Faculty of Science
Department of Chemistry
Analytical Chemistry 11012131
Semester: Second 2021/2022
HW 1
1. Which of the following are examples of systematic errors?
I.
Weighing a precipitate on an electronic balance.
II.
Consistently reading burette volumes from the top of the meniscus.
III.
Using an incorrectly labelled standard solution in a titration.
a) II and III only
b) I and III only
c) I and II only
d) I, II and III
2. Which of the following is the best definition of precision?
a) How close a value is to the true value.
b) A measure of how good an experimenter's technique is.
c) A measure of the reproducibility of a result.
d) The accuracy of a measurement.
3. Which of the following statements is false?
a) All precise results are accurate.
b) Accurate results agree closely with the accepted value.
c) Highly accurate results are usually precise.
d) Precise results have a smaller range than imprecise results.
4. Which of the following statements about systematic errors is false?
a) Systematic errors may be associated with technique or equipment.
b) Repeating an experiment many times and averaging the result minimizes systematic error
and increases accuracy.
c) Systematic errors always bias the result in the same direction.
d) Poorly calibrated instruments may be a cause of systematic errors.
5. What is the uncertainty in a measurement taken on an electronic balance that reads mass (in
grams) to two decimal places?
a) ±0.005 g
b) ±0.01 g
c) ±0.001 g
d) ±0.05 g
6. If the measured value is the average of several measurements, the error is called the....
a) Mean Error
b) Systematic Error
c) Random Error
d) Absolute Error
7. Not transferring all solid/liquid when preparing samples into a volumetric flask
a) Random error
b) Systemic error
8. Accuracy is the closeness of the experimental value to the true value. So, arrange the correct
accuracy present following the diagram given.
a)
b)
c)
d)
High accuracy, high accuracy, low accuracy, low accuracy
Low accuracy, high accuracy, high accuracy, low accuracy
High accuracy, low accuracy, high accuracy, low accuracy
Low accuracy, low accuracy, high accuracy, high accuracy
9. Which statement true about instrument errors?
a) Errors of these types usually are detectable and correctable
b) Difficult to detect and hence, these errors are usually the most difficult to identify and
correct
c) Many measurements require personal judgments.
d) The presence of interfering contaminants in the sample
10. A method of analysis yields weights for gold that are low by 0.4 mg. what type of error is
introduced into your analysis if you use this method:
a) Indeterminate error
b) Constant determinate error
c) Proportioned determinate error
d) Personal error
e) Gross error
11. You are testing a new method for analysis of Cu2+ in sample. A sample known to contain
13.3 ppm Cu2+ is analyzed by the new procedure and the following concentrations of Cu 2+ in
ppm are found: 14.7, 14.3, 14.6, 14.4, and 14.3. These experiments demonstrate:
a)
b)
c)
d)
e)
The presence of gross mistakes
The absence of determinate errors in the procedure
The presence of indeterminate errors
The presence of personal errors
The presence of a determinate method error in the new procedure
12. Rinsing pipette with distilled water
a) Random error
b) Systemic error
13. Using wrong amount of indicator for one of the titration
a) Random error
b) Systemic error
14. Which of the following error is caused by poor calibration of the instrument?
a) Random error
b) Gross error
c) Systematic error
d) Precision error
15. Two students determined the concentration of a hydrogen peroxide solution by the same
volumetric technique. They each carried out the analysis in triplicate and obtained the results
you see in the data table. The true concentration of the hydrogen peroxide solution is 0.893
mol L-1. Did student A or student B achieve greater precision?
16. Which group of measurements is the most precise? (The accepted value is 15.73 mL)
a) 15.76 mL, 15.88 mL, 15.93 mL
b) 15.23 mL, 15.74 mL, 15.96 mL
c) 15.43 mL, 15.47 mL, 15.49 mL
d) 15.14 g, 15.96 g, 15.99 g
17. The following values were recorded as the mass of products when a chemical reaction was
carried out three separate times: 8.83 g; 8.84 g; 8.82 g. The true mass of products from that
reaction is 7.01 g. The values are:
a) accurate, but not precise.
b) precise, but not accurate.
c) both accurate and precise.
d) neither accurate nor precise.
18. Indicate whether each of the following statements is true (T) or false (F).
a) ( ) Precision is a measure of the relation between an experimental result and the true
or accepted result.
b) ( ) The absolute error in a measurement is a better descriptor of error than the
relative error.
c) ( ) Systematic error causes the results to always be too high or too small
d) ( ) Proportional errors are independent of the size of the sample being analyzed.
e) ( ) The antilogarithm of 2.3776 is 2.386*102
19. Systematic errors can be removed by
a) Buying new instrument
b) Breaking the instrument
c) Dusting the instrument
d) Recalibrating the instrument
20. Which of the following is caused by careless handling?
a) Systematic error
b) Gross error
c) Random error
d) None of the mentioned