Ch18 Chemical Analysis Characterizing Test Bank + Answers

Chapter 18: Chemical analysis: characterizing chemical compounds

Test Bank

Type: multiple response question

Title: Chapter 18 - Question 01

1) A chromatographic technique features which two of the following?

a. Liquid phase

b. Stationary phase

c. Mobile phase

d. Gas phase

e. Solid phase

Type: matching question

Title: Chapter 18 - Question 02

2) Match the size of the following compounds with the order in which they are collected during molecular exclusion chromatography.

Feedback: In a manner that may seem counter-intuitive at first, large compounds move most swiftly through the column because they cannot pass through the beads that make up the column. By contrast, smaller compounds can pass through the beads, and so travel further on their ‘journey’ through the column: a greater distance travelled equates to a longer time spent travelling. Look at Figure 18.6b, which depicts this.

a. Large = First

b. Medium = Second

c. Small = Third

Type: multiple response question

Title: Chapter 18 - Question 03

3) Which of the following statements regarding chromatography are true? Select all that apply.

a. The mobile phase may be a liquid or a gas.

b. The stationary phase is always a solid.

c. Separation on the basis of size is called affinity chromatography.

d. The fluid exiting the column is called the eluent.

e. During chromatography, the mobile phase passes over the stationary phase.

Type: multiple choice question

Title: Chapter 18 - Question 04

4) The length of time a compound takes to pass through a chromatographic column is called which one of the following?

a. The holding time

b. The release time

c. The repulsion time

d. The retention time

e. The separation time

Type: multiple response question

Title: Chapter 18 - Question 05

5) Which two of the following statements correctly describe gas-liquid chromatography?

a. The mobile phase is a liquid.

b. The mobile phase is a gas.

c. The stationary phase is a solid.

d. The stationary phase is a liquid.

e. The stationary phase is a gas.

Type: matching question

Title: Chapter 18 - Question 06

6) Rank the size of the following compounds according to the distance they travel through a gel during electrophoresis, with 1 = travels the furthest distance; 3 = travels the shortest distance.

Feedback: A large compound travels more slowly through the gel more slowly than does a smaller compound. Therefore, a large compound travels the shortest distance through the gel, and a small compound travels the furthest. See section 18.4 for more details about electrophoresis.

a. Large = 3

b. Medium = 2

c. Small = 1

Type: matching question

Title: Chapter 18 - Question 07

7) Match the following techniques with the attributes they exploit to effect separation.

Feedback: Compounds can be separated according to a number of different attributes. The important thing is to select the right technique for the attribute you’re looking to exploit. Look back through chapter 18 to remind yourself of the different properties of compounds that are exploited to effect separation.

a. Isoelectric focusing = Electrical charge

b. 2D-PAGE = Electrical charge and size

c. SDS-PAGE = Size

Type: multiple choice question

Title: Chapter 18 - Question 08

8) Which of the following statements about mass spectrometry is true?

a. The species being studied by mass spectrometry must carry a negative charge.

b. Mass spectrometry usually generates a mass spectrum with a single peak.

c. The molecular ion peak in a mass spectrum can be used to distinguish between structural isomers.

d. The sample being studied by mass spectrometry must be a vapour.

e. Isotopes of the same element generate the same peak in a mass spectrum.

Type: multiple choice question

Title: Chapter 18 - Question 09

9) The position of a peak in a ¹³C-NMR spectrum tells us information about which of the following?

a. The molecular mass of the sample being studied.

b. The atoms immediately surrounding a carbon atom.

c. The number of carbon atoms present in the sample.

d. The electrical charge carried by the sample.

e. The 3D structure of the sample being studied.

Type: multiple response question

Title: Chapter 18 - Question 10

10) Which of the following statements about NMR spectroscopy are true? Select all that apply.

a. The area under a peak in an NMR spectrum tells us about the number of atoms experiencing the same chemical environment.

b. NMR spectroscopy can be used to tell us about any elements in a compound.

c. An NMR spectrum tells us about the different isotopes of an element that are present in a compound.

d. NMR spectroscopy exploits light in the radiofrequency region of the electromagnetic spectrum.

