Interpretation
Estimate the pK4 of the acid has to be calculated.
Concept introduction:
UV/vis spectroscopy: It is deal with information about various compounds that have conjugated double, the UV light and visible light have jest the right energy to cause an electronic transition in a molecule that is to promote an electron from one molecular orbital to another higher energy.
Henderson-Hesselbalch equation: The acid lose a proton in an aqueous solution depends on the both the
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Organic Chemistry (8th Edition)
- Estimate the Ka of a weak acid from the data given below. One gram quantities of the acid were dissolved in equal quantities of the various buffer solutions and all solutions were measured under the same conditions. The anion of the acid is the only species that absorbs at the wavelength used. pH: Abs: 4 0.0 5 0.0 6 0.06 7 0.39 8 0.95 9 1.13 10 11 1.18 1.18arrow_forward1.) Beer's Law can be used to find the concentration of a solution by measuring its absorbance. The law is given by ?=???A=ϵbC Where A is the absorbance, ?ϵ is the molar absorptivity, b is the pathlength of the light (the width of the sample cell), and C is the concentration of the solution. A student is analyzing a solution of a metal, and finds that the absorbance of the solution is 0.532. If ?=187 L⋅g−1⋅cm−1ϵ=187 L⋅g−1⋅cm−1 and ?=1 cmb=1 cm , what is the concentration of the metal in solution (in g/L)? * 352 * 2.84×10−32.84×10−3 * 2.84×10−22.84×10−2 * 96.8 2.) How many significant figures does the number 0.00358 have? Group of answer choices a.1 b.2 c.3 d.5 3.) A 10.00 mL solution of a certain food dye has a concentration of 1.47 g /L. What is the total mass of food dye in the solution? Report your answer with the correct number of significant figures.arrow_forwardA student prepared four standard solutions of (NH4)2Fe(SO4)2 and measured their absorbance at 505 nm. She created a calibration plot with the best-fit line of y = 9372 x + 0.0539. She measured the absorbance of her diluted unknown sample solution as (4.69x10^-1) nm. If she prepared her diluted sample solution by diluting 10.00 mL of the original solution to a total volume of 50.00 mL with deionized water, what is the concentration of Fe2+ in her original solution? Answer in units of M. Note: Your answer is assumed to be reduced to the highest power possible.arrow_forward
- Absorbance at 453 nm 8393939 7 fl. oz./20 ml Beer-Lambert's Law (Spectrophotometry) #1 Fe (aq) + KSCN(s) FESCN "(aq) + K" (aq) 3+ To determine the moles of Fe (aq) in a 100. mL sample of an unknown solution, excess KSCN(s) is added to convert all the Fe (aq) into the dark red species FeSCN"(aq), as represented by the equation above. The absorbance of FESCN"(aq) at different concentrations is shown in the graph below. 2+ 0.50 目0.40 0.30 0.20 01 0. 0. 5 x 10-5 10 x 10-5 Concentration of FESCN2+ (M) If the absorbance of the mixture is 0.20 at 453 nm, haw many moles of Fe (aq) were present in the 100. mL sample? (Assume that any volume change due to adding the KSCN(s) Iis negligible.) 3+, 4x10-4 mol 3 x 104 mol (B) 4x 10-6 mol 3x 10-6 molarrow_forwardThe standard curve was made by spectrophotographic analysis of equilibrated iron(III) thiocyanate solutions of known concentration. You are asked to analyze a Fe(SCN)2+ solution with an unknown concentration and an absorbance value of 0.392. The slope-intercept form of the equation of the line is y = 4538.1x +0.0077. The unknown was analyzed on the same instrument as the standard curve solutions at the same temperature. What is the Fe³+ concentration of the unknown solution? [Fe³+] = mol/L Absorbance Iron(III) thiocynate standard curve 1.0 V 0.5 0.0001 Fe³+ concentration (M) 0 0.0002arrow_forwardThe intensity of red light (680 nm) and sorted by a solution of green dye was found to be 1.99 V and the intensity of light when no dye was present (the blank) was found to be 2.69 V.What is the absorbable of the solution of green dye in three significant figuresarrow_forward
- In an analytical laboratory a chemical compound namely Paracetamol (151.163 g/mol) is determined in a sample. A sample weighing 0.0295 g was dissolved in a solvent and diluted the solution to 1 L. The solution has λ max at 243 nm (ε=2.6×104 cm-1 mol-1 L). The solution exhibits an absorbance of 0.638 in a 2 cm cell. Calculate the percentage paracetamol in the sample.arrow_forward4. An ethanol solution of p-aminosalicylic acid has a molar absorptivity of 1.6 x 10ʻL mol"cm at a wavelength of 284 nm. Calculate the absorbance of a 4.8 x 10°M solution in a 1.000 cm cuvette at this wavelength.arrow_forwardWhat is the absorbance of a 2.33×10−4M2.33×10−4M solution of a compound with a molar absorptivity of 1.05×103M−1cm−11.05×103M−1cm−1 in a 1.00 cm cell?arrow_forward
- The absorbance of an unknown dye solution is measured to be 0.47 by a spectrometer. The linear equation of the spectrometer's calibration plot is y= 2156.5 x +0.0213, where y represents absorbance and x represents concentrations of dye. What is the molar concentration of the unknown sample (in mole L)? O2.08e4 O 2.08e-4 0 125e3 0 125e-3arrow_forwardA sample of drinking water is analyzed colorimetrically for ammonia nitrogen concentration. If the sample colour when viewed through a depth of 5.5 cm corresponds in intensity to a 1 mg/L standard sample when viewed through a depth of 40 cm, what is the concentration of ammonia nitrogen in the sample?arrow_forward(d) The Beer-Lambert law states that the absorbance (A) of light by a solution in a cuvette is given by: 10 A = In == ECL where lo is the incident light intensity, is the transmitted light intensity, e is the molar absorptivity, c is the concentration of the solution, and L is the path length of the cuvette. (1) Light with a wavelength of 800 nm is passed through a cuvette containing a solution of Coumarin dye. After passing through the cuvette, the light intensity was reduced to 10% of its initial value. What is the absorbance of the solution of Coumarin dye? (ii) The concentration of the Coumarin dye is 0.004 mol dm3, and the cuvette has a path length of 1 cm. What is the molar absorptivity of Coumarin dye at 800 nm, in units of m² mot¹? (IT) The molar absorptivity of Coumarin dye at 400 nm is three times larger than at 800 nm. How would the absorbance of the solution change, when measured with 400 nm light rather than 800 nm light?arrow_forward
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