Analytical Chemistry
Calculate the concentration of silver ions that would result if a saturated solution of silver sulfate, AgSO4 (Ksp = 1.5e-5) was made. (ignore sulfate ion hydrolysis) a) 2.74e-3M b) 3.87e-3M c) 1.55e-2M d) 3.11e-2M
d
Calculate the moles of oxalic acid dihydrate, H2C2O4*2H2O (fw=126.07), needed to react with 10mL of 0.02731M ceric sulfate, Ce(SO4)2, given the reaction H2C2O4 + 2Ce^4+ --> 2CO2 + 2Ce^3+ + 2H+ a) 0.1366 moles b) 5.462e-4 moles c) 2.731e-4 moles d) 1.366e-4 moles
d
In acidic solution, dichromate is reduced to the chromic ion by this half-reaction Cr2O7^2- + 14H+ +ne- --> 2Cr^3+ + 7H20 what is the value of n for this process? a) 2 b) 3 c) 4 d) 6
d
A 0.01M solution of AgNO3 has a concentration of Ag+ ion equivalent to (molar mass of Ag+ = 108g/mol and AgNO3 = 170g/mol) a) 1080 ppb b) 1080 ppm c) 1700 ppm d) 10.0 ppm
b
A standard solution is prepared by dissolving 10.6192g of (NH4)2Ce(NO3)6 (molar mass = 548.23g/mol, 98.75% purity) in dilute sulfuric acid. The resulting solution is quantitatively transferred to a 500mL volumetric flask and diluted to the mark. what is the [Ce] in the final solution? a) 0.03826M b) 0.03874 M c) 0.03923 M d)0.07651M
a
Caffeine in a sample of chocolate was measured five times, and the results were 1265 ppm caffeine with a standard deviation of 9 ppm. According to the product label, the chocolate contains 1250 ppm caffeine. Are the experimental results statistically different from the label value at the 95% confidence level? a) yes because tcal>tcrit b) yes because tcal<tcrit c) no because tcal>tcrit d) no because tcal<tcrit
a
Potentiometric methods involve the measurement of a) a potential difference between the indicator and reference electrodes under non-equilibrium conditions b)a potential difference between the indicator and reference electrodes under equilibrium conditions c) the current at the indicator electrode under non-equilibrium conditions d) the current at the indicator electrode under equilibrium conditions
a
Which is not a characteristic of a primary standard? a) it is hygroscopic b) it is thermally stable c) it has accurately known purity d) its reactions are known and stiochiometric
a
Which is not a characteristic of gas chromatography? a) often used for large molecules b) is often connected to a mass spectometer c) temperature must be tightly controlled d) columns are often 20-30 meters long
a
Calculate the pH of a solution prepared by dissolving 2.129g of solid anhydrous Na2HPO4 (fw = 141.98) in about 50mL of water, adding 1.0mL of 6.0M HNO3, and diluting the mixture with water to 100mL. The stepwise acid dissociation constants for phosphoric acid are 7.11e-3, 6.32e-8, and 7.1e-13. Assume the activity coefficients are equal to 1.00 a) 7.02 b) 7.38 c) 9.85 d) 12.32
b
Calculate the voltage of the cell Ag(s)/AgBr(s),NaBr(aq, 1.0M)//CdCl2(aq, 0.05M)/Cd(s) AgBr + e --> Ag + Br Ecell = 0.071V Ag + e --> Ag Ecell = 0.799V Cd + 2e --> Cd Ecell = -0.402V Ksp(AgBr) = 5e-13 a) -0.678V b) -0.511V c) -0.423V d) 0.511V
b
Given the data for the measuremtns of the concetration of iron in a blood sample: 9.4microM/dL, 10.6microM/dL, 9.2microM/dL, 10.0microM/dL, 9.6microM/dL (average = 9.76microM/dL, STD = 0.56microM/dL). Using the appropriate test can any of the results be rejected at the 95% confidence level. a) no because, Qcal<Qcrit or Gcal<Gcrit b) no because, Qcal>Qcrit or Gcal>Gcrit c) yes because, Qcal<Qcrit or Gcal<Gcrit d) yes because, Qcal>Qcrit or Gcal>Gcrit
b
If a weak monoprotic acid, HA, is titrated with strong base, what is NOT true at the half equivalence point? a) pH = pKa b) pH = 7.0 c) [HA] = [A] d) buffer capacity is maximized
b
In a matrix of unknown or ambiguous content, a good approach to determination of an analyte is to use a) a linear calibration curve method b) a standard addition method c) a method of least squares d) an external standard method
b
In its protonated form, bromothymol blue has a molar absorptivity of 13800 /M*cm at 435nm. At the same wavelength, the deprotonated form of bromothymol blue has molar absorptivity of 3410 /M*cm. If a solutin contains 2.8e-5M protonated bromothymol blue and 5e-5M deprotonated bromothymol blue, what is the absorbance of the solution in a 1.00cm sample cell at 435nm? a) 0.228 b) 0.557 c) 0.785 d) 1.34
b
