A dilute solution of an unknown weak acid required a 28.94-mL titration with 0.1062 M NaOH to reach a phenolphthalein end point. The titrated solution was evaporated to dryness. Calculate the equivalent mass of the acid if the sodium salt was found to weigh 0.2110 g.
> An EDTA solution was prepared by dissolving 3.426 g of purified and dried Na2H2Y · 2H2O in sufficient water to give 1.000 L. Calculate the molar concentration, given that the solute contained 0.3% excess moisture (see Section 15D-1).
> Why is a small amount of MgY2− often added to a water specimen that is to be titrated for hardness?
> The sulfate ion concentration in natural water can be determined by measuring the turbidity that results when an excess of BaCl2 is added to a measured quantity of the sample. A turbidimeter, the instrument used for this analysis, was calibrated with a s
> Given an overall complex formation reaction of with an overall formation constant of βn, show that the following relationship holds:
> Propose a complexometric method for the determination of the individual components in a solution containing
> Write a conditional overall formation constant for [Fe(Ox)3] 3− in terms of α2 for oxalic acid and the β value for the complex. Also express the conditional constant in terms of concentrations as in Equation 15-20.
> Write conditional formation constants for 1:1 complexes of Al(III) with each of the ligands in Problem 15-11. Express these constants in terms of the α value and the formation constant and in terms of concentrations as in Equation 15-20.
> Write equations in terms of the acid dissociation constants and [H+] for the highest alpha value for each of the following weak acid ligands:
> The phosphorus in a 0.3019-g sample was precipitated as the slightly soluble 1NH423PO4 . 12MoO3. This precipitate was filtered, washed, and then redissolved in acid. Treatment of the resulting solution with an excess of Pb21 resulted in the formation of
> Convert the following p-functions to molar concentrations: a. pH = 1.102. b. pOH = 0.0057. c. pBr = 7.77. d. pCa = -0.221. e. pLi = 12.35. f. pNO3 = 0.054. g. pMn = 0.135. h. pCl = 8.92.
> What is the difference between molar species concentration and molar analytical concentration?
> Outline a method for the determination of K+ based on argentometry. Write balanced equations for the chemical reactions.
> Outline a method for the determination of K+ based on argentometry. Write balanced equations for the chemical reactions.
> Why does the charge on the surface of precipitate particles change sign at the equivalence point of a titration?
> A method for the determination of the corticosteroid methylprednisolone acetate in solutions obtained from pharmaceutical preparations yielded a mean value of 3.7 mg mL-1with a standard deviation of 0.3 mg mL-1. For quality control purposes, the relative
> Briefly explain why the sparingly soluble product must be removed by filtration before you back-titrate the excess silver ion in the Volhard determination of
> Give two reasons why ( ( 3 2 KH IO is preferred over benzoic acid as a primary standard for a 0.010 M NaOH solution.
> Why is it common practice to boil the solution near the equivalence point in the standardization of Na2CO3 with acid?
> The boiling points of HCl and CO2 are nearly the same (285°C and 278°C). Explain why CO2 can be removed from an aqueous solution by boiling briefly while essentially no HCl is lost even after boiling for 1 hour or more.
> Four analysts perform replicate sets of Hg determinations on the same analytical sample. The results in ppb Hg are shown in the following table: a. State the appropriate hypotheses. b. Do the analysts differ at the 95% confidence level? At the 99% confi
> Describe how Na2CO3 of primary-standard grade can be prepared from primary-standard NaHCO3.
> Why is nitric acid seldom used to prepare standard acid solutions?
> A 10.00-mL sample of vinegar (acetic acid, CH3COOH) was pipetted into a flask, two drops of phenolphthalein indicator were added, and the acid was titrated with 0.1008 M NaOH a. If 45.62 mL of the base was required for the titration, what was the molar c
> At 25°C, what are the molar H3O1 and OH2 concentrations in a. 0.0300 M HCOOH? b. 0.0600 M HN3? c. 0.200 M ethylamine? d. 0.100 M trimethylamine? e. 0.250 M C6H5COONa (sodium benzoate)? f. 0.0750 M CH3CH2COONa? g. 0.250 M hydroxylamine hydrochloride? h. 0
> Calculate the equivalent mass of oxalic acid dehydrateH2C2O4 2H2O,12066g/mol when it is titrated to (a) a bromocresol green end point and (b) a phenolphthalein end point.
