Measurement & data processing (First test)

1. Which are reduced when repeated measurements of a physical quantity are made?

A. both random and systematic errors

B. only systematic errors

C. only random errors

D. neither systematic nor random errors

2. An experiment was performed to find the enthalpy change for a reaction. It was repeated several times to give consistent results. However when the average of the results was compared to the literature value there was a large difference. Which is the
most likely explanation for this large difference?

A. both random and systematic errors

B. only systematic errors

C. only random errors

D. neither systematic nor random errors

3. Which of the following may cause systematic errors when used in an experiment?

I. A wrongly calibrated thermometer

II. A standard solution that has been prepared wrongly

III. Taking the reading from the top of the meniscus when using a pipette

A. I and II only

B. I and III only

C. II and III only

D. I, II and III

4. Before performing a titration a student rinsed all her apparatus with distilled water but did not dry it afterwards. Which will not affect the accuracy of her titration result?

A. Failure to rinse the burette with the solution it contains before filling it

B. Failure to rinse the pipette with the liquid it contains before filling it

C. Failure to dry the conical flask after washing with distilled water

D. Failure to thoroughly mix the contents of the volumetric flask before taking a sample by pipette

5. An experiment to determine the molar mass of a volatile liquid gave the result as 60 g mol^-1. The literature value is 56 g mol^-1. What was the experimental error expressed as a percentage?

A. 6.7%

B. 7.1%

C. 4%

D. 4.0%

6. A mixture of calcium carbonate and magnesium carbonate is prepared by mixing 8.36 g of calcium carbonate with 7.64 g of magnesium carbonate. The total mass of the mixture should be reported to x significant figures; the mass ratio of calcium carbonate
to magnesium carbonate should be reported to y significant figures , and the difference in mass between calcium carbonate and magnesium carbonate should be reported to z significant figures. What are the respective values for x, y and z?

A. 3, 3, 2

B. 4, 4, 3

C. 4, 3, 2

D. 3, 3, 3

7. A student used an analytical balance to measure the mass of a solid and the result as 0.020 g. How many significant figures are there in this value?

A. 1

B. 2

C. 3

D. 4

8. A student determined the empirical formula of magnesium oxide by heating a known mass of magnesium in air and weighing the product after the magnesium had burned. Which factors would result in her calculated formula having a higher ratio of magnesium
to oxygen than 1:1?

I. Not all the magnesium reacted.

II. Some of the product escaped before it was weighed.

III. Some of the product was magnesium nitride, Mg₃N₂.

A. I and II only

B. I and III only

C. II and III only

D. I, II and III

9. The graph below shows data for how the concentration of a reactant, A, varied over time during a chemical reaction.

Once the line of best fit has been drawn which of the following statements are true?

I. By extrapolation the concentration of A after 37 minutes can be deduced.

II. By interpolation the concentration of A after 23 minutes can be deduced.

III. The rate of the reaction does not depend upon the concentration of A

A. I and II only

B. I and III only

C. II and III only

D. I, II and III

10. The Arrhenius equation gives the relationship between the rate constant, k, and the absolute temperature, T, at which the reaction takes place. It can be expressed logarithmically as

ln k = -E_a/RT + ln A

where E_a represents the activation energy for the reaction, R represents the gas constant and A is a constant known as the Arrhenius constant. Which statement is true when a graph of ln k against I/T is plotted to give a straight line?

A. The activation energy can be obtained from the gradient and the Arrhenius constant can be obtained from the intercept.

B. The activation energy can be obtained from the intercept and the Arrhenius constant can be obtained from the gradient.

C. The gradient equals –E_a/RT.

D. The intercept equals A

11. Which type of transition is associated with radio waves?

A. nuclear spin

B. molecular vibrations

C. outer electrons

D. inner electrons

12. What is the index of hydrogen deficiency (IHD) of C₆H₁₀?

A. 0

B. 1

C. 2

D. 10

13. Which of the following organic compounds give three peaks in their ¹H NMR spectra (ignore the peak due to the reference sample)?

I. C(CH₃)₃Br

II. CH₃CH₂CHO

III. (CH₃)₂CHCOOH

A. I and II only

B. I and III only

C. II and III only

D. I, II and III

14. How many peaks does 2,2-dimethylpropane give in its ¹H NMR spectrum?

2,2-dimethylpropane

A. 1

B. 3

C. 4

D. 12

15. What is the ratio of areas under each peak in the ¹H NMR spectrum of 2-methylbutane, CH₃CH(CH₃)CH₂CH₃?

A. 1 : 2 : 3 : 3 : 3

B. 3 : 1 : 3 : 2 : 3

C. 1 : 3 : 3: 5

D. 1 : 6 : 2 : 3

16. Which formula is consistent for a compound that contains a line at m/z = 15 but does not contain a line at m/z = 29 in its mass spectrum?

A. HC(CH₃)₂CHO

B. C(CH₃)₃Cl

C. (CH₃)₂CHCH₂CH₃

D. CH₃(CH₂)₂CH₃

17. Which technique can best be used to determine that a compound contains a carbonyl group?

carbonyl group

A. Infrared spectroscopy.

B. ¹H NMR spectroscopy

C. Acid-base titration

D. Mass spectrometry

18. Which hydrocarbon contains 14.3% by mass of hydrogen and gives a molecular ion peak with an m/z value of 56 in its mass spectrum?

A. ethene

B. but-1-yne

C. butane

D. but-2-ene

19. Which compound shows a sharp absorption around 1700 cm^-1 in its infrared spectrum?

A. CH₃CH₂CHO

B. CH₃CH₂CH₂OH

C. CH₃CH₂CH₂NH₂

D. CH₃CHCHCH₃

20. Which compound has an index of hydrogen deficiency (IHD) of one and gives two peaks in its ¹H NMR spectrum?

A. CH₃CHCHCH₃

B. CH₂CH₂

C. CH₃CHCH₂

D. CH₃CH₂CH₂CH₃

Answers

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