A sample of an alum was analysed by atomic spectroscopy and gravimetrically to determine its structure. A 0.1000 g of the sample when treated with BaCl₂ produced 0.0984 g of a white solid after drying to constant weight. Another 0.1000 g sample of the alum when heated at 105°C for several hours produced a weight loss of 0.04558 g while the % of K in the sample was determined by atomic spectroscopy to be 8.240%. Use these results to work out a formula for the alum. [M,/ g mole¹: K 39.10; Al 26.98; BaSO, 233.39; SO² 96.06; H₂O 18.0148]

A sample of an alum was analysed by atomic spectroscopy and gravimetrically to determine its structure. A 0.1000 g of the sample when treated with BaCl₂ produced 0.0984 g of a white solid after drying to constant weight. Another 0.1000 g sample of the alum when heated at 105°C for several hours produced a weight loss of 0.04558 g while the % of K in the sample was determined by atomic spectroscopy to be 8.240%. Use these results to work out a formula for the alum. [M,/ g mole¹: K 39.10; Al 26.98; BaSO, 233.39; SO² 96.06; H₂O 18.0148]

Fundamentals Of Analytical Chemistry

9th Edition

ISBN:9781285640686

Author:Skoog

Publisher:Skoog

Chapter12: Gravimetric Methods Of Analysis

Section: Chapter Questions

Problem 12.6QAP

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g. Aluminium in 1.200 g sample of impure ammonium aluminium sulphate was precipitated with aqueous ammonia as the hydrous Al2O3.xH2O. The precipitate was filtered and ignited at 1000 °C to give anhydrous Al2O3 which weighed 0.1798 g. Calculate the percentage of aluminium in the sample (Atomic weight Al= 26.98 g mol-1; Molecular weight Al2O3 = 101.96 g mol-1).
2. An iron ore was analyzed by dissolving a 1.1324 g sample in concentrated HC. The resulting solution was diluted with water, and the iron(III) was precipitated as hydrous oxide Fe,03 .XH20 by the addition of NH3. After filtration and washing, the residue was ignited at a high temperature to give 0.5394 g of pure Fe,03 (FW = 159.69). Calculate (a) the percent Fe (FW = 55.847) and (b) the percent Fe;04 (FW = 231.54) in the sample.
The digestion of a 0.1159 gram sample of a phosphorous-containing compound in a mixture of HNO3 and H2SO4 resulted in the formation of CO2, H2O, and H3PO4. Addition of ammonium molybdate yielded a solid having the composition (NH4)3PO4·12MoO3 (FW = 1876.3). This precipitate was filtered, washed, and dissolved in 50.00 mL of 0.2000 M NaOH: (NH4)3PO4•12MoO3(s)+26OH-(aq)->HPO42-(aq)+12MoO42-(aq)+14H2O(l)+3NH3(g) After the solution was boiled to remove the NH3, the excess NaOH was back-titrated with 14.84 mL of 0.1626 M HCl to a phenolphthalein end point. Calculate the percent phosphorous (FW = 30.9737) in the sample.
A standard iron solution was prepared by dissolving 0.0140 g of pure iron in acid then transferring to a 50.00 mL volumetric flask with orthophenanthroline as a complexing agent. At a wavelength of 540 nm, the absorbance of the standard was 0.214 in a 1.00 cm cuvette. A 0.128 g sample of an iron ore was crushed and digested in 5 mL of concentrated acid. The digested sample was then transferred to a 10.00 mL volumetric flask and diluted to the mark with water. A 1.00 mL aliquot of the sample was transferred to a 25.00 mL volumetric flask, and diluted to the mark with water. A portion of the diluted sample was then transferred to a 1.00 cm cuvette and measured at a wavelength of 540 nm. The resulting absorbance was 0.216. Determine the % w/w of Fe in the iron ore.
25.0 g of an impure sample containing cobalt was dissolved in acid and diluted to1000.00 mL. 6.00 mL of this sample was removed, treated appropriately to give a coloredsolution, and then diluted to 250.00 mL. This final solution had an absorbance of 0.410.Calculate the percentage of cobalt (MW = 58.93 g/mol) in the original sample.
Caustic potash that has been exposed to air is found on analysis to contain 90.00% KOH, 2.38% K2CO3 and 7.62% H2O. What weight of residue will be obtained if 1.00 g of this sample is added to 46.00 mL of 1.00 N HCl and the resulting solution, after neutralization with 1.070N KOH is evaporated to dryness?
Use the following atomic masses (in g/mol): Mg = 24.31; O = 16; Ca = 40.08; C = 12.01; Na = 23; H = 1; N = 14.01; S = 32.06; Cl = 35.45; 1.) Calculate the MgO content of 12.35g Magnesia Magma, which has been dissolved in 50mL of 1.0340N H2SO4 and required 24.6mL of 1.1255N NaOH in the back titration.
A 0.951-g sample containing (NH4)2C2O4 and compounds was dissolved in water and made alkaline with KOH. The liberated ammonia was distilled into 50.00 mL of 0.1007 N H2SO4. The excess H2SO4 was back titrated with 11.13 mL of 0.1214 N NaOH. Calculate the percentage of nitrogen in the sample.
2. Explain the principle of ion exchange adsorption.
Explain why the energetics of dissolution can be different for elements in the same group?
4. Limestone containing 87% CaCO3, 6% MgCO3, 3% hematite, 2% silica and remaining water is calcined in hot water to vaporize the water and separate CO2 from the carbonates. The CaO and MgO created by the reaction leave in the solid calcine, along with hematite and silica. How many kilograms of calcine will be produced per ton of limestone?
0.0123 g of the powder from the tablet ( 1.4770g) was transferred to a 100 mL volumetric flask. 20 mL of 1M hydrochloric acid was added to the flask. The volume in the flask was then made up to the mark with deionized water which was filtered. 40 mL of the filtrate and 4 mL of a lanthanum chloride solution were placed into a large test tube. Half of the prepared sample was spiked with a 20 mg/L calcium standard. The calibration standards and the unknown sample solutions were then measured for calcium concentration at 422.7 nm with flame atomic absorption spectroscopy. Each tablet is stated by the manufacturer to contain 500 mg of calcium. Sample ID Absorbance Blank 0.039Reagent Blank 0.194Sample 0.855Spiked sample 1.184Calibration curve: y = 0.0184x + 0.007; r2 = 0.991 Calculate the spike recovery for the calcium analysis.