Assignment #4 Solution (2)

Question 2. (B) the DART source (direct analysis in real time) is a relatively new MS technique. What is it and how does it work? What is it useful for?

urses/ 2951 2. A linear standard curve of KMnO4 is prepared from a set of standard solutions by plotting absorbance (y) vs. concentration (x). Use Logger Pro (as described in the Data Analysis for this experiment), or Google Sheets/Excel, to plot this standard curve using the data in Table 1. Help with spreadsheets [PDF] Table 1: Data for the standard curve of KMnO4 Absorbance Concentration (M) 0.372 6.00 x 10-4 0.298 0.223 0.149 0.0744 After plotting the standard curve, enter its slope below (not the equation of the line). Report your answer to 3 significant figures. If your answer ends in one or more zeros, use scientific notation. Slope = 4.80 x 10-4 3.60 x 10-4 2.40 x 10-4 1.20 x 10-4 M-1 M 3. Suppose that an unknown sample is analyzed spectrophotometrically at the same wavelength that was used for the standard curve and the absorbance was found to be 0.186. Use the standard curve to find the concentration of the unknown. Hint:

50 Percentage Red No. 40 Soln 100% 80% 60% 40% Table 4.1: Dilutions of Red No. 40 & Absorbance Volume of Red No. 40 Soln (mL) 10me 8mL опи 4mL Percentage Red No. 40 Soln 100% 80% 60% 40% 20% Volume of DI Water (mL) OML 2mL LIML M UML 8ML Table 4.2: Dilutions of Red No. 40 & Absorbance Concentration Red No. 40 2. Report the wavelength with the maximum absorbance of Red No. 40 dye. Absorbance 20% 2ML Part A: Making a Calibration Curve for Beer's Law 1. Calculate the concentrations of each of your diluted Red No. 40 solutions and add these to Table 4.2. Show at least one sample calculation in the space below. 0.251 0.192 Total Volume 0.181 0·119 0.060 (mL) 10 mL 10 mL 10 mL 10 mL 10 mL

Please answer. Urgent.  Thank you.

(2) A CHEM 215 student performed 5 measurements of the wt% of SO4²- of a solid power sample. The results are 8.75%, 8.85%, 8.89%, 8.71%, 8.64%. The standard deviation is 0.10%. What is the confidence interval for this student's experiment at 95% confidence level. The t values for 95% confidence for degree of freedom from 1 to 5 are 12.71, 4.303, 3.182, 2.776, 2.571, respectively. Show your work!

Internal standard. A solution containing 3.47 mM X (analyte) and 1.72 mM S (standard) gave peak areas of 3 473 and 10 222, respectively, in a chromatographic analysis. Then 1.00 mL of 8.47 mM S was added to 5.00 mL of unknown X, and the mixed solution was diluted to 10.0 mL. This solution gave peak areas of 5 428 and 4 431 for X and S, respectively. (a) Find the response factor for X relative to S in Equation 5-9. (b) Find [S] (mM) in the 10.0 mL of mixed solution. (c) Find [X] (mM) in the 10.0 mL of mixed solution.(d) Find [X] in the original unknown.

Internal standard. A mixture containing 12.8 mM analyte (X) and 44.4 mM standard (S) gave chromatographic peak areas of 306 for X and 511 for S. A second solution containing an unknown quantity of X plus 55.5 mM S had peak areas of 251 for X and 563 for S. Find [X] in the second solution.

6. This is the TLC plate for the solvent: Ethanol 50% / ethyl acetate 2. 50% V is crystal violet, G is bromocresol green and R is methyl Red. Determine the Rf for each one (Report to 2 # after the decimal) HTML Editor B IUA A 工E三ョ x x 三三 ▼ 目 回 深 T 1 12pt Paragraph 7. 3. 4 5 1. #4

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Find the Mass Spec

Types of Error; Propagation of Uncertainty from Random ErrorYou prepare an NH3 [FM 17.030 5 (±0.000 2)] solution by diluting 7.36 (±0.03) mL of a 28.00 (±0.05) wt% NH3 solution [density = 0.899 (±0.003) g/mL] to a final volume of 500.00 (±0.02) mL. Find the molarity of the NH3 solution along with its absolute uncertainty.

MS: m/z=148 (M,100%),149 (11%) IR (liquid film): 3077­‐2835 (multitude of weak peaks) 1640(m),1611(m),1511(s),1301(m),1247(s),1176(s),1038(s),922(m),914(m) and 810(m)cm^-1 There are no absorptions in the 3100-­‐4000cm^-1 region of the spectrum. (m=medium absorption, s=strong absorption). Choose (circle) the best structure for estragole (W) from the four possible structures (1-­4)shown below. Explain briefly how you eliminated each of the incorrect structures for W.

CPU/RAM ProctorU e Proctor e Proctoru o.com/collab/ui/session/join/43918c0bf9cb421ca7b98b0075f5f239 Firefox Ex SPECTROSCOPY 1. If the concentration of solute in a solution is high, the Absorbance will be high or low and why? 2. Was the spectroscopy experiment qualitative or quantitative analysis? 3. If we have 12M HCI and we need 3 L of 1M HCI, how much 12 M should we use? 4. What does Molarity mean? 5. When must safety goggles be worn? 6. If you make a mistake recording data, what must you do? spec hw.pptx (2/3) ..% An

How to interept this data to match the structure? It gives the peak/PPM and having trouble matching it up. Does the intensity of the peak mean something? If possible, please draw it with thr associated peaks/ppm's.

Questions 1 and 2

2 (1) When performing chemical measurements, replicate experiments are often needed. This is to mitigate (Systematic or Random) error. (2) A CHEM 215 student performed 5 measurements of the wt% of SO4²- of a solid power sample. The results are 8.75%, 8.85%, 8.89%, 8.71%, 8.64%. The standard deviation is 0.10%. What is the confidence interval for this student's experiment at 95% confidence level. The t values for 95% confidence for degree of freedom from 1 to 5 are 12.71, 4.303, 3.182, 2.776, 2.571, respectively. Show your work!

Calculate the theoretical yield of the product. The recorded weight of the product was 3.48grams. Use this information and the UV-vis data to calculate the theoretical yield of the product.

What is 4d?

A3

A third spectrophotometric method for the quantitative analysis of Pb2+ in blood uses Cu2+ as an internal standard. A standard containing 1.75 ppb Pb2+ and 2.25 ppb Cu2+ yields a ratio of (SA/SIS)std of 2.37. A sample of blood is spiked with the same concentration of Cu2+, giving a signal ratio, (SA/SIS)samp, of 1.80. Determine the concentration of Pb2+ in the sample of blood.

You prepared a stock solution by dissolving a compound with the molar mass of 110.65 in a 100 mL volumetric flask. Then you removed a 2 mL aliquot and placed it in a 250 mL volumetric flask and dilute it to the mark. The absorbance of this diluted solution in the 250 mL volumetric flask at 288 nvm was 0.421 using a 2.50 cm path length curvet. The molar absorptivity for this compound at 288 nvm is 65000 M-1cm-1 How many ng of the compound were used to make the stock solution?  a)1.44 b)0.96 c)0.72 d)1.22 e)2.87

pls help fill in the missing parts