Analytical Chemistry Final Exam QUESTIONS & ANSWERS(RATED A+)

Analytical Chemistry Final Exam
QUESTIONS & ANSWERS(RATED A+)
which of the following is not true regarding "weak electrolytes"?
a) have primarily molecular bonding in solution
b) dissociate only partially in water to form ions
c) dissociate more completely as their concentration increases
d) acetic acid is an example of a "weak electrolyte" - ANSWER c) dissociate more
completely as their concentration increases

which of the following terms in incorrectly defined?
a) titration error: the difference between the end point and the equivalence point
b) direct titration: titrant is added to analyte until the rection is complete
c) equivalence point: volume of titrant added in excess of the end point to change a
physical property of the analyte solution
d) blank titration: titration performed without analyte to calculate titration error
standardization: titration of a known amount of analyte to determine the concentration of
the titrant - ANSWER c) equivalence point: volume of titrant added in excess of the end
point to change a physical property of the analyte solution

which of the following are true regarding internal standards?
i) the response factor is calculated by using a mixture containing known amounts of
analyte and internal standard and by using detector response to the analyte and the
internal standard
ii) internal standards are useful where instrument response or quantity of sample
analyzed varies over time
iii) detector response is inversely proportional to concentration
iv) detector response to analyte and internal standard is assumed to be constant over a
range of concentrations - ANSWER i, ii, iv

for precipitation titration of anlyte X- by titrant M+, which of the following statements is
not true?
a) concentration M+ at the equivalence point is the molar solubility of MX or [M+] = sqr
root (ksp)
b) concentration M+ past the equivalence point is the excess [M+] after reacting with all
of the X-
c) concentration of M+ before the equivalence point is [M+] = Ksp/[X-1]
d) the plot of the titration curve is [M+] vs VM+
e) the titration reaction of M+ (aq) + X- (aq) -> MX (s) - ANSWER d) the plot of the
titration curve is [M+] vs VM+

for the graphical equivalence point determination (titration curve) for a precipitation
reaction, which of the following is (are) correct?
i. the steepest slope of the titration curve is at the equivalence point

,ii. the equivalence point occurs where the first derivative of the titration curve maximizes
iii. the equivalence point occurs where the second derivative of the titration curve equals
zero - ANSWER i, ii, and iii

all of the following are true for activities and activity coefficients, except:
a) activity for a chemical species is the product of concentration and activity coefficient
b) the activity coefficient corrects for non-ideal behavior due to ionic strength
c) as ionic strength increases, the value of the activity coefficient increases
d) for ions, the activity coefficient approaches unity as the ionic strength decreases
e) the activity coefficient for neutral molecules is approximately unity - ANSWER c) as
ionic strength increases, the value of the activity coefficient increases

for a fixed absolute uncertainty, as the magnitude of the measure _____, the percent of
relative uncertainty _____
(fill each blank with either increases or decreases) - ANSWER increases; decreases
(vice versa)

which of the following statement about the confidence interval (CI) is false?
a) req. use of the student's t
b) the CI at 50% confidence level is broader than that at 90%
c) The CI relates the true mean to the measured mean
d) the CI narrows as t decreases - ANSWER b) the CI at 50% confidence level is
broader than that at 90%

which of the following statements is true?
a) Keq for an exothermic reaction decreases with increasing temperature
b) positive values for delta H and delta S favor a reaction
c) the more positive delta G, the greater Keq
d) comparative solubilites can be determined by comparing Ksp values - ANSWER a)
Keq for an exothermic reaction decreases with increasing temperature

which of the following is not true for weak acids and weak bases?
a) Kw=Ka x Kb
b) Kb = [B][OH-]/[BH+]
c) Ka = [H+][A-]/[HA]
d) pKa = -logKa
e) pKb = - log Kb - ANSWER b) Kb = [B][OH-]/[BH+]

for the silver half-reaction, Ag+ + 1e- -> Ag (s), when the concentration of the silver
cation is increased, the reduction potential
a) becomes more positive
b) becomes more negative
c) remains constant
d) increases or decreases depending on the voltage of the other half-reaction
e) increases or decreases depending on the temperature - ANSWER a) becomes more
positive

, which of the following statements is not true?
a) an oxidizing agent gains electrons in a redox reaction
b) a current of one ampere represents one coulomb per second
c) for M+ + e- -> M(s) and E standard of -2.5v means M(s) is a good oxidizing agent
d) the electrode at which reduction occurs is defined as the cathode - ANSWER c) for
M+ + e- -> M(s) and E standard of -2.5v means M(s) is a good oxidizing agent

which of the following is not true for galvanic cells?
a) galvanic cells are spontaneous
b) oxidation occurs at the anode and reduction occurs at the cathode
c) electrons move toward more negative electrical potential
d) galvanic cells are composed of two half-cells connected by a salt bridge
e) the salt bridge maintains electroneutrality throughout the cells - ANSWER c)
electrons move toward more negative electrical potential

which of the following statements is not true?
a) electrons flow from the negative terminal of a battery
b) a reducing agent gives up electrons in a redox reaction
c) a standard reduction potential can be deduced from its poitential vs a SHE
d) a spontaneous cell requires one half cell to have a negative E standard - ANSWER
d) a spontaneous cell requires one half cell to have a negative E standard

the ________ gives the relative response of an ion-selective electrode to different
species with the same charge
a) counter ion coefficient
b) isoionic coefficient
c) ion coefficient
d) selectivity coefficient
e) transient coefficient - ANSWER d) selectivity coefficient

in the redox titration of Fe2+ with Ce4+, which statement is not true? Fe3+ + e- -> Fe+2
E standard = +0.732V Ce4+ + e- > Ce+3+ E standard = 1.70 V
a) the resulting titration curve is symmetrical about the equivalence point potential
b) the analyte and titrant react in a 1:1 stoichiometry
c) after the equivalent point, potential is based on concentration of Fe+3 and Fe2+
d) At equivalence point, the concentrations of Ce+4, Ce+3. Fe+2, and Fe+3 cancel out -
ANSWER c) after the equivalent point, potential is based on concentration of Fe+3 and
Fe2+

all of the following statements are true except
a) an ion selective electrode responds to the concentration of the free analyte ion in
solution
b) the fluoride ion electrode uses an inorganic salt crystal as the ion-selective
membrane
c) ion selective electrodes can be used in colored or cloudy solutions