> Define the equivalent mass of (a) an acid and (b) a base
> The seller of a mining claim took a random ore sample that weighed approximately 5 lb and had an average particle diameter of 5.0 mm. Inspection revealed that about 1% of the sample was argentite (see Problem 6-9), and the remainder had a density of abou
> How did the definition of the mole change with the 2019 redefinition of SI base units?
> A series of solutions containing NaOH,Na2CO3 , and NaHCO3 , alone or in compatible combination, was titrated with 0.1202 M HCl. In the following table are the volumes of acid needed to titrate 25.00-mL portions of each solution to (1) a phenolphthalein a
> A series of solutions containing NaOH,Na3AsO4 , and Na2HAsO4 , alone or in compatible combination, was titrated with 0.08601 M HCl. In the following table are the volumes of acid needed to titrate 25.00-mL portions of each solution to (1) a phenolphthale
> A 0.6407-g sample containing chloride and iodide ions gave a silver halide precipitate weighing 0.4430 g. This precipitate was then strongly heated in a stream of Cl2 gas to convert the AgI to AgCl; on completion of this treatment, the precipitate weighe
> Calculate the volume of 0.07731 M NaOH needed to titrate a. 25.00 mL of a solution that is 0.03000 M in HCl and 0.01000 M in H3PO4 to a bromocresol green end point. b. the solution in (a) to a thymolphthalein end point. c. 30.00 mL of 006407MNaH 2PO
> Calculate the volume of 0.06452 M HCl needed to titrate a. 20.00 mL of 005522MNa3PO4 to a thymolphthalein end point. b. 25.00 mL of 005522MNa3PO4 to a bromocresol green end point. c. 40.00 mL of a solution that is 0.02199 M in Na3PO4 and 0.01714
> A 0.5000-g sample containing NaHCO3 , Na2CO3 , and H2O was dissolved and diluted to 250.0 mL. A 25.00-mL aliquot was then boiled with 50.00 mL of 0.01255 M HCl. After cooling, the excess acid in the solution required 2.34 mL of 0.01063 M NaOH when titra
> A 1.421-g sample of commercial KOH contaminated by K2CO3 was dissolved in water, and the resulting solution was diluted to 500.0 mL. A 50.00-mL aliquot of this solution was treated with 40.00 mL of 0.05567 M HCl and boiled to remove CO2 The excess acid
> A 1.219-g sample containing (NH4)2SO4, NH4NO3, and nonreactive substances was diluted to 200 mL in a volumetric flask. A 50.00-mL aliquot was made basic with strong alkali, and the liberated NH3 was distilled into 30.00 mL of 0.08421 M HCl. The excess HC
> A 0.8835-g sample of a wheat flour was analyzed by the Kjeldahl procedure. The ammonia formed was distilled into 50.00 mL of 0.05078 M HCl; a 8.04-mL back-titration with 0.04829 M NaOH was required. Calculate the percentage of protein in the flour.
> Calculate the p-functions for each ion in a solution that is A. 0.0200 M in NaBr. b. 0.0300 M in BaBr2. c. 4.5 × 10-3 M in Ba(OH)2. d. 0.020 M in HCl and 0.010 M in NaCl. e. 7.2 × 10-3 M in CaCl2 and 8.2 × 10-3 M in BaCl2. f. 2.8 × 10-8 M in Zn(NO3)2
> A 0.5843-g sample of a plant food preparation was analyzed for its N content by the Kjeldahl method, the liberated NH3 being collected in 50.00 mL of 0.1062 M HCl. The excess acid required an 11.89 mL back-titration with 0.0925 M NaOH. Express the result
> The data in the accompanying table represent the concentration of glucose in the blood serum of an adult patient. On four consecutive days, a blood sample was drawn from the patient and analyzed in triplicate. The variance for a given sample is an estima
> Calculate the mass in grams of protein in a 5.00-oz can of tuna in Problem 14-35.
> A 0.7891-g sample of a mixture consisting solely of sodium bromide and potassium bromide yields 1.2895 g of silver bromide. What are the percentages of the two salts in the sample?
