4. Two technicians have analyzed a standard with a known nitrate concentration of 25.0 mg/L. TH results are shown below. Trial 1 2 5 Results from Technician 1 (mg/mL) Results from Technician 2 (mg/mL) 23.8 23.4 23.2 23.4 22.9 23.6 Average: 23.4 30.1 22.4 27.5 21.3 Average: 24.9 Choose the statement below which is FALSE. a. Technician 2 has greater accuracy than technician 1. b. Technician 1 has greater precision than technician 2. c. Results from technician 1 have both systematic and random error. d. Results from technician 2 only have determinant error.

4. Two technicians have analyzed a standard with a known nitrate concentration of 25.0 mg/L. TH results are shown below. Trial 1 2 5 Results from Technician 1 (mg/mL) Results from Technician 2 (mg/mL) 23.8 23.4 23.2 23.4 22.9 23.6 Average: 23.4 30.1 22.4 27.5 21.3 Average: 24.9 Choose the statement below which is FALSE. a. Technician 2 has greater accuracy than technician 1. b. Technician 1 has greater precision than technician 2. c. Results from technician 1 have both systematic and random error. d. Results from technician 2 only have determinant error.

Appl Of Ms Excel In Analytical Chemistry

2nd Edition

ISBN:9781285686691

Author:Crouch

Publisher:Crouch

Chapter14: Chromatography

Section: Chapter Questions

Problem 9P

See similar textbooks

Similar questions

If an instrument gives a response of 1240 for a standard containing 8 ppm of a substance, how much if this substance is in a sample that gives a response of 1705? Are any assumptions needed?
A solution of Ca(OH)2 (FM = 74.09) was used in determining the equivalent weight of an unknown acid. To do so, the said solution was standardized against 0.1235 g KHP (FM = 204.22), requiring 7.45 mL to reach the phenolphthalein endpoint. On the other hand, a 0.0543 g unknown acid requires 12.85 mL standard Ca(OH)2 to reach the desired endpoint.a. Calculate the standard normality of Ca(OH)2.b. Calculate the equivalent weight of the unknown acid.c. From the information in the table, what is the most probable identity of the unknown acid?
You determine the acetic acid (HOAc) content of vinegar by titrating with a sodium hydroxide standard solution to a phenolphthalein (an indicator) end point. An approximately 5-mL sample of vinegar is weighed on an analytical balance in a weighing boat and this is found to be 5.0268 g. The standard deviation in making a single weighing is 0.2 mg. The sodium hydroxide must be accurately standardised (this means its concentration must be accurately determined) by titrating known mass of high-purity potassium hydrogen phthalate, and three such titrations give molar concentrations of 0.1167, 0.1163 and 0.1164 mol L-1. A volume of 36.78 mL of sodium hydroxide is used to titrate each sample. The standard deviation of the burette used is 0.02 mL. Calculate the percentage of acetic acid in the vinegar and its standard deviation.
Standardization of Sodium Thiosulfate Solution Primary Standard used: Potassium Dichromate Formula mass of 1o standard: __________________ % Purity of 1o standard: 99.80% Trials 1 2 3 Weight of K2Cr2O7 (g)Weight of K2Cr2O7 (g) 0.0315 0.0331 0.0380 Final Volume Reading Na2S2O3 (ml) 27.50 27.50 34.90 Initial Volume Reading Na2S2O3 (ml) 1.10 0.00 1.00 Net Volume Na2S2O3 used (ml) Molarity of Na2S2O3
SCE students measured the concentration of HCl in a solution by titrating with different indicators to find the end point.Indicator Mean HCl concentration (M)(± standard deviation)Number of measurementsBromothymol blue 0.09565 ± 0.00225 28Methyl red 0.08686 ± 0.00098 18Bromocresol green 0.08641 ± 0.00113 29Is the difference between indicators 1 and 2 significant at the 95% confidence level? Answer the same question for indicators 2 and 3
The thiourea in a 1.455 g sample of organic material was extracted into a dilute sulfuric acid solution and titrated with 37.31 mL of 0.009372 M Hg2+ via reaction: 4(NH2)2CS + Hg2+ →[(NH2)2CS]4 Hg2+ P.S. Answer only the last two letters of the following questions. (Only C and D) a. Is this an example of total analysis technique or concentration technique? Explain. b. Calculate the percent (NH2)2CS ( 76.12 g/mol) in the sample. c. What is classification of the analysis based on the amount of sample and amount of analytes present? Explain. d. If the true value is 10.00%, calculate the absolute and relative error.
A 25.00mL wastewater sample was analyzed for its Mg2+ content using a standard gravimetric method. the sample was diluted to 3.00L and an 11.00mL aliquot was treated to precipitate magnesium as MgNH4PO4.6H2O using (NH4)2HPO4 as the precipitating agent. the precipitate was then filtered, washed, dried, and ignited resulting in a 0.1325mg Mg2P2O7 residue. How much Mg (in ppm) is present in the original sample
A 50.00 (±0.03) mL portion of an HCl solution required 29.71(±0.03) mL of 0.01963(±0.0030) M Ba(OH)2 to reach an end point with bromocresol green indicator. The molar concentration of the HCl is calculated using the equation below (attached image): a.) Calculate the uncertainty of the result (absolute error). M=0.02333(±?????) M b.) Calculate the coefficient of variation for the result. CV= (Sy/y) x 100%
125.1 mg of streptomycin sulphate are dissolved in 10 ml of water. A GC headspace analysis is carried out in order to determine the methanol content of the drug. A peak for methanol is produced which has 73.2% of the area of a peak for a methanol standard containing 0.532 mg/100 ml of methanol in water analysed under exactly the same conditions, What is the methanol content of the streptomycin sulphate in ppm and %w/w? Answer: 311.3 ppm, 0.3113 % w/w.how??
If exactly 200.0 mL of an aqueous solution that is 1.037E3 ppb Pb(NO3)2 (331.2 g/mol) is mixed with 100.0 mL of an aqueous solution that is 3.090E9 fM KI (166.00 g/mol), how many micrograms of solid PbI2 (461.01 g/mol, 6.16 g/mL) are formed? Assume complete reaction.
The analysis shows different concentrations based on replicate determinations of Zn in a water sample: 0.754 mg, 0.721 mg, 0.734 mg, 0.731 mg and 0.742 mg. What is the absolute error if the standard solution has 0.750 mg of Zn?
Using the percent purity calculations, determine the percent yield of synthesis of aspirin. Part I Synthesis of Aspirin Mass of salicylic acid used (g) 2.029g Volume of acetic anhydride used (mL) 5ml Mass of acetic anhydride used (vol. × 1.08 g/mL) 5.4g Mass of aspirin synthesized (g) 3.256g Part II Melting Temperature Data Melting temperature (°C) 133°C Part III Salicylic Acid Standard Stock Solution Initial mass of salicylic acid (g) 0.210g Moles of salicylic acid (mol) 0.0147 mol Initial molarity of salicylic acid (M) 0.724 M Part III Beer’s Law Data for Salicylic Acid Standard Solutions Trial Concentration (M) Absorbance Water (mL) 1 10 0.301 0 2 7.5 0.219 2.5 3 5.0 0.163 5.0 4 2.5 0.074 7.5 Best-fit line equation for the salicylic acid standards Test of the Purity of the Synthesized Aspirin Initial mass of aliquot of product (g)…