Recent questions in Analytical Chemistry

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1 answer 114 views

An unknown compound was analyzed using mass spectrometry, and the resulting spectrum showed a molecular ion peak at m/z 214. Fragmentation patterns were also observed with peaks at m/z 121 and m/z 93. Can you identify the unknown compound and explain the fragmentation pathways leading to the observed peaks?

asked Jan 22 in Analytical Chemistry by VenusU65079 (1.8k points)

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1 answer 112 views

An unknown compound is synthesized in the lab and needs to be identified using mass spectrometry. Design a step-by-step plan to analyze the compound, including sample preparation, instrument settings, interpretation of data, and identification of possible functional groups.

asked Jan 22 in Analytical Chemistry by BrodieUus47 (1.7k points)

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1 answer 88 views

A student wants to determine the amount of chloride ions present in a sample of seawater. Using potentiometry, what is the concentration of chloride ions present in the sample?

asked Jan 22 in Analytical Chemistry by JoyEdge34400 (2.3k points)

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1 answer 261 views

A student wants to analyze the composition of a sample of an unknown metal alloy. They dissolve a 0.500g sample of the alloy in hydrochloric acid to form a solution which is then titrated with sodium hydroxide (NaOH) to neutralize the acid. The volume of the NaOH solution required is 16.50 mL. Assuming the acid reacts with the metal in the alloy according to the formula: M + 2HCl → MCl₂ + H₂, what is the percent composition by mass of Metal M in the alloy?

asked Jan 22 in Analytical Chemistry by Marilynn3793 (2.1k points)

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1 answer 179 views

A student received a sample of an unknown substance weighing 5 grams. After performing a series of measurements, they found that the sample contained 2.5 grams of pure calcium carbonate and an unknown amount of impurities. Using mass balance calculations, determine the weight and composition of the impurities in the sample.

asked Jan 22 in Analytical Chemistry by jozzaumnvuiyulg (2.5k points)

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1 answer 112 views

A student needs to determine the amount of copper present in a sample of brass using coulometry. If the sample is dissolved in acid and subjected to coulometric analysis using a standard silver electrode, what is the concentration of copper (in ppm) in the brass sample?

asked Jan 22 in Analytical Chemistry by MaybellHoffm (2.2k points)

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1 answer 132 views

A student needs to analyze an unknown sample to determine the percent composition of three compounds present in it. The student conducts a combustion reaction to determine the percent of carbon and hydrogen in the sample. The remaining residue is then dissolved in water and the solution is titrated with a standardized silver nitrate solution to determine the chloride ion concentration in the sample. Calculate the percent composition of each compound in the unknown sample using mass balance calculations.

asked Jan 22 in Analytical Chemistry by ErmelindaSey (1.8k points)

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1 answer 122 views

A student is given a mixture of two unknown substances, one organic and one inorganic, and is asked to identify these compounds using mass spectrometry. Can you provide a step-by-step procedure using mass spectrometry to identify the two unknown compounds?

asked Jan 22 in Analytical Chemistry by RichieRedric (1.9k points)

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1 answer 77 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 LavadaKissne (2.4k points)

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1 answer 148 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 HughNewquist (2.3k points)

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1 answer 77 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 HermineOverb (2.1k points)

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1 answer 105 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 RobynButz517 (1.9k points)

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1 answer 173 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 NorineFelici (1.8k points)

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1 answer 85 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 DoloresLocke (1.7k points)

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1 answer 121 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 EnriquetaDam (2.3k points)

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1 answer 167 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 IolaHolly818 (2.0k points)

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1 answer 132 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 SantoSutclif (1.4k points)

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1 answer 178 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 ShaunBehan45 (2.8k points)

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1 answer 130 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 RobertoLafla (2.1k points)

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1 answer 78 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 Ben56061281 (1.4k points)

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