> A 0.917-g sample of canned tuna was analyzed by the Kjeldahl method. A volume of 20.59 mL of 0.1249 M HCl was required to titrate the liberated ammonia. Calculate the percentage of nitrogen in the sample.
> The Merck Index indicates that 10 mg of guanidine, CHN53 , may be administered for each kilogram of body mass in the treatment of myasthenia gravis. The nitrogen in a 4-tablet sample that had a total mass of 7.66 g was converted to ammonia by a Kjeldahl
> Neohetramine, C16H22ON428637g/mol, is a common antihistamine. A 0.1247-g sample containing this compound was analyzed by the Kjeldahl method. The ammonia produced was collected in H3BO3 ; the resulting HBO2 3 was titrated with 26.13 mL of 0.01477 M
> A 0.9826-g sample containing dimethyl phthalate, C6H4COOCH3 219419g/mol, and unreactive species was refluxed with 50.00 mL of 0.1104 M NaOH to hydrolyze the ester groups (this process is called saponification). C6H4 COOCH3 2 2OHC6H4 COO2
> The digestion of a 0.1417-g sample of a phosphorus-containing compound in a mixture of HNO3 and H2SO4 resulted in the formation of CO2 ,H2O, and HPO34 Addition of ammonium molybdate yielded a solid having the composition NH43 PO4 12MoO318763g/
> Air was bubbled at a rate of 30.0 L/min through a trap containing 75 mL of 1% H2O2 H2O2 SO2 H2SO4 After 10.0 minutes, the H2SO4 was titrated with 10.95 mL of 0.00242 M NaOH. Calculate concentration of SO2 in parts per million (that is, mLSO2 106m
> A 3.00-L sample of urban air was bubbled through a solution containing 50.0 mL of 00116MBaOH2 , which caused the CO2 in the sample to precipitate as BaCO3 The excess base was back-titrated to a phenolphthalein end point with 23.6 mL of 0.0108 M HC
> Calculate the pH of water at 25°C and 50°C. The values for pKw at these temperatures are 13.99 and 13.26, respectively.
> In the determination of lead in a paint sample, it is known that the sampling variance is 10 ppm while the measurement variance is 4 ppm. Two different sampling schemes are under consideration: Scheme a: Take five sample increments and blend them. Perfor
> The efficiency of a particular catalyst is highly dependent on its zirconium content. The starting material for this preparation is received in batches that assay between 68% and 84% ZrCl4. Routine analysis based on precipitation of AgCl is feasible, it
> The aluminum in a 2.200-g sample of impure ammonium aluminumsulfate 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 0.3006 g. Express the result o
> A 0.1401-g sample of a purified carbonate was dissolved in 50.00 mL of 0.1140 M HCl and boiled to eliminate CO2 Back-titration of the excess HCl required 24.21 mL of
> A 25.00-mL sample of a household cleaning solution was diluted to 250.0 mL in a volumetric flask. A 50.00-mL aliquot of this solution required 43.04 mL of 0.1776 M HCl to reach a bromocresol green end point. Calculate the mass/volume percentage of NH3 in
> The active ingredient in Antabuse, a drug used for the treatment of chronic alcoholism, is tetraethylthiuram disulfide, (296.54 g/mol). The sulfur in a 0.4169-g sample of an Antabuse preparation was oxidized to SO2 , which was absorbed in H2O2 to give H2
> The benzoic acid extracted from 86.7 g of catsup required a 15.61-mL titration with 0.0654 M NaOH. Express the results of this analysis in terms of percent sodium benzoate (144.10 g/mol).
> The formaldehyde (HCHO) content of a pesticide preparation was determined by weighing 0.2985 g of the liquid sample into a flask containing 50.0 mL of 0.0959 M NaOH and 50 mL of 3% H2O2Upon heating, the following reaction took place: OHHCHOH2O2 H
> A 0.7041-g sample of impure mercury(II) oxide was dissolved in an unmeasured excess of potassium iodide. Reaction: HgOs4IH2OHgI242OH Calculate the percentage of HgO in the sample if titration of the liberated hydroxide required 40.67 mL of
> Titration of a 0.7513-g sample of impure Na2B4O7 required 30.79 mL of 0.1129 M HCl (see Problem 14-16f for reaction). Express the results of this analysis in terms of percent a. Na2B4O7 b. Na2B4O7 10H2O c. B2O3 d. B.
