ACS ANALYTICAL EXAM QUESTIONS
AND ANSWERS 2026
Solution A is analyzed for iron content using colorimetry. A calibration curve
(absorbance vs ppm) is prepared and the equation of the best-fit line is A = 0.0252 C
(ppm) - 0.0162. A 5.00-mL aliquout of Solution A is diluted to 100.0 mL and yields an
absorbance of 0.314. Calculate the concentration of iron in solution A.
0.65 ppm
2.62 ppm
13.1 ppm
262 ppm - ANSWERSA = 0.0252C-0.0162
A= absorbance
C= Concentration
Unknown absorbance = 0.314
Solve for C
0.314=0.0252xC-0.0162
C=13.1ppm
13.1 ppm is obtained by dilution 5.00mL solution A to 100.0 mL (20 times) so A must be
20 times value so 13.1x20= 262ppm
Given the data for the measurements of the concentration of iron in a blood sample:
9.4 µM•dL^-1,
10.6 µM•dL^-1,
9.2 µM•dL^-1,
10.0 µM•dL^-1,
9.6 µM•dL^-1
(average = 9.76 µM•dL-1, standard deviation = 0.56 µM•dL-1). Using the appropriate
test can any of the results be rejected at the 95% confidence level?
No, because Gcalc < Gtable or Qcalc < Qtable
No, because Gcalc > Gtable or Qcalc > Qtable
Yes, because Gcalc < Gtable or Qcalc < Qtable
Yes, because Gcalc > Gtable or Qcalc > Qtable - ANSWERSGrabbs test
Gcal = |questionable value-mean value|/st. dev = |10.6-9.76|/0.56 = 1.5
Gtable value for 5 at 95% is 1.672
, Gcal<Gtable = value restrained
Q test
Qcalc = gap/range = (10.6-10.0)/(10.6-9.2) = 0.428
Qcalc<Qtable = value restrained
No because Gcalc < Gtable or Qcalc < Qtable
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?
Yes, because tcalc < ttable
Yes, because tcalc > ttable
No, because tcalc < ttable
No, because tcalc > ttable - ANSWERShypothesis value = 1250
data value =1265
tcalc = (data value-hypothesis value)/st. dev*sqrt(no. of sets)
= (1265-1250)/(9*sqrt(5)) =3.73
Degree of freedom = n-1 so 5-1=4
ttable value for 4 at 95% is 2.776
Yes, tcalc>ttable
Which statement is correct about a determinate error in an analysis?
The determinate errors of a series of measurements of the same value have an equal
probability of being positive or negative.
The presence of a determinate error may cause the answer to vary regularly with
sample size.
The magnitude of a determinate error can be estimated from the precision of the
analysis.
A determinate error can always be detected and eliminated by performing a blank
analysis. - ANSWERSDifferent type of determinate errors:
1.Instrument errors
- failure to calibrate, degradation of parts in the
instrument, power fluctuations, variation in temperature, etc.
Can be corrected by calibration or proper instrumentation maintenance.
2. Method errors
AND ANSWERS 2026
Solution A is analyzed for iron content using colorimetry. A calibration curve
(absorbance vs ppm) is prepared and the equation of the best-fit line is A = 0.0252 C
(ppm) - 0.0162. A 5.00-mL aliquout of Solution A is diluted to 100.0 mL and yields an
absorbance of 0.314. Calculate the concentration of iron in solution A.
0.65 ppm
2.62 ppm
13.1 ppm
262 ppm - ANSWERSA = 0.0252C-0.0162
A= absorbance
C= Concentration
Unknown absorbance = 0.314
Solve for C
0.314=0.0252xC-0.0162
C=13.1ppm
13.1 ppm is obtained by dilution 5.00mL solution A to 100.0 mL (20 times) so A must be
20 times value so 13.1x20= 262ppm
Given the data for the measurements of the concentration of iron in a blood sample:
9.4 µM•dL^-1,
10.6 µM•dL^-1,
9.2 µM•dL^-1,
10.0 µM•dL^-1,
9.6 µM•dL^-1
(average = 9.76 µM•dL-1, standard deviation = 0.56 µM•dL-1). Using the appropriate
test can any of the results be rejected at the 95% confidence level?
No, because Gcalc < Gtable or Qcalc < Qtable
No, because Gcalc > Gtable or Qcalc > Qtable
Yes, because Gcalc < Gtable or Qcalc < Qtable
Yes, because Gcalc > Gtable or Qcalc > Qtable - ANSWERSGrabbs test
Gcal = |questionable value-mean value|/st. dev = |10.6-9.76|/0.56 = 1.5
Gtable value for 5 at 95% is 1.672
, Gcal<Gtable = value restrained
Q test
Qcalc = gap/range = (10.6-10.0)/(10.6-9.2) = 0.428
Qcalc<Qtable = value restrained
No because Gcalc < Gtable or Qcalc < Qtable
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?
Yes, because tcalc < ttable
Yes, because tcalc > ttable
No, because tcalc < ttable
No, because tcalc > ttable - ANSWERShypothesis value = 1250
data value =1265
tcalc = (data value-hypothesis value)/st. dev*sqrt(no. of sets)
= (1265-1250)/(9*sqrt(5)) =3.73
Degree of freedom = n-1 so 5-1=4
ttable value for 4 at 95% is 2.776
Yes, tcalc>ttable
Which statement is correct about a determinate error in an analysis?
The determinate errors of a series of measurements of the same value have an equal
probability of being positive or negative.
The presence of a determinate error may cause the answer to vary regularly with
sample size.
The magnitude of a determinate error can be estimated from the precision of the
analysis.
A determinate error can always be detected and eliminated by performing a blank
analysis. - ANSWERSDifferent type of determinate errors:
1.Instrument errors
- failure to calibrate, degradation of parts in the
instrument, power fluctuations, variation in temperature, etc.
Can be corrected by calibration or proper instrumentation maintenance.
2. Method errors
