Questions and Answers of Quantitative Chemical Analysis 9th edition

A titration curve for Na2CO3 titrated with HCl is shown here. Suppose that both phenolphthalein and Bromo cresol green are present in the titration solution. State what colors you expect to observe
The graph shows the titration curve for a protein containing 124 amino acids with 16 basic and 20 acidic substituents. The curve is smooth without clear breaks because 29 groups are titrated in the
A 50.0-mL solution of 0.031 9 M benzylamine was titrated with 0.0500 M HCl. Calculate the pH at the following volumes of added acid: Va 5 0, 12.0, 12 Ve, 30.0, Ve, and 35.0 mL.
Calculate the mean HCl molarity, standard deviation, and relative standard deviation.
Calculate the average molarity (x-), the standard deviation (s), and the relative standard deviation (s/√x). If you have used some care, the relative standard deviation should be < 0.2%.
Titrate one blank prepared from 3 drops of indicator plus 50 mL of 0.05 M NaCl. Subtract the blank volume of HCl from that required to titrate Na2CO3.
Calculate the volume of NaOH required for each of the other three samples and titrate them carefully. During each titration, periodically tilt and rotate the flask to wash liquid from the walls into
Why is it not practical to titrate an acid or base that is too weak or too dilute?
Carefully titrate each of the other samples until it just turns from blue to green. Then boil the solution to expel CO2. The solution should return to a blue color. Carefully add HCl from the buret
Consider the titration of 50.0 mL of 0.050 0 M malonic acid with 0.100 M NaOH. Calculate the pH at each point listed and sketch the titration curve: Vb = 0.0, 8.0, 12.5, 19.3, 25.0, 37.5, 50.0, and
Boil 1 L of water for 5 min to expel CO2. Pour the water into a polyethylene bottle, which should be tightly capped whenever possible. Calculate the volume of 50 wt% NaOH needed (∼5.3 mL) to
Buoyancy correction factor: mtrue/mread = 1.000 3244][Interpolated density of water at 23.3 °C: 0.997 468 9 g/mL][HCl concentration at 20 °C: 0.102343 M]Reagents: The
Dry primary-standard-grade potassium hydrogen phthalate for 1 h at 110oC and store it in a desiccator. CO,K+ CO, K+ + NaOH + H,0 CO,H CO, Na+ Potassium hydrogen phthalate FM 204.221
The inside cover of this book tells us that 8.2 mL of ∼37 wt% HCl should be added to 1 L of water to produce ∼0.1 M HCl. Prepare this solution in a capped polyethylene bottle, using a graduated
Prepare 50 wt% aqueous NaOH solution in advance and allow the Na2CO3 precipitate to settle overnight. (Na2CO3 is insoluble in this solution.) Store the solution in a tightly sealed polyethylene
Explain what is wrong with the following statement: At its isoelectric point, the charge on all molecules of a particular protein is 0.
A solution was prepared from 10.0 mL of 0.100 M cacodylic acid and 10.0 mL of 0.080 0 M NaOH. To this mixture was added 1.00 mL of 1.27 × 1026 M morphine. Calling morphine B, calculate the fraction
Calculate αH2A, αHA-, and αA2- for cis-butenedioic acid at pH 1.00, 1.92, 6.00, 6.27, and 10.00.
Find the pH and the concentration of each species of lysine in a solution of 0.010 0 M lysine ? HCl, lysine monohydrochloride. The notation “lysine ? HCl” refers to a neutral lysine molecule that
Phosphate at 0.01 M is one of the main buffers in blood plasma, whose pH is 7.45. Would phosphate be as useful if the plasma pH were 8.5?
Calculate the pH of a 0.010 M solution of each amino acid in the form drawn here. H,N* NH2 NH2 NH C=0 CH2 CH2 S CH2 CH2 CH2 CH2 (a) H¿ÑCHCO, (b) H3ÑCHCO, (c) H,NCHCO, Glutamine Cysteine Arginine
Interpreting spectral data. The graph shows the 1H-nuclear magnetic resonance chemical shift of the H4 proton on pyridine as a function of pH. Chemical shift is related to the environment of a proton
Consider a reaction mixture containing 100.0 mL of 0.100 M borate buffer at pH = pKa = 9.24. At pH = pKa, we know that [H3BO3] = [H2BO-3 ] = 0.050 0 M. Suppose that a chemical reaction whose pH we
Describe how to prepare 250 mL of 1.00 M ammonia buffer, pH 9.00, starting with 28 wt% NH3 (“concentrated ammonium hydroxide” listed on the back inside cover of the book) and “concentrated”
The pH of 0.010 M o-cresol is 6.16. Find pKa for this weak acid. CH3 0-Cresol ОН
Neglecting activity coefficients, calculate the pH of 5.0 × 10-8 M HClO4. What fraction of H+ is derived from dissociation of water?
