**Introduction to Molecular Spectroscopy Quiz Answer. In this post you will get Quiz Answer Of Introduction to Molecular Spectroscopy**

## Introduction to Molecular Spectroscopy Quiz

## Offered By ”University of Manchester”

**Week- 1**

**UV/Vis laboratory quiz**

1.

Question 1

Run the UV/Vis spectrum of phenolphthalein at pH=1 and

pH=13 by clicking on the link below and then answer the following question.

Click here to run the UV/Vis spectrum of phenolphthalein. (The tool will launch in a new tab. Please return to this tab to answer the question).

Which of the following statements is INCORRECT?

1 point

**The absence of the band at 550 nm in the low pH****spectrum is caused by increased conjugation at that pH value.**- Phenolphthalein has increased conjugation at pH 13.
- Phenolphthalein is coloured at pH 13.
- The strong band at 240 nm is not responsible for the colour observed at

high pH.

2.

Question 2

Run the UV/Vis spectrum of litmus at pH =1 and pH = 13 by clicking on the link below and then answer the following question.

Click here to run the UV/VIS spectrum of litmus. (The tool will launch in a new tab. Please return to this tab to answer the question).

Which of the following statements is CORRECT?

1 point

- Litmus is colourless at pH = 1.
- Litmus appears blue at pH = 13 because it absorbs in the green region of the visible spectrum.
**The structure of Litmus is more conjugated at pH = 13.**- Litmus appears red at pH = 1 because off a strong absorption band at 240 nm.

**Week- 2**

**IR Lab Quiz**

1.

Question 1

Obtain the Infrared spectrum of phenol using the link below to open the spectral simulator in a new tab.

Click here to open Infrared spectrum of phenol. (The tool will launch in a new tab. Please return to this tab to answer the question).

Answer the following question: At what wavenumber values do the CH and CO stretching bands occur?

1 point

34003400 \text{cm}^{-1}cm−1and 530530 \text{cm}^{-1}cm−1

**3040 \text{cm}^{-1}cm−1and 1220 \text{cm}^{-1}cm−1**

34003400 \text{cm}^{-1}cm−1and 10601060 \text{cm}^{-1}cm−1

35203520 \text{cm}^{-1}cm−1and 15801580 \text{cm}^{-1}cm−1

2.

Question 2

Obtain the Infrared spectrum of propanal using the link below to open the spectral simulator in a new tab.

Click here to open Infrared spectrum propanal. (The tool will launch in a new tab. Please return to this tab to answer the question).

Answer the following question: At what wavenumber values do the CH and CO stretching bands occur?

1 point

17301730 \text{cm}^{-1}cm−1and 13501350 \text{cm}^{-1}cm−1

28302830 \text{cm}^{-1}cm−1and 17301730 \text{cm}^{-1}cm−1

28302830 \text{cm}^{-1}cm−1and 12001200 \text{cm}^{-1}cm−1

**2980 \text{cm}^{-1}cm−1and 1730 \text{cm}^{-1}cm−1**

29802980 \text{cm}^{-1}cm−1and 13501350 \text{cm}^{-1}cm−1

**Week- 3**

**NMR lab quiz**

1.

Question 1

Obtain the NMR spectrum of unknown A using the link below to open the spectral simulator in a new tab and then answer the following question:

Click here to view the NMR spectrum of unknown A. (The tool will launch in a new tab. Please return to this tab to answer the question).

Unknown A is an aromatic hydrocarbon liquid at room temperature having empirical formula C_{8}H_{10}C

8

H

10

From the spectral analysis, identify the structure as one of the following:

where red atoms=O, yellow atoms=C and blue atoms=H

1 point

Methylbenzene

**Ethylbenzene**

1,4-dimethylbenzene

Phenol

2.

Question 2

Obtain the NMR spectrum of unknown B using the link below to open the spectral simulator in a new tab and then answer the following question:

Click here to view the NMR spectrum of unknown B. (The tool will launch in a new tab. Please return to this tab to answer the question).

Unknown B is a colourless mobile liquid at RT with a sweet smell having empirical formula C_{4}H_{8}O_{2}C

4

H

8

O

2

From the spectral analysis, identify the structure as one of the following:

where red atoms=O, yellow atoms=C and blue atoms=H

1 point

**CH_{3}CH_{2}OCOCH_{3}CH3CH2OCOCH3**

CH_{3}CH_{2}CH_{2}COOHCH3CH2CH2COOH

CH_{2}CH(OH)CH_{2}COOHCH2CH(OH)CH2COOH

OHCH_{2}CH(OH)CHCH_{2}OHCH2CH(OH)CHCH2

**Week 4 Quiz**

1.