In the spectrophotometric analysis of benzene, the calibration curve has a slope of 195AU/M and an intercept of 0.079AU. If an unknown has an absorbance of 0.517 AU, what is the concentration of benzene in the sample? a) 2.09e-4M b) 2.25e-3M c) 2.65e-3M d) 0.438M
b
The data was obtained for the liquid chromatographic separation of two organic molecules, A and B, on a 0.25cm reversed phase column with a flow rate of 1.0mL/min. An unretained molecule elutes from the column at 1.1 min A = 2.7 retention time = 0.21 peak width B = 6.3 retention time = 0.48 peak width calculate the capacity factor, k', for compound B a) 1.5 b) 4.7 c) 5.7 d) 13.1
b
A buffer was prepared by mixing 1.00mol of formic acid and 1.00mol of sodium formate in 1.00L of distilled water. A 100mL aliquot of 1.00M HCl is then added. What is the pH of the resulting buffer solution? (pKa of formic acid = 3.74) a) 3.83 b) 3.74 c) 3.65 d) 3.33
c
How many milliliters of concentrate sulfuric acid, which is 96% (w/w) pure H2SO4, are needed to prepare 500mL of a 2.0M solution of sulfuric acid? (molar mass = 98.08g/mol, density = 1.831g/mL) a) 28 mL b) 51 mL c) 56 mL d) 96 mL
c
The order of compontents in a typical flame atomic absorption spectrometer is a) flame-hollow cathode lamp-monochromator-detector b) flame-monochromator-hollow cathode lamp-detector c) hollow cathode lamp-flame-monochromator-detector d) hollow cathode lamp-monochromator-flame-detector
c
What is the relative retention for compounds A and B if the retention time for A (ta) is 3.91 min, the retention time for (tb) is 6.42 min, and the tm is 1.34 min? a) 0.51 b) 1.64 c) 1.98 d) 3.79
c
Which ion is the strongest reducing agent under standard conditions? You should refer to the E data table E(Ti^3+, Ti^2+) = -0.90V E(Zn^2+, Zn) = -0.80V E(Cr^3+, Cr) = -0.744V E(Cu^2+, CU) = -0.42V E(Fe^3+, Fe^2+) = 0.771V E(Hg^2+, Hg2^2+) = 0.908V a)Cr^2+ b)Hg2^2+ c)Ti^2+ d)Fe^2+
c
A 3.31e-4M solution of a new drug (273g/mol) has an absorbance of 0.750 in a 1cm cell. A 0.3122g tablet containing the drug is dissolved in water to a final volume of 500mL, and has an absorbance of 0.654 under the same conditions. What is the mass percent of the drug in the tablet? a) 87.4 b) 56.9 c) 18.9 d) 12.6
d
A student determined the concentration of a sodium hydroxide solution, and after four runs she reported a value of 0.1053M with 98% confidence limits of +/- 0.0014M. Assuming that no systematic errors were involved, which statement is true? a) the true value must be between 0.1039M and 0.1067M b) there is a 2% probability that the true value is greater than 0.1067M c) if the student repeats the analysis 100 more times, 98 of the values will be between 0.1039M and 0.1067M d) there is a 98% probability that the true value lies between 0.1039M and 0.1067M
d
Solution A is analyzed for iron content using colorimetry. A calibration curve is prepared and the equation of the best-fit line is A=0.0252 C - 0.0162. A 5mL aliquout of Solution A is diluted to 100mL and yields an absorbance of 0.314. Calculate the concentration of iron is solution A. a)0.65 b)2.62 c)13.1 d)262
d
What is the pH at the equivalence point for a titration of 20.00mL of 0.0250M NaOH? Assume the activity coefficients are equal to 1.00. a) 5.95 b) 7.00 c) 3.74 d) 7.92
d
Which compound will elute first in a reversed phase HPLC separation? a) CH3(CH2)8CH3 b) CH3(CH2)9OH c) CH3(CH2)4CH3 d) CH3(CH2)5OH
d
Which is the most complete charge balance expression for a saturated solution of CaC2O4? a) [Ca^2+] = [C2O4^2-] b) 2[Ca^2+] = 2[C2O4^2-] + [HC2O4-] c) [H+] + 2[Ca^2+] = [OH-] + 2[C2O4^2-] d) [H+] + 2[Ca^2+] = [OH-] + 2[C2O4^2-] + [HC2O4-]
d
Which statement is correct about a determinate error in an analysis? a) the determinate errors of a series of measurements of the same value have an equal probability of being positive or negative b) the presence of a determinate error may cause the answer to vary regularly with sample size c) the magnitude of a determinate error can be estimated form the precision of the analysis d) a determinate error can always be detected and eliminated by preforming a blank analysis
d
Which will not result in a deviation from Beer's law? a) molecular interactions between analyte molecules b) polychromatic radiation form the source c) stray light reaching the detector d) a dilute sample solution
d
