2. To spectrophotometrically determine the mass percent of cobalt in an ore containing cobalt and some inert materials, solutions with known [Co2+] are prepared and the absorbance of each of the solutions is measured at the wavelength of optimum absorbance. The data are used to create a calibration plot, shown below. Absorbance 0.90- 0.80- 0.70- 0.60- 0.50 0.40- 0.30- 0.20- 0.10- 0.00++ 0 0.005 0.0103 0.015 Concentration (M) .04. A 0.630 g sample of the ore is completely dissolved in concentrated HNO3(aq). The mixture is diluted with water to a final volume of 50.00 mL. Assume that all the cobalt in the ore sample is converted to Co²+ (aq). (a) What is the [Co2+] in the solution if the absorbance of a sample of the solution is 0.74 ? (b) Calculate the number of moles of Co²+ (aq) in the 50.00 mL solution. (c) Calculate the mass percent of Co in the 0.630 g sample of the ore.

If the solution #1 has an absorbance of 0.219 at equilibrium, calculate the [Fe(SCN)2+] in the solution using the line equation y=3189x-0.03392

Potentially Useful Information Spectrochemical Series: | < Br < SCN < Cl° < NO3¯< F° < OH° < C2O4²- ~ H2O < NCS < NH3 < en < PPH3 A student synthesizes and isolates the following coordination compound [Ni(H2NCH2CH2NH2)3]Cl2 (molar mass = 309.8966 g/mol) according to the balanced reaction below. In the experiment, the student reacts 2.500 g of nickel (II) chloride hexahydrate (molar mass = 237.6878 g/mol) with 4.000 g of ethylenediamine (molar mass = 60.0992 g/mol). After isolating the product, the student collects 3.200 g of the nickel coordination compound. NICI2•6H2O (aq) + 3H2NCH2CH2NH2 (1) → [Ni(H2NCH2CH2NH2)3]Cl2 (s) + 6H2O (1) Given the transition metal compound, Na4[Co(C204) (CN)4], what is the oxidation state of cobalt, as well as the coordination number of cobalt in this compound? This compound is soluble in water. The oxidation state of cobalt is Cobalt has a coordination number of Your answer should be an integer.

Ligand X forms a complex with both cobalt and copper, each of which has a maximum absorbance at 510 nm and 645 nm. respectively. A 0.243 g sample containing cobalt and copper was dissolved and diluted to a volume of 100.0 mL. A solution containing ligand X was added to a 50.0 mL aliquot of the sample solution and diluted to a final volume of 100.0 mL. The measured absorbance of the unknown solution was 0.503 at 510 nm and 0.368 at 645 nm, when measured with a 1.00 cm cell. The molar absorptivities of the cobalt and copper complexes at each wavelength are shown in the table. Molar Absorptivity (c. M-'cm-¹) Wavelength [Co² = A, nm [Cu²+] = 510 645 3.125 x10-5 Incorrect Co 2.867 x10-5 3.7630 x 10² What is the concentration of cobalt and copper in the final diluted solution? 1282 Cu 5707 18090 M M

The absorbance of iron is determined at 508 nm. From the information given in the laboratory handout, what do you think the visible absorption spectrum of the iron complex [Fe(phen)3]2+ looks like?

A sample of an iron ore was prepared for Fe3+ analysis as following: 3.4g of the sample was added anddissolved in acid environment then diluted to 250 mL using volumetric flask. After that, 10 mL of the resultingsolution was transferred by pipet to a 50-mL volumetric flask and continue to be diluted. The scientists foundout that this solution gives the concentration of Fe3+ as 2.3 mg/L. Find the weight percentage of Fe3+ in theoriginal sample.

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