Neglecting activity coefficients, calculate the pH of (a) 1.0 × 10-3 M HBr; (b) 1.0 × 10-2 M KOH.
Find the concentrations of the major species in a saturated aqueous solution of LiF. Consider these reactions:(a) Look up the equilibrium constants in the appendixes and write their pK values. The
Modify Figure 8-7 to find the concentrations of species in 0.05 M NH3. The only change required is the value of F. How do the pH and fraction of ammonia hydrolysis (= [NH+4 ]/([NH+4 ] + [NH3]))
A 40.0-mL solution of 0.040 0 M Hg2(NO3)2 was titrated with 60.0 mL of 0.100 M KI to precipitate Hg2I2 (Ksp = 4.6 × 10-29). (a) Show that 32.0 mL of KI are needed to reach the equivalence
Color Plate 4 shows how the color of the acid-base indicator bromocresol green (H2BG) changes as NaCl is added to an aqueous solution of (H+)(HBG-). Explain why the color changes from pale green to
Use Equation 7-12 to reproduce the curves in Figure 7-3. Plot your results on a single graph. F(Kp = 8.3 x 10-17) %3D 14 12 Br (Kp = 5.0 x 10-13) %D 10 CF (K = 1.8 x 10-10) sp -Br 2 10 20 30 40 50 60
A mixture having a volume of 10.00 mL and containing 0.1000 M Ag+ and 0.100 0 M Hg22+ was titrated with 0.1000 M KCN to precipitate Hg2(CN)2 and AgCN. (a) Calculate pCN- at each of the following
A barium sulfate precipitation titration described at the opening of this chapter is shown in the figure. The initial concentration of Cl- before adding BaCl2 was 0.000 19 M in 25 mL of aqueous
Managing a salt-water aquarium. A tank at the New Jersey State Aquarium has a volume of 2.9 million liters. Bacteria are used to remove nitrate that would otherwise build up to toxic levels. Aquarium
A solid mixture weighing 0.05485 g contained only ferrous ammonium sulfate and ferrous chloride. The sample was dissolved in 1 M H2SO4, and the Fe2+ required 13.39 mL of 0.01234 M Ce4+ for complete
Consider the titration of 50.00 (0.05) mL of a mixture of I and SCN with 0.068 3 (0.000 1) M Ag. The first equivalence point is observed at 12.6 (0.4) mL, and the second occurs at 27.7 (0.3)
What is the difference between a reagent-grade chemical and a primary standard?
Construct a graph of pAg+ versus milliliters of Ag+ for the titration of 40.00 mL of solution containing 0.050 00 M Br- and 0.050 00 M Cl-. The titrant is 0.084 54 M AgNO3. Calculate pAg+ at the
A 50.0-mL sample of 0.080 0 M KSCN is titrated with 0.040 0 M Cu+. The solubility product of CuSCN is 4.8 × 10-15. At each of the following volumes of titrant, calculate pCu+, and construct a graph
A solid sample weighing 0.237 6 g contained only malonic acid and aniline hydrochloride. It required 34.02 mL of 0.087 71 M NaOH to neutralize the sample. Find the weight percent of each component in
A solution of NaOH was standardized by gravimetric titration of a known quantity of the primary standard, potassium hydrogen phthalate:Potassium hydrogen phthalate C8H5O4K, FM 204.22The NaOH was then
Ascorbic acid (vitamin C) reacts with I-3 according to the equationStarch is used as an indicator in the reaction. The end point is marked by the appearance of a deep blue starch-iodine complex
Explain why hydrated metal ions such as (H2O)6Fe3+ hydrolyze to give H+, but hydrated anions such as (H2O)6Cl= do not hydrolyze to give H+.
Make a list of the common strong acids and strong bases. Memorize this list.
Calculate [H+] and pH for the following solutions:(a) 0.010 M HNO3 (b) 0.035 M KOH (c) 0.030 M HCl(d) 3.0 M HCl(e) 0.010 M [(CH3)4N+]OH-
Distinguish Lewis acids and bases from Brønsted-Lowry acids and bases. Give an example of each.
Although KOH, RbOH, and CsOH have little association between metal and hydroxide in aqueous solution, Li+ and Na+ do form complexes with OH-:Prepare a table like the one in Exercise 6-B showing
For the reaction HCO-3 ⇋ H+ + CO2-3 , Δ G° = 159.0 kJ/mol at 298.15 K. Find the value of K for the reaction.