Type: multiple choice question

Title: Chapter 18 - Question 11

11) Which of the following bonds vibrates at the highest frequency in an infrared spectrum? (Carbon has an atomic mass of 12; oxygen has an atomic mass of 16; hydrogen has an atomic mass of 1.)

a. C-H

b. O-H

c. C-O

d. C-C

e. O-O

Type: matching question

Title: Chapter 18 - Question 12

12) Rank the following bonds according to the wavelength of infrared light that they absorb, with 1 being the shortest wavelength, and 3 being the longest wavelength.

Feedback: Covalent bonds absorb infrared light with energies proportional to their strength: double bonds are stronger than single bonds, and triple bonds are stronger than double bonds. Therefore, double bonds absorb light of higher energy (shorter wavelength) than single bonds, and triple bonds absorb light of a higher energy than double bonds. See section 18.9 for more information.

a. C–O = 3

b. C≡C = 1

c. C=O = 2

Type: matching question

Title: Chapter 18 - Question 13

13) Rank the following wavenumbers according to the energy they represent, with 1 = highest energy, and 3 = lowest energy.

Feedback: Wavenumbers are the inverse of wavelengths – that is, a wavenumber = 1/λ. As the wavelength decreases (such that the light increases in energy) the corresponding wavenumber increases (as explained in section 18.9). So a large wavenumber represents more energy than a smaller wavenumber.

a. 2300 cm^{-1 =} 2

b. 1200 cm^{-1 =} 3

c. 4000 cm^{-1 =} 1

Type: matching question

Title: Chapter 18 - Question 14

14) Rank the following wavelengths according to the energy they represent, with 1 = highest energy, and 3 = lowest energy.

Feedback: The energy of electromagnetic radiation is inversely proportional to its wavelength – that is, energy with a long wavelength has less energy than energy with a short wavelength. For this question, we also need to remember the relative size of units – that one centimetre is 10^-2 metres, while one nanometre is 10^-9 metres. See chapter 2 for more details about the wavelength of electromagnetic radiation.

a. 1 cm ⁼ 3

b. 500 nm ⁼ 1

c. 750 nm ⁼ 2

Type: matching question

Title: Chapter 18 - Question 15

15) Match the techniques with the characteristics that they can be used to reveal.

Feedback: It is important to remember that different techniques are employed to tell us different things about a compound. Only by using a range of techniques can we fully characterize a given sample. Look back at chapter 18 for a reminder of the different experimental techniques available, and what each of them can tell us about a particular sample.

a. Mass of the sample = Mass spectrometry

b. 3-D structure = X-ray crystallography

c. Identity of functional groups attached to the hydrocarbon framework = Infrared spectroscopy

d. Nature of the hydrocarbon framework = NMR spectroscopy

Type: multiple choice question

Title: Chapter 18 - Question 16

16) Which of the following is not a type of bond vibration?

a. Wag

b. Scissor

c. Bend

d. Twist

e. Stretch

Type: multiple choice question

Title: Chapter 18 - Question 17

17) The parts of a compound that absorb strongly when exposed to ultraviolet light are called which of the following?

a. Chlorophylls

b. Chromatids

c. Chromophores

d. Chloroplasts

e. Photons

Type: true-false

Title: Chapter 18 - Question 18

18) A compound has a distribution ratio of 0.67. When mixed with organic and aqueous solvents, and the mixture allowed to settle, the compound is most likely to partition into the organic phase. True or false?

a. True

b. False

Type: multiple choice question

Title: Chapter 18 - Question 19

19) Centrifugation separates solid matter from the fluid in which it is suspended. What is the fluid called?

a. Solvent

b. Solute

c. Eluent

d. Sediment

e. Supernatant