Question 1

Consider the two waves shown here representing electromagnetic radiation. The wavenumber of the blue wave is:

1 point

3.33.3 \times× 10^{7}107\text{cm}cm

3.33.3 \times× 10^{7}107\text{m}^{-1}m−1

3.33.3 \times× 10^{9}109\text{cm}^{-1}cm−1

**3.3 \times× 10^{7}107\text{cm}^{-1}cm−1**

2.

Question 2

The frequency of a transition is 5.45.4 \times× 10^{15}10

15

HzHz. What is the corresponding wavelength? [c=2.998[c=2.998 \times× 10^{8}10

8

mm \text{s}^{-1}s

−1

]

1 point

**5656 \text{nm}nm**

5.65.6 \times× 10^{-9}10−9\text{m}m

5.65.6 \times× 10^{-6}10−6\text{m}m

180,000180,000 \text{cm}^{-1}cm−1

3.

Question 3

The frequency of a transition is 3.13.1 \times× 10^{10}10

10

HzHz. What is the energy of this transition? [h =[h= 6.6266.626 \times× 10^{-34}10

−34

JJ s]s]

1 point

2.12.1 \times× 10^{-23}10−23\text{kJ}kJ

2.12.1 \times× 10^{-44}10−44\text{J}J

**2.12.1 \times× 10^{-26}10−26\text{kJ}kJ**

2.12.1 \times× 10^{-20}10−20\text{J}J

4.

Question 4

Which statement is correct?

1 point

Wavelength is directly proportional to frequency.

**Wavenumber is directly proportional to energy.**

Wavelength is directly proportional to energy.

Wavenumber is directly proportional to wavelength.

5.

Question 5

An absorption in an electronic spectrum is recorded at 17,00017,000 cm^{–1}cm

–1

. What does this correspond to in nmnm?

1 point

5.95.9 \text{nm}nm

5.95.9 \times× 10^{4}104\text{nm}nm

5.95.9 \times× 10^{9}109\text{nm}nm

**5.9 \times× 10^{2}102\text{nm}nm**

6.

Question 6

A shift to lower wavenumber for an absorption in a spectrum corresponds to:

1 point

a loss of intensity.

**a shift to lower frequency.**

a shift to higher energy.

a shift to lower wavelength.

7.

Question 7

According to the Beer-Lambert Law, on which of the following does absorbance NOT depend?

1 point

Distance that the light has travelled through the sample.

Solution concentration.

**Colour of the solution.**

Extinction coefficient of the sample.

8.

Question 8

A solution of XX of concentration 0.0100.010 molmol dm^{–3}dm

–3

gives an absorbance of 0.50.5. What concentration is a solution of XX which gives an absorbance reading of 0.250.25? Assume that the same optical cell is used for both readings.

1 point

0.0500.050 Math not terminated in text box

0.0200.020 Math not terminated in text box

0.0100.010 Math not terminated in text box

**.0050 Math not terminated in text box**

9.

Question 9

Compound ZZ absorbs light of wavelength 320320 nmnm. A 1.01.0 \times× 10^{–3}10

–3

molmol dm^{–3}dm

–3

solution of a compound ZZ gives an absorbance reading of 0.150.15 when placed in a solution cell of path length 11 cmcm. What is the value of the molar extinction (absorption) coefficient (\varepsilon)(ε) of ZZ?

1 point

1515 \text{dm}^{3}dm3\text{mol}^{–1}mol–1\text{cm}^{–1}cm–1

1.51.5 \times× 10^{–4}10–4\text{mol}mol \text{dm}^{–3}dm–3\text{cm}^{–1}cm–1

**150 \text{dm}^{3}dm3\text{mol}^{–1}mol–1\text{cm}^{–1}cm–1**

15001500 \text{dm}^{3}dm3\text{mol}^{–1}mol–1\text{cm}^{–1}cm–1

10.

Question 10

A solution of a compound absorbs light of wavelength 480480 nmnm, and for this absorption, the extinction coefficient is 1860018600 dm^{3}dm

3

mol^{–1}mol

–1

cm^{–1}cm

–1

. A sample of the dye of unknown concentration is placed in an optical cell of path length 11 cmcm and the absorbance reading is 0.180.18. What is the concentration of the solution?

1 point

2.02.0 \times× 10^{-8}10−8\text{mol}mol \text{dm}^{-3}dm−3

3.03.0 \times× 10^{-4}10−4\text{mol}mol \text{dm}^{-3}dm−3

0.0260.026 \text{mol}mol \text{dm}^{-3}dm−3

**9.7 \times× 10^{-6}10−6\text{mol}mol \text{dm}^{-3}dm−3**

11.

Question 11

A solution of compound ZZ absorbs light of wavelength 256256 nmnm, and for this absorption, log \varepsilonε == 3.33.3. What is the concentration of a solution of ZZ (in an optical cell of path length 11 cmcm) that gives the absorbance reading is 0.210.21?

