, and falls in the titration curves partially or completely. ( )

4. In complexometric titration, an effective method for titrating the metal ions step-by-step is to mask the interfering ions. ( )

5. In potentiometry, the liquid junction potential is developed owing to the differences in sizess of the ions at the interface. ( )

6. The maximum molar absorptivity emax is a property of a substance. The sensitivity of the determination will be low for a large emax value. ( )

7. In gas chromatography, a large partition coefficient K of a component indicates that the concentration of the component in the mobile phase is large, and then the retention time is long. ( )

8. In Infrared absorption spectroscopy (IR), the prerequisite for determination of a functional group –C=CH is that the fundamental line of the functional group in different compounds appears at certain range. ( )

9. In 1HNMR method, we choose the compound (CH3)4Si (TMS) as the internal standard (its d=0) because the shielding parameter for the protons in this compound is smaller than for most other protons. ( )

10. In AAS analysis, one of the perquisites for quantitative analysis is that the numbers of atoms in ground states approximate the numbers of the total atoms. ( )

Ⅱ. Choice (30 points)

1. For the following data, which contains two significant figures? ( )

(A) [H+]=0.012mol×L-1 (B) pH=6.37

2. For the following statements, ( ) is wrong.

(A) the larger the Ka, the larger the titration break.

(B) the higher the concentration of the titrant, the larger the titration break.

(D) the larger the Ksp, the larger the titration break.

3. For the following sets of data which contains the value should be rejected according to Q test (Q0.90=0.76, n=4), ( )

(A) 0.1122，0.1126，0.1130，0.1134

(B) 87.50，88.50，89.00，89.50

(D) 0.2042，0.2044，0.2045，0.2047

4. For the following statements concerning αY(H) , which is wrong? ( )

(A) αY(H) decreases as pH increases.

(B) αY(H) is always less than 1.

(D) αY(H) increases as pH decreases.

5. The concentrations of the acids HCl, HAc (pKa=4.75) and HCOOH (pKa=3.75) are equal.When they are titrated with NaOH standard solution, the order of the titration breaks is ( )

（A）HCl ＜ HCOOH ＜ HAc (B) HAc ＜ HCOOH ＜ HCl

6. In the Volhard titration, ( )

(A) Cl- is titrated with AgNO3 standard solution, K2CrO4 is used as indicator and the pH range is 6.5-10.5.

(B) Cl- is titrated with AgNO3 standard solution, K2Cr2O7 is used as indicator and the medium is acidic.

(D) Ag+ is titrated with NH4SCN standard solution, ferric alum is used as indicator and the medium is acidic.

7. In potentiometry, the reference electrode should meet that ( )

(A) its potential is independent of temperature

(B) its potential should be equal to zero

(D) there is no liquid junction potential

8. In UV-Vis spectrophotometry, the reasons for the apparent deviations from Beer’s Law are ( ).

(A) nonmonochromatic radiation and the reading errors,

(B) nonmonochromatic radiation and systematic errors,

(D) operation mistakes and random errors.

9. In spectrophotometry, the suitable absorbance range is ( ).

(A) 0~0.2 (B) 0.3~1.0

10. In AAS analysis, the width of an atomic absorption line is mainly determined by ( )

(A) the natural width (B) the Doppler broadening

11. The function of the atomization system in AAS is ( )

(A) to emit characteristic radiation

(B) to provide the energy to obtain atoms that in ground states

(D) to emit electrons

12. In gas chromatography, if the baseline width of a peak decreases one times, the column efficiency will be ( ) times as the former.

(A) 2 (B) 4

13. For 1HNMR spectrum, which of the chemical shift for the following marked proton(s) in the compounds is the largest. ( )

(A) RCH2CH2OH； (B) RCH2CH2OH；

(C)RCHO； (D) C6H6.

14. In IR spectrum, the order for the absorption peaks of the functional group –C=O in the compounds (1) FCOF, (2) CH3COF, (3) CH3COCl should be ( ).

(A) (1)＞ (2) ＞ (3) (B) (2)＞ (1) ＞ (3)

15. The Doppler broadening of the atomic absorption line is from ( ).

(A) thermal movement of atoms (B) collisions between unlike atoms

Ⅲ. Fill in the blanks. (10 points)

1. The UV-Vis spectrophotometer is usually composed of , , sample container, detector, signal processors and readouts.

2. The PBE for (NH4)2C2O4 is .

3. The metal ions M and N can form complexes MR and NR with color-forming reagent R. At certain wavelength, the total absorbance for MR and NR is 0.530, and the transmittance for MR is 40%. The absorbance for NR is at this wavelength.

4. In GC analysis, the TCD is proportional to the of the substance detected, while the FID works proportionally to .

5. In 1HNMR, the peak area ratio for CH3CH2CHO from downfield to upfield is .

6. A Fe3+ solution of 10-3.10mol/L is titrated with EDTA standard solution. The minimum pH value for effective titration is , and at this pH, lgKFeY-’= . lgKFeY-=25.1

lgaY(H) 14 15 16 17

pH 1.9 1.6 1.3 1.0

Ⅳ. Calculations (42 points, 3´10 points for problems 1, 2, and 3, 12 points for problems 4)

1. A 0.2150g steel sample is dissolved in HCl solution. SnCl2 reduces the Fe3+ of this solution to Fe2+, and then Fe2+ is titrated with 0.01726mol/L K2Cr2O7 standard solution, requiring 22.32mL. Calculate , , the percentage of iron in the steel sample in terms of %Fe and %Fe2O3. (=159.7 g×mol-1, MFe=55.85 g×mol-1)

2. Weighing a sample containing Ca 0.0500g，dissovled and prepared to be a solution of 100.00mL，then the voltage of the solution is measured with a cell made up of a Ca2+ selective electrode and a reference electrode at 25℃, the voltage reading is 385.0mV; After the addition of 1.00mL 0.100mol·L-1 Ca2+ standard solution and good mixing, measure again, the voltage reading is 401.5mV. Calculate the concentration (with percentage) of Ca in the sample.

3.At 500nm, a compound A has an absorptivity 100 L·g-1·cm-1. A 0.4500g sample containing the compound A isdissolved and then prepared in a 250mL volumetric flask. Pipet a 1.00mL aliquot and then dilute to 50.00mL.The final solution has an absorbance of 0.37 when measured in a 1cm cell at 500nm. Calculate the percentage of the compound A in the sample.

4. A sample is analyzed by packed gas chromatography. When the column length is 1m, the retention times for components A and B are 11.6 min and 12.5 min respectively. Meanwhile, the theoretical plate number for the column is 3600.

Calculate:(1) the corresponding baseline widths for components A and B

(2) the resolution

(3) Assume that the ration of the retention times of the two compounds keep constant and the peak widths of the two compounds are equal, calculate the column length for the baseline separation of the two components.

Ⅴ. Deduction (8 points)

Knowing that the molecular formula of a strong-smelling compound is C3H6O2. The compound shows a wide absorption at 3400cm-1 and a strong absorption at 1710cm-1 in its IR spectrum. The 1HNMR spectrum for the compound is as follows. Deduce the structure of the compound and give the deducing procedures.

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