> A 25.0-mL aliquot of vinegar was diluted to 250 mL in a volumetric flask. Titration of 50.0mL aliquots of the diluted solution required an average of 25.23 mL of 0.09041 M NaOH. Express the acidity of the vinegar in terms of the percentage (w/v) of aceti
> A 50.00-mL sample of a white dinner wine required 24.57 mL of 0.03291 M NaOH to achieve a phenolphthalein end point. Express the acidity of the wine in grams of tartaric acid H2C4H4O6 ;15009g/mol per 100 mL. (Assume that two hydrogens of the acid ar
> a. Compare the masses of potassium hydrogen phthalate (204.22 g/mol), potassium hydrogen iodate (389.91 g/mol), and benzoic acid (122.12 g/mol) needed for a 50.00-mL standardization of 0.0600 M NaOH. b. What would be the relative standard deviation in t
> The addition of dimethylglyoxime, H2C4H6O2N2, to a solution containing nickel(II) ion gives rise to a precipitate: Nickel dimethylglyoxime is a bulky precipitate that is inconvenient to manipulate in amounts greater than 175 mg. The amount of nickel in a
> Approximately 15% of the particles in a shipment of silver-bearing ore are judged to be argentite, Ag2S (d = 7.3 g cm-3, 87% Ag); the remainder are siliceous (d = 2.6 g cm-3) and contain essentially no silver. a. Calculate the number of particles that sh
> Calculate the molar H3O+ ion concentration of a solution that has a pH of a. 3.73. b. 3.28. c. 0.59. d. 11.29. e. 7.62. f. 5.19. g. -0.76. h. -0.42.
> Calculate the relative standard deviation in the computed molar concentration of 0.0200 M HCl if this acid was standardized against the masses found in Example 14-1 for (a) TRIS, (b) Na2CO3 , and (c) Na2B4O7 10H2O Assume that the absolute standard devi
> Suggest a range of sample masses for the indicated primary standard if it is desired to use between 35 and 45 mL of titrant a. 0.180 M HClO4 titrated against Na2CO3(CO2 product) b. 0.102 M HCl titrated against Na2C2O4 c. 0.180 M NaOH titrated against ben
> Calculate the molar concentration of a dilute BaOH2 solution if a. 50.00 mL yielded 0.1791 g of BaSO4 b. titration of 0.4512 g of primary-standard potassium hydrogen phthalate (KHP) required 26.46 mL of the base c. addition of 50.00 mL of the base to 0
> Calculate the molar concentration of a dilute HCl solution if a. A 50.00-ml aliquot yielded 0.6027 g of agcl. b. The titration of 25.00 ml of 004096mbaOH2 required 17.93 ml of the acid c. The titration of 0.2407 g of primary-standard Na2CO3 requir
> A NaOH solution was 0.1019 M immediately after standardization. Exactly 500.0 mL of the reagent was left exposed to air for several days and absorbed 0.652 g of CO2 Calculate the relative carbonate error in the determination of acetic acid with this so
> If 1.000 L of 0.2000 M NaOH was unprotected from the air after standardization and absorbed 14.2 mmol of CO2 , what is its new molar concentration when it is standardized against a standard solution of HCl using
> The concentration of a perchloric acid solution was established by titration against primary-standard sodium carbonate (product: CO2 ); the following data were obtained.
> Standardization of a sodium hydroxide solution against potassium hydrogen phthalate (KHP) yielded the results in the following table. a. the average molar concentration of the base. b. the standard deviation and the coefficient of variation for the dat
> A series of sulfate samples is to be analyzed by precipitation as BaSO4. If it is known that the sulfate content in these samples ranges between 20% and 55%, what minimum sample mass should be taken to ensure that a precipitate mass no smaller than 0.200
> How would you prepare 2.00 L of a. 0.10 M KOH from the solid? b. 0010MBaOH2 8H2O from the solid? c. 0.150 M HCl from a reagent that has a density of 1.0579 g/mL and is 11.50% HCl (w/w)?
> The mishandling of a shipping container loaded with 850 cases of wine caused some of the bottles to break. An insurance adjuster proposed to settle the claim at 20.8% of the value of the shipment, based on a random 250-bottle sample in which 52 were crac
> How would you prepare 500 mL of a. 0100MHSO24 from a reagent that has a density of 1.1539 g/mL and is 21.8% H2SO4w/w? b. 0.200 M NaOH from the solid? c. 008000MNa2CO3 from the pure solid?
