From the additional information,
Absorption Maximum |
Molar Absorptivity |
||
| Species | nm | 430 nm | 600 nm |
| HIn | 430 | 8.04 ´ 103 | 1.23 ´ 103 |
| In- | 600 | 0.775 ´ 103 | 6.96 ´ 103 |
| 所組別： | 化學學系 | 科目： | 分析化學 | 考試時間： | 6月14日第2節 |
請正確且詳盡的書寫解題或計算過程，以便能得完整分數
| 1. | (i) | Derive an equation to yield the value of [H3O+] for amphiprotic salts NaHA. |
| (ii) | Calculate the pH of the first equivalence point for the titration of 25.00 mL of 0.1000 M maleic acid, HOOC- CH=CH- COOH, with 0.1000 M NaOH.Note: Ka1 = 1.3 ´ 10-2; Ka2 = 5.9 ´ 10-7 (20 points) |
| 2. | The equilibrium constant for the conjugate acid/base pair is From the additional information,
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| (i) | calculate the absorbance at 430 nm and 600 nm for the following indicator concentrations: 3.00 ´ 10-4 M, 2.00 ´ 10-4 M, 1.00 ´ 10-4 M, 0.500 ´ 10-4 M, and 0.250 ´ 10-4 M. |
| (ii) | plot absorbance as a function of indicator concentration. What do you conclude from this plot? (35 points) |
| 3. | Ten-millimeter aliquots of a natural water sample were pipetted into 50.00 mL volumetric flasks. Exactly 0.00, 5.00, 10.00, 15.00, and 20.00 mL of a standard solution containing 11.1 ppm of Fe3+ were added to each, followed by an excess of thiocyanate ion to give the red complex Fe(SCN)2+. After dilution to volume, absorbances for the five solutions, measured with a photometer equipped with a green filter, were found to be 0.240, 0.437, 0.621, 0.809, and 1.009 respectively (0.982 cm cells). (45 points) |
| (i) | What was the concentration of Fe3+ in the water sample? |
| (ii) | Calculate the standard deviation of the slope, the intercept, and the concentration of Fe3+. |
| Note: (1) | To find the sloe and intercept of a linear equation y = mx + b,
you may use the following formulas |
| (2) | The standard deviation Sy of the residuals: The standard deviation of the sllope:  The standard deviation of the intercept:  
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