Is it possible to precipitate 99.0% of 0.010 M Ce3+ by adding oxalate (C2O24-) without precipitating 0.010 M Ca2+?CaC2O4 Ksp = 1.3 × 10-8Ce2(C2O4)3 Ksp = 5.9 × 10-30
Figure 5-10 is a graph of AX/AS versus [X]/[S] 5 (mol% vinyl acetate units)/(mol% ethylene units) 5 q/p in Reaction 5- 13.In figure 5-10(a) Construct the graph in Figure 5-10 from the following data:
Figure 3-3 requires gridlines to read buret corrections. In this exercise, you will format a graph so that it looks like Figure 3-3. Follow the procedure in Section 2-11 to graph the data in the
A solution containing 3.47 mM X (analyte) and 1.72 mM S (standard) gave peak areas of 3 473 and 10 222, respectively, in a chromatographic analysis. Then 1.00 mL of 8.47 mM S was added to 5.00 mL of
Lead in dry river sediment was extracted with 25 wt% HNO3 at 358C for 1 h. Then 1.00 mL of filtered extract was mixed with other reagents to bring the total volume to V0 5 4.60 mL. Pb(II) was
Standard addition graph. Allicin is a ~0.4 wt% component in garlic with antimicrobial and possibly anticancer and antioxidant activity. It is unstable and therefore difficult to measure. An assay was
Europium is a lanthanide element found at parts per billion levels in natural waters. It can be measured from the intensity of orange light emitted when a solution is illuminated with ultraviolet
Standard addition graph. Tooth enamel consists mainly of the mineral calcium hydroxyapatite, Ca10(PO4)6(OH)2. Trace elements in teeth of archeological specimens provide anthropologists with clues
Synthetic data are given below for a calibration curve in which random Gaussian noise with a standard deviation of 80 was superimposed on y values for the equation y = 26.4 x 1 1.37. This exercise
What is the difference between repeatability and reproducibility? Define the following terms: instrument precision, intra-assay precision, intermediate precision, and interlaboratory precision. Which
Internal standard graph. Data are shown below for chromatographic analysis of naphthalene (C10H8), using deuterated naphthalene (C10D8, in which D is the isotope 2H) as an internal standard. The two
In Figure 5-6, the x-intercept is 22.89 mM and its standard uncertainty is 0.098 mM. Find the 90% and 99% confi dence intervals for the intercept. y = 0.646 3x + 1.868 7 В Readings obtained with
Explain the meaning of the quotation at the beginning of this chapter: “Get the right data. Get the data right. Keep the data right.”
(a) The linear calibration curve in Figure 4-13 is y 5 0.016 30 (±0.000 22) x 1 0.0047 (±0.0026) with sy = 0.0059. Find the quantity of unknown protein that gives a measured absorbance of 0.264
A calibration curve based on n = 10 known points was used to measure the protein in an unknown. The results were protein = 15.22 (±0.46) μg, where the standard uncertainty is ux = 0.46 μg. Find
Which statement about the F test is true? Explain your answer.(i) If Fcalculated < Ftable, there is more than a 5% chance that the two sets of data are drawn from populations with the same
Bicarbonate in replicate samples of horse blood was measured four times by each of two methods with the following results: Method 1: 31.40, 31.24, 31.18, 31.43 mMMethod 2: 30.70, 29.49, 30.01,
Students at Francis Marion University measured the mass of each M&M candy in 16 sets of 4 candies and in 16 sets of 16 candies(a) Find the mean of the 16 values on the left side of the table and
Let’s create a spreadsheet to compute the mean and standard deviation of a column of numbers in two different ways. The spreadsheet here is a template for this exercise.(a) Reproduce the template
For the numbers 116.0, 97.9, 114.2, 106.8, and 108.3, find the mean, standard deviation, standard uncertainty (= standard deviation of the mean), range, and 90% confidence interval for the mean.
(a) Show that the formula mass of NaCl is 58.442 ± 0.006 g/mol. (b) To prepare a solution of NaCl, you weigh out 2.634 (±0.002) g and dissolve it in a volumetric flask whose volume is 100.00
The pH of a solution is 4.44 ± 0.04. Find [H1] and its absolute uncertainty.
(a) How many milliliters of 53.4 (±0.4) wt% NaOH with a density of 1.52 (±0.01) g/mL will you need to prepare 2.000 L of 0.169 M NaOH? (b) If the uncertainty in delivering NaOH is ±0.01 mL,
An empty crucible weighs 12.437 2g and the same crucible containing a precipitate from a gravimetric analysis weighs 12.529 6g.(a) Each mass has six significant digits. What is the mass of
Accuracy of serial dilution. To make a 1/100 dilution of a solution, which, if either, procedure provides more accuracy: (i) Transfer 1 mL with a pipet to a 100-mL volumetric flask or (ii)
Accounting for buoyancy, what apparent mass of CsCl (density = 3.988 g/mL) in air should you weigh out to obtain a true mass of 1.267 g?
