Lab3 Report

4. The %Mn in steel can also be determined spectrophotometrically by oxidizing the manganese to the intensely colored permanganate, MnO4-. Standard solutions of permanganate gave the following absorbances (in a 1 cm cell): ABSORBANCE CONC. OF MnO4 (g/mL) 0.210 1.05 x 10-5 0.315 1.61 x 10-5 0.429 2.21 x 10-5 0.599 2.98 x 10-5 0.801 4.04 x 10-5 The following samples of steel were thoroughly reacted to convert the manganese into permanganate and then diluted to 500.00 mL. WT. OF STEEL (g) ABSORBANCE 0.5886 0.611 0.3498 0.359 0.4555 0.482 Again using Excel, plot the calibration data and calculate the %Mn in the steel.

calculate the [FESCN2+] using volumes of stock solutions. Presume that all of the SCN- ions react. Next, record the light absorbance values of each standard solution. Volume Volume Volume [FESCN2+] Absorbance Standard Fe(NO3)3 SCN- H2O sample (mL) (mL) (mL) 1 2.50 2.00 20.50 0.1811 2 2.50 1.50 21.00 0.3219 2.50 1.00 21.50 0.4981 4 2.50 0.50 22.00 0.6328 Stock [Fe(NO3)3] = 0.200 M, Stock [SCN-] = 0.0020 M. %3D

We can determine the copper(II) ion content of a sample using spectrophotometry. The following data was collected. Construct a calibration plot and determine the slope. Absorbance 0.065 0.205 0.338 0.474 0.598 2.3 x 10-3 3.3 x 104 3.1 x 10-5 3.3 x 10-2 [Cu²+], M 2.00E-06 6.00E-06 1.00E-05 1.40E-05 1.80E-05

4. To analyze the Cu(NO3)2 unknown solution in Part 3, your group constructed a plot of absorbance vs. concentration, commonly called a calibration curve or standard curve. The absorbance at the top of the peak (i.e., at the wavelength of maximum absorbance) was chosen for these measurements. What is the potential advantage of using the wavelength of maximum absorbance, rather than some other wavelength? Can you think of a situation in which you might want to choose a different wavelength? (Hint: Scientists often do not have the luxurý of analyzing pure substances dissolved in distilled water!)

6. Blue Blue dye stock solution 0.293 M Absorbance at 630 nm 0.00265 Calibration curve y = 0.0833x A solution is prepared by diluting 2.79 mL of the blue dye stock solution to 25.00 mL. The measured absorbance for the prepared solution is listed in the data table. (a) What is the theoretical molar concentration? [Blue]theoretical x 10 |M (b) What is the experimental molar concentration? [Blue]experimental x 10 M (c) What is the percent error? Percent error (blue) = %

ll中国移动 4G 11:40 PM © 1 26% O electrochemistry homework 2. 简答题 Calculate the volume of hydrogen produced at r.t.p. when a concentrated aqueous solution of sulfuric acid is electrolysed for 15.0min using a current of 1.40A. (F= 96500 Cmol-1; 1 mole of gas occupies 24.0 dm³ at r.t.p.) 输入答案 2/2 答题卡 提交 <上一题 (+

Write a one or two paragraphs of -what was study in Introduction to Equilibrium Le Chateliers Principle -Summarize what happened in these results shown below -what results did this experiment end up with whether this lab was successful or not

explain the mechanism

Nernst equation for pair MnO4 |Mn*: RT a(MnO,)a*(H*) In nF E = E° + a(Mn²*) RT a(MnO,)a(H*) E = E° + -lg nF a(Mn²*) RT, a(MnO, )a*(H*) a(Mn²*) E =E° – -In nF nF E = E° + RT la(MnO,)a*(H*) a(Mn²*)

Please help!

2) What are the values of E, pe and AG for the reaction in 1-i) when pH=8, [Mn²+]=10-4 M, [12(aq)]=10-6 M and [I]=10-³ M? Is the reaction at equilibrium? If not, which direction is it proceeding under these conditions?