1 point

2.42.4 \times× 10^{–3}10–3\text{mol}mol \text{dm}^{–3}dm–3

0.0640.064 \text{mol}mol \text{dm}^{-3}dm−3

**1.1 \times× 10^{-4}10−4\text{mol}mol \text{dm}^{-3}dm−3**

5.05.0 \times× 10^{-4}10−4\text{mol}mol \text{dm}^{-3}dm−3

12.

Question 12

A copper(II) sulfate solution of unknown concentration is placed in a colorimeter and an absorbance reading of 0.460.46 is recorded. Using the same solution cell, a 0.0550.055 ΜM solution of copper(II) sulfate gives an absorbance reading of 0.340.34. What is the concentration of the first solution?

1 point

2.42.4 \times× 10^{–3}10–3Math not terminated in text box

0.350.35 Math not terminated in text box

**.074 Math not terminated in text box**

0.0410.041 Math not terminated in text box

13.

Question 13

What best describes a chromophore?

1 point

A group of atoms in a coloured compound.

A coloured compound.

**A group of atoms in a compound responsible for the absorption of electromagnetic radiation.**

A group of atoms in a compound responsible for emission of electromagnetic radiation.

14.

Question 14

What does the notation \sigma^{\ast}\leftarrow nσ

∗

←n mean?

1 point

Emission; transition from a bonding orbital n to a \sigma^{\ast}σ∗\text{MO}MO.

**Absorption;transition from a non-bonding \text{MO}MO nn to a \sigma^{\ast}σ∗\text{MO}MO.**

Absorption; transition from a bonding orbital \text{n}n to a \sigma^{\ast}σ∗\text{MO}MO.

Emission;transition from a non-bonding \text{MO}MO nn toa \sigma^{\ast}σ∗\text{MO}MO.

15.

Question 15

How do values of \lambda_{max}λ

max

for the \pi^{\ast} \leftarrow \piπ

∗

←π transitions vary among a series of conjugated polyenes?

1 point

**Values shift to longer wavelength as the number of \text{C=C}C=C double bonds increases.**

Values shift to shorter wavelength as the number of \text{C=C}C=C double bonds increases.

Values vary but in no particular pattern.

Values vary very little.

16.

Question 16

Which electronic transition has the largest wavelength?

1 point

\pi^{\ast} \leftarrow \piπ∗←π

**\pi^{\ast} \leftarrow nπ∗←n**

\pi^{\ast} \leftarrow \sigmaπ∗←σ

\sigma^{\ast} \leftarrow \sigmaσ∗←σ

17.

Question 17

What is a red shift?

1 point

The shifting of an absorption to shorter wavelength.

**The shifting of an absorption to lower energy.**

The shifting of an absorption to higher energy.

The shifting of an absorption towards the blue end of the spectrum.

18.

Question 18

What is the relative intensity of an electronic \pi^{\ast}\leftarrow \piπ

∗

←π transition compared with an \pi^{\ast} \leftarrow nπ

∗

←n transition?

1 point

**Greater.**

Smaller.

The same.

Greater in the UV region and smaller in the UV.

19.

Question 19

Lycopene (\lambda_{max} = 469 nm)(λ

max

=469nm) is present in tomatoes. What colour of light does lycopene absorb?

1 point

**Blue.**

Red.

Yellow.

Orange.

20.

Question 20

A compound XX is characterized in its electronic spectrum by an absorption with \lambda_{max} = 217λ

max

=217 nmnm (\varepsilon_{max} =(ε

max

= 21 00021000 dm^{3}dm

3

mol^{–1}mol

–1

cm^{–1})cm

–1

). Of the compounds given below, XX is most likely to be:

1 point

water.

**buta-1,3-diene.**

ethanol.

\betaβ-carotene.

21.

Question 21

Which value is the correct reduced mass of ^{1}H^{19}F

1

H

19

F?

{Unified atomic mass unit u =u= 1.6611.661 \times× 10^{-27}10

−27

kgkg}

1 point

0.950.95 \text{kg}kg

1.7481.748 \times× 10^{-27}10−27\text{kg}kg

**1.58 \times× 10^{-27}10−27\text{kg}kg**

9.59.5 \times× 10^{-25}10−25\text{kg}kg

22.

Question 22

Which statement is incorrect

about CO_{2}CO

2

?

1 point

\text{CO}_{2}CO2has stretching modes of vibration.

\text{CO}_{2}CO2has one IR inactive stretching mode vibration.

**The IR spectrum of \text{CO}_{2}CO2can have a maximum of five absorptions.**

\text{CO}_{2}CO2 is linear.

23.

Question 23

Match the molecular formula to the number of degrees of vibrational freedom. Which pair is correct?

1 point

\text{D}_{2}\text{O}; 4D2O;4.

\text{CO}_{2}; 3CO2;3.

\text{CH}_{4}; 8CH4;8.