(a) How much of the primary standard benzoic acid (FM 122.12, density = 1.27 g/mL) should you weigh out to obtain a 100.0 mM aqueous solution in a volume of 250 mL? (b) What apparent mass in air
(a) Figure 1-1 shows a peak O3 concentration of 19 mPa in the stratosphere. Figure 1-3 shows a peak concentration of O3 of 39 ppb at ground level at one particular location. To compare these
Quartz crystal microbalance. The area of the gold electrodes on the quartz crystal microbalance at the opening of Chapter 2 is 3.3 mm2. One gold electrode is covered with DNA at a surface density of
Explain the principle of operation of an electronic balance.
What does “green chemistry” mean?
A stock solution contains 51.38 mmol KMnO4/L. How can you use pipets in Table 2-4 plus a 100- or 250-mL volumetric flask to obtain approximately 1, 2, 3, and 4 mmol KMnO4/L? What will be the exact
What class of liquids might easily penetrate through rubber gloves and get onto your skin? Would rubber gloves protect you from concentrated hydrochloric acid?
(a) What is the primary safety rule and what is your implied responsibility to make it work?(b) After safety features and safety procedures in your laboratory have been explained to you, make a list
How many grams of 50 wt% NaOH (FM 40.00) should be diluted to 1.00 L to make 0.10 M NaOH?
Defi ne the following terms:(a) Molarity(b) Molality(c) Density(d) Weight percent(e) Volume percent(f) Parts per million(g) Parts per billion(h) Formal concentration
I have always enjoyed eating tuna fish. Unfortunately, a study of the mercury content of canned tuna in 2010 found that chunk white tuna contains 0.6 ppm Hg and chunk light tuna contains 0.14 ppm.
What is the absolute uncertainty in mass (±? Da) at m/z 100 and at m/z 20 000 if the mass accuracy of a spectrometer is 2 ppm?
An ion with the formula C7H10NO2+ appears at m/z 140. (a) Write the formulas of the isotopologues contributing to m/z 141 and predict the intensity at m/z 141 relative to the intensity at m/z
What resolving power is required to distinguish CH3CH+2 from HC=O+?
Measure the width at half-height of the peak at m/z 53 and calculate the resolving power of the spectrometer from the expression m/m1/2. Would you expect to be able to resolve two peaks at 100 and
How much energy in kJ/mol is released when nitrogen emits Ka radiation at 0.392 keV? Compare the Ka energy to 945 kJ/mol, which is the energy required to break the triple bond in N2 (one of the
Why are La and Lb peaks, but not Ka and Kb peaks for lead identified in Figure 21-31? Why are La and Lb peaks not identified for iron in Figure 21-31?In Figure 21-31 350 Fe K. 300 250 Pb L. Sr K. Se
Where would Kb emission peaks for Ti, Se, and Zr be found in Figure 21-31? Why are they not labeled?In Figure 21-31 350 Fe K. 300 250 Pb L. Sr K. Se K. Pb La 200 150 Cd K. Ag K Bremsstrahlung (broad
Explain why X-ray fluorescence is observed when matter absorbs X-rays of sufficient energy. Why does each element have a unique X-ray signature?
Why is an internal standard most appropriate for quantitative analysis when unavoidable sample losses are expected during sample preparation?
Bone consists of the protein collagen and the mineral hydroxyapatite, Ca10(PO4)6(OH)2. The Pb content of archaeological human skeletons measured by graphite furnace atomic absorption sheds light on
In Figure 20-35, the relative detection limit is 37 after 1 s of signal averaging, 12.5 after 10 s, and 5.6 after 40 s of signal averaging. Based on the value of 37 at 1 s, what are the expected
The interferometer mirror of a Fourier transform infrared spectrophotometer travels 61 cm.(a) How many centimeters is the maximum retardation, D?(b) State what is meant by resolution.(c) What is the
An 18-W compact fluorescent bulb produces approximately the same amount of light as a 75-W incandescent bulb that screws into the same socket. The fluorescent bulb lasts ~10 000 h and the
Vapor at a pressure of 30.3 mbar from the solid compound pyrazine had a transmittance of 24.4% at a wavelength of 266 nm in a 3.00-cm cell at 298 K.(a) Convert transmittance to absorbance.(b) Convert

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