Recent questions in Analytical Chemistry

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1 answer 34 views

A sample of unknown concentration of iron (Fe) is being analyzed using spectrophotometry. The absorbance values obtained from the analysis are: 0.3, 0.6, and 0.9. Using Beer's law, determine the concentration of iron in the sample.

asked Jan 22 in Analytical Chemistry by CarltonJjs44 (390 points)

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1 answer 47 views

A sample of drinking water from a local source was analyzed for its composition using mass balance calculations. The sample was found to contain 100 mg/L of calcium ions, 50 mg/L of magnesium ions, 20 mg/L of chloride ions, and 10 mg/L of sulfate ions. If the total volume of the sample was measured to be 50 mL, what is the mass of each ion present in the sample?

asked Jan 22 in Analytical Chemistry by DanieleKavel (290 points)

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1 answer 8 views

A sample of an unknown compound was analyzed using elemental analysis, and the results showed that the compound contains 12.8% hydrogen, 49.2% carbon, and 38.0% oxygen by mass. What is the empirical formula of the compound?

asked Jan 22 in Analytical Chemistry by WinstonU9990 (490 points)

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1 answer 56 views

A chemistry student was given a sample of an unknown compound. The student performed an analysis on the sample using mass balance calculations and obtained the following data: the sample had a mass of 2.64 g and contained 1.32 g of carbon, 0.22 g of hydrogen, and 0.88 g of oxygen. What is the molecular formula of the unknown compound?

asked Jan 22 in Analytical Chemistry by CharlotteBal (650 points)

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1 answer 55 views

A chemistry student was given a sample of a white crystalline substance, suspected to be a mixture of sodium chloride (NaCl) and potassium chloride (KCl). The student performed an analysis and found that the sample contained 64% chlorine by mass. Calculate the mass percentage of sodium chloride and potassium chloride present in the mixture.

asked Jan 22 in Analytical Chemistry by DarleneTudor (390 points)

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1 answer 4 views

A chemistry student wants to determine the percentage of ethanol in a sample of wine. The student takes a 50 mL aliquot of the wine, dries it, and finds the weight of the residual solids to be 0.325 g. The student then distills the rest of the wine, evaporates the distillate to dryness, and finds the weight of the residue to be 2.324 g. Using mass balance calculations, what is the percentage of ethanol in the wine sample?

asked Jan 22 in Analytical Chemistry by EssieHimes15 (350 points)

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1 answer 50 views

A chemistry student wants to determine the percent composition of calcium oxide in a given sample of limestone. The student does an experiment and obtains the mass of the limestone sample, the mass of carbon dioxide evolved upon heating the limestone, and the mass of calcium oxide left behind. Using mass balance calculations, determine the percent composition of calcium oxide in the limestone sample.

asked Jan 22 in Analytical Chemistry by MerriP79566 (510 points)

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1 answer 53 views

A chemistry student wants to determine the concentration of a solution containing iron (III) ions. Using colorimetry, they measure the absorbance of the solution at a specific wavelength and plot a calibration curve with solutions of known iron (III) ion concentration. The student then measures the absorbance of their unknown solution at the same wavelength and uses the calibration curve to determine the concentration of iron (III) ions in the sample. What is the concentration of iron (III) ions in the unknown solution, in units of moles per liter?

asked Jan 22 in Analytical Chemistry by GRXColleen50 (760 points)

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1 answer 66 views

A chemistry student wants to determine the amount of iron present in a sample of orange juice. The student takes a 50 mL sample of orange juice and reacts it with excess potassium dichromate in acidic solution. After the reaction, the remaining potassium dichromate requires 12.75 mL of a 0.015 M ferrous ammonium sulfate solution to complete the reaction. What is the mass of iron present in the sample of orange juice?

asked Jan 22 in Analytical Chemistry by GuadalupeDan (530 points)

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1 answer 71 views

A chemistry student wants to analyze a sample of wastewater from a local factory. They want to know the concentration of the pollutants from the wastewater before releasing it into the environment. The sample is collected in a 500 mL container. After performing the required tests, the student determines that the total dissolved solids (TDS) in the sample are 750 mg/L, and the concentration of NaCl in the sample is 150 mg/L. Calculate the mass of TDS and NaCl in the sample.

asked Jan 22 in Analytical Chemistry by JensKaye7769 (470 points)

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1 answer 64 views

A chemistry student needs to quantify the amount of iron (II) ions in a sample using colorimetry. The sample was prepared by dissolving a known mass of iron (II) sulfate in water, and the solution was diluted to a known volume. The student needs to determine the concentration of iron (II) ions in the original solution by measuring the absorbance of the sample using a colorimeter, and then using calibration curves to convert the absorbance to concentration. The student also needs to calculate the percentage error of the experiment and suggest ways to improve the accuracy of the results.