**\text{C}_{6}\text{H}_{6}; 30.C6H6;30.**

24.

Question 24

Hex-1-yneHex−1−yne is a hydrocarbon with a terminal H–C≡C– (alkyne)H–C≡C–(alkyne) group. The remaining part of the molecule contains CH_{2}CH

2

groups and a terminal CH_{3}CH

3

group. The IR spectrum of hex-1-ynehex−1−yne shows relatively strong absorptions at 3311, 2962, 2937, 28763311,2962,2937,2876 and 21202120 cm^{–1}cm

–1

as well as absorptions below 15001500 cm^{–1}cm

–1

. Which bands are assigned to the C≡CC≡C and terminal H–C(alkyne)H–C(alkyne) stretches?

1 point

**\text{C≡C}C≡C, 2120 \text{cm}^{–1}cm–1; \text{H C(alkyne)}HC(alkyne),3311 \text{cm}^{–1}cm–1**

\text{C≡C}C≡C, 29622962 \text{cm}^{–1}cm–1; \text{H–C(alkyne)}H–C(alkyne),33113311 \text{cm}^{–1}cm–1

\text{C≡C}C≡C, 21202120 \text{cm}^{–1}cm–1; \text{H–C(alkyne)}H–C(alkyne),28762876 \text{cm}^{–1}cm–1

\text{C≡C}C≡C, 33113311 \text{cm}^{–1}cm–1; \text{H–C(alkyne)}H–C(alkyne),21202120 \text{cm}^{–1}cm–1

25.

Question 25

For a nucleus with nuclear spin quantum number I = \frac{1}{2}I=

2

1

, what are the values of m_{I}m

I

?

1 point

**+\frac{1}{2}, -\frac{1}{2}+21,−21**

+\frac{1}{2}, +1+21,+10, +10,+1

+\frac{1}{2}, 0+21,0

26.

Question 26

Which list below gives only spin

active nuclei?

1 point

^{1}\text{H}1H, ^{2}\text{H}2H, ^{12}\text{C}12C

^{1}\text{H}1H, ^{12}\text{C}12C, ^{19}\text{F}19F

**^{1}\text{H}1H, ^{13}\text{C}13C, ^{19}\text{F}19F**

^{2}\text{H}2H, ^{12}\text{C}12C, ^{19}\text{F}19F

27.

Question 27

How many signals do you expect to see in the ^{1}H

1

H NMRNMR spectra of 2-bromopropane2−bromopropane (CH_{3})(CH

3

) _{2}CHBr

2

CHBr and 1-bromopropane1−bromopropane CH_{3}CH_{2}CH_{2}BrCH

3

CH

2

CH

2

Br?

1 point

1-\text{Bromopropane}: 2; 2-\text{bromopropane}:2.1−Bromopropane:2;2−bromopropane:2.

1-\text{Bromopropane}: 3; 2-\text{bromopropane}:3.1−Bromopropane:3;2−bromopropane:3.

1-\text{Bromopropane}: 2; 2-\text{bromopropane}:3.1−Bromopropane:2;2−bromopropane:3.

**1-\text{Bromopropane}: 3; 2-\text{bromopropane}:2.1−Bromopropane:3;2−bromopropane:2.**

28.

Question 28

A ^{1}H

1

H NMRNMR spectrum of compound CC contains a singlet, a triplet and a quartet. Which of the following compounds might CC be?

1 point

\text{CH}_{3}\text{CHClCHClCH}_{3}CH3CHClCHClCH3

\text{CH}_{3}\text{CH}_{2}\text{CHClCHCl}_{2}CH3CH2CHClCHCl2

\text{CH}_{3}\text{CH}_{2}\text{CH}_{2}\text{CHCl}_{2}CH3CH2CH2CHCl2

**\text{CH}_{3}\text{CCl}_{2}\text{CH}_{2}\text{CH}_{3}CH3CCl2CH2CH3**

29.

Question 29

A ^{1}H

1

H NMRNMR spectrum of CH_{3}CHBr_{2}CH

3

CHBr

2

shows two signals. What are the multiplicities and assignments of these signals?

1 point

**A quartet assigned to the \text{CH}_{3}CH3group and a doublet assigned to the\text{CH}CH group.**

A triplet assigned to the \text{CH}_{3}CH3 group and a singlet assigned to the \text{CH}CH group.

Two singlets, one assigned to each of the \text{CH}_{3}CH3and \text{CH}CH groups.

A doublet assigned to the \text{CH}_{3}CH3group and a quartet assigned to the \text{CH}CH group.

30.

Question 30

Protons in a high-field nuclear magnetic resonance spectrometer resonate at frequencies close to 800800 MHzMHz. Calculate the magnetic field strength of the spectrometer.

1 point

10.010.0 \text{T}T

12.012.0 \text{T}T

**18.8 \text{T}T**

21.221.2 \text{T}T