Fe3+(aq) + SCN (aq) Fe(SCN)2*(aq) How was the equilibrium concentration of Fe(SCN)2+(aq) measured for the purpose of determining the equilibrium constant K? A. By ensuring that SCN- was not in excess relative to Fe3+(aq). B. By measuring the absorbance of the equilibrium samples and using the Beer-Lambert law to determine [Fe(SCN)2+]equ- C. By plotting the absorbance of Fe(SCN)2+(aq) versus concentration and determining the slope. D. By writing the equilibrium constant equation and solving it for [Fe(SCN)2+]equ- E. [Fe(SCN)2+]egu was taken to be equal to the initial concentration of SCN. Jequ

BMB 4210: Sample problems A+B C+D 20°C AG° = 4 KJ/mol A = 90mM [B] = 15M = 4M D = 300MM R= 8.314 J/mol●K %3D %3D %3D Calculate AG for the above reaction and indicate whether the reaction is favorable or unfavorable and explain how you know.

The nitrite in a series of standard solutions (mg/L, n = 5) are converted to azo dye and the slope of the calibration curve is 2.0 ppm. A 10.00-mL mineral water sample is treated in the same way as standards and diluted to a final volume of 100.00-mL It gives an absorbance of 0.80. The absorbance of blank solution under the same conditions is 0.10. Calculate ppm (mg/L) of NO2 (46 g/mol) and the molarity of NaNO2 (69 g/mol) in the original sample

4. Using the calibration curve below, what is the concentration of a Cu2t solution which had an absorbance of 0.450? Absorbance as a Function of Concentration of Cu2+ 0.800 0.700 0.600 0.500 0.400 0.300 0.200 0.100 0.000 0.800 0.700 0.600 0.500 0.400 0.300 0.100 0.200 0.000 [Cu2] EXPERIMENT 7 121 Absorbance

A solution of potassium permanganate of unknown concentration was analyzed against a standard of various concentrations. Refer to the following data set to answer the succeeding questions (MM KMNO4 = 158.034 g/mol). Table 1. Data for Standard Calibration Curve KMN04 Standard Absorbance at 525 nm (grams/Liter) 0.008 0.10437 0.158 0.20197 0.316 0.45288 0.474 0.68232 0.632 0.89361 Table 2. Data for KMNO4 Solution of Unknown Conc. Sample of Unknown Absorbance at 525 nm Conc. Undiluted 0.95423 KMN04 Diluted KMNO4 0.46514 (50% dilution) Which of the following linear equation for the standard calibration curve is generated from Table 1? y= 0.74923x – 0.03231 y= 0.03231x –0.74923 y= 1.3179x + 0.04845 y= 0.04848x + 1.3179 O O O

1. A student collects the following data for the absorbance of a complex measured in 1.00 cm spectrophotometric cells. The molar absorptivity (ɛ) of the complex under investigation is 0.750 L/mol·cm. Calculate the concentration of the solution at each time of the reaction. Measured Complex Concentration Time (min) Absorbance (M) 0.000 1.500 10.000 1.313 20.000 1.125 30.000 0.938 40.000 0.750

In an experiment on UV-Vis Spectrophotometry, What are the results for A and B? A. Calibration Curve Concentration of Cu2+ solution                      Absorbance Molarity (M) ppm Cu     0.010     .0965 0.020     0.199 0.030     0.3235 0.040     0.4385 0.050     0.5543 0.060     0.6652 0.070     0.7239 0.080     0.8463 0.090     1.0354 0.100     1.3572 B. Unknown Analysis Trial Absorbance ppm Cu 1 0.4681   2 0.5074   3 0.4297   Average ppm Cu in sample Standard Deviation % Relative Standard Deviation

please atten abc and d there are all subparts of the same question . Please respond asap thank you so much ! I appreciate it.

Best-fit line equation?

I really need help calculating the following values please!! (make sure unrounded values have 4 or more sig figs).

13. The standard free energies of formation of several species are: kJ/mol H*(aq) -237.0 H2O(1) CH3OH(aq) НСООН(аq) -163.0 -351.1 e What is the standard reduction potential of methanoic acid in aqueous solution (i.e., for HCOOH + 4H* + 4e → CH3OH + H2O)?

Pls help ASAP

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