asked Jan 22 in Analytical Chemistry by PasqualePurv (680 points)

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1 answer 42 views

A chemistry student needs to identify an unknown compound using mass spectrometry. The compound has a molecular ion peak at m/z 120 and four major fragment ions at m/z 91, 77, 63, and 45. What is the molecular formula of the unknown compound?

asked Jan 22 in Analytical Chemistry by JennieCasas0 (470 points)

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1 answer 66 views

A chemistry student needs to identify an unknown compound found at a crime scene using mass spectrometry. The compound has a molecular weight of 286 g/mol and the mass spectrum shows a strong peak at m/z = 180 and a weaker peak at m/z = 148. What is the possible molecular formula of the unknown compound?

asked Jan 22 in Analytical Chemistry by ElaneLavarac (590 points)

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1 answer 8 views

A chemistry student needs to determine the pH of an unknown solution using a pH meter. The student is given the following equipment: pH meter, reference electrode, and a container for the solution. The student should describe the steps needed to measure the pH of the solution and explain the significance of the obtained pH value.

asked Jan 22 in Analytical Chemistry by KAULeora045 (510 points)

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1 answer 50 views

A chemistry student needs to determine the pH of a solution using a pH meter. The student has to prepare a buffer solution of pH 7.0 using 0.1M acetic acid and 0.1M sodium acetate. The student is then required to measure the pH of the prepared buffer solution using a pH meter and record the observations. Finally, the student has to compare the pH value obtained by the pH meter with the calculated pH value of the prepared buffer solution and explain any deviations observed.

asked Jan 22 in Analytical Chemistry by RomanCrh3176 (710 points)

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1 answer 46 views

A chemistry student needs to determine the percentage of iron (Fe) present in a given iron ore sample using gravimetric analysis. The student is provided with the mass of the iron ore sample and a standardized solution of potassium dichromate (K2Cr2O7) to use for the analysis. What is the percentage of iron (Fe) in the given iron ore sample?

asked Jan 22 in Analytical Chemistry by WiltonMayfie (790 points)

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1 answer 34 views

A chemistry student needs to determine the percentage of calcium carbonate (CaCO3) present in a mixture of calcium carbonate and calcium phosphate. The student has the following information: A 1.00-gram sample of the mixture was dissolved and reacted with excess hydrochloric acid (HCl), producing 0.236 grams of carbon dioxide (CO2) gas. The balanced chemical equation for the reaction is: CaCO3 + 2HCl → CaCl2 + CO2 + H2O. The student also knows that the molecular weight of CaCO3 is 100.09 g/mol and that of Ca3(PO4)2 is 310.18 g/mol. What is the percentage of calcium carbonate in the mixture?

asked Jan 22 in Analytical Chemistry by LolaSilas675 (370 points)

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1 answer 48 views

A chemistry student needs to determine the percent composition of nitrogen (N) in a sample of an unknown organic compound. Using elemental analysis, the student determines the mass of the sample to be 0.254 g and the mass of the products after combustion to be 0.727 g of CO2 and 0.298 g of H2O. What is the percent composition of nitrogen in the sample?

asked Jan 22 in Analytical Chemistry by ClaytonCavaz (570 points)

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1 answer 54 views

A chemistry student needs to determine the percent by mass of magnesium (Mg) in a sample of limestone. The student has access to 5 grams of the sample and is provided with the following information: the sample is comprised of calcium carbonate (CaCO3) and magnesium carbonate (MgCO3); the atomic masses of the elements are: Ca = 40.08 g/mol, C = 12.01 g/mol, O = 16.00 g/mol, and Mg = 24.31 g/mol; and the sample contains a total of 3.06 grams of carbon (C). Calculate the percentage by mass of magnesium in the limestone sample using mass balance calculations.

asked Jan 22 in Analytical Chemistry by ChiDunlop947 (370 points)

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1 answer 71 views

A chemistry student needs to determine the concentration of silver nitrate (AgNO3) in a given sample from the following information:- A 10 mL sample of 0.1 M sodium chloride (NaCl) was mixed with excess silver nitrate.- The resulting precipitate was filtered, washed, and dried. The mass of the precipitate was found to be 0.212 g.- The molar mass of AgNO3 is 169.87 g/mol.What is the concentration of AgNO3 in the original sample?

asked Jan 22 in Analytical Chemistry by MckinleyW743 (730 points)

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