> The solubility products for a series of hydroxides are Which hydroxide has a. the lowest molar solubility in H2O? b. the lowest molar solubility in a solution that is 0.35 M in NaOH?
> Briefly describe the circumstance where the concentration of a sodium hydroxide solution will apparently be unaffected by the absorption of carbon dioxide.
> What types of organic nitrogen-containing compounds tend to yield low results with the Kjeldahl method unless special precautions are taken?
> Suggest an indicator that could be used to provide an end point for the titration of the first proton in H3AsO4.
> Indicate whether an aqueous solution of the following compounds is acidic, neutral, or basic. Explain your answer. a. NaH2PO4 b. Na3PO4 c. NaNO3 d. NaHC2O4 e. Na2C2O4 f. Na2HPO4 g. NH4OAc h. NaNO2
> Why is it impossible to titrate all three protons of phosphoric acid in aqueous solution?
> Briefly explain why Equation 13-15 can only be used to calculate the hydronium ion concentration of solutions in which NaHA is the only solute that determines the pH.
> Find the number of millimoles of solute in a. 2.00 L of 0.0449 M KMnO4. b. 750 mL of 5.35 × 10-3 M KSCN. c. 3.50 L of a solution that contains 6.23 ppm of CuSO4. d. 250 mL of 0.414 mM KCl.
> Explain the origin and significance of each of the terms on the right side of Equation 13-12. Does the equation make intuitive sense? Why or why not?
> As its name implies, NaHA is an “acid salt” because it has a proton available to donate to a base. Briefly explain why a pH calculation for a solution of NaHA differs from that for a weak acid of the type HA.
> Find the number of Na+ ions in 2.75 g of Na3PO4?
> Calculate alpha values for the following triprotic acids every 0.5 pH units from pH 0.0 to 14.0. Plot the distribution diagram for each of the acids, and label the curve for each species. a. Citric acid b. Arsenic acid
> Calculate alpha values for the following diprotic acids every 0.5 pH units from pH 0.0 to 10.0. Plot the distribution diagram for each of the acids, and label the curve for each species. a. Phthalic acid b. Succinic acid c. Tartaric acid
> Calculate the p-value for each of the listed ions in the following: a. Na1, Cl2, and OH2 in a solution that is 0.0635 M in NaCl and 0.0403 M in NaOH. b. Ba2+, Mn2+, and Cl2 in a solution that is 4.65 ×10-3 M in BaCl2 and 2.54 M in MnCl2. c. H+, Cl-, and
> Derive equations that define a0, a1, a2, and a3 for the acid H3AsO4.
> For pH values of 2.00, 6.00, and 10.00, calculate the alpha values for each species in an aqueous solution of a. Phthalic acid. b. Tartaric acid. c. Citric acid. d. Periodic acid. e. Phosphorous acid. f. Malonic acid.
> Calculate a numerical value for the equilibrium constant for the reaction
> Formulate equilibrium constants for the following equilibria, and determine numerical values for the constants: a. b.
> A 0.6447-g portion of manganese dioxide was added to an acidic solution in which 1.1402 g of a chloride containing sample was dissolved. Evolution of chlorine took place as a consequence of the following reaction: After the reaction was complete, the ex
> Generate a curve for the titration of 50.00 mL of a solution in which the analytical concentration of HClO4 is 0.1000 M and that for formic acid is 0.0800 M. Calculate the pH after addition of 0.00, 10.00, 20.00, 24.00, 25.00, 26.00, 35.00, 44.00, 45.00,
> Generate a curve for the titration of 50.00 mL of a solution in which the analytical concentration of NaOH is 0.1000 M and that for hydrazine is 0.0800 M. Calculate the pH after addition of 0.00, 10.00, 20.00, 24.00, 25.00, 26.00, 35.00, 44.00, 45.00, 46
> Construct a curve for the titration of 50.00 mL of a 0.1000 M solution of compound A with a 0.2000 M solution of compound B in the following table. For each titration, calculate the pH after the addition of 0.00, 12.50, 20.00, 24.00, 25.00, 26.00, 37.50,
