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Organic Chemistry Questions and Answers – UV – Visible Spectroscopy | Organic Chemistry Multiple Choice Questions and Answers

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Free download in PDF Organic Chemistry Multiple Choice Questions and Answers for competitive exams. These short objective type questions with answers are very important for Board exams as well as competitive exams like UPSC, NDA, SSC etc. These short solved questions or quizzes are provided by Gkseries./p>

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(1) What is the wavelength range for UV spectrum of light?
[A] 400 nm – 700 nm
[B] 700 nm to 1 mm
[C] 0.01 nm to 10 nm
[D] 10 nm to 400 nm
Answer: 10 nm to 400 nm
(2) Which of the following comparison is correct for solvent shift on the n –>π* transition of acetone?
[A] H20 = CH30H = C2H50H = CHC13 = C6H14
[B] H20 > CH30H > C2H50H > CHC13 > C6H14
[C] H20 < CH30H < C2H50H < CHC13 < C6H14
[D] H20 > CH30H < C2H50H < CHC13 < C6H14
Answer: H20 < CH30H < C2H50H < CHC13 < C6H14

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(3) What is the correct order of λmax for n –> σ* transition?
[A] R-OH > R-NH2 > R-SH
[B] R-OH < R-NH2 < R-SH
[C] R-OH > R-SH > R-NH2
[D] R-OH < R-SH < R-NH2
Answer: R-OH < R-NH2 < R-SH
(4) What is the correct order of λmax for n –> π* transition for the R-CN, R-NO2, and R-N=N-R?
[A] R-CN < R-NO2 < R-N=N-R
[B] R-CN = R-NO2 = R-N=N-R
[C] R-CN > R-NO2 > R-N=N-R
[D] R-CN > R-NO2 < R-N=N-R
Answer: R-CN < R-NO2 < R-N=N-R
(5) What is the correct order of λmax for π –> π* transition for the following three compounds?
[A] R-C=C-R > R2C = CR2 > R-CHO
[B] R-C=C-R < R2C = CR2 < R-CHO
[C] R-C=C-R = R2C = CR2 = R-CHO
[D] R-C=C-R < R2C = CR2 >R-CHO
Answer: R-C=C-R < R2C = CR2 < R-CHO
(6) What is the correct order of λmax for n–> π* transition for the following three compounds?
[A] RCOOH > RCOOR’ > RCONH2
[B] RCOOH = RCOOR’ = RCONH2
[C] RCOOH = RCOOR’ < RCONH2
[D] RCOOH = RCOOR’ > RCONH2
Answer: RCOOH = RCOOR’ = RCONH2
(7) Which of the following is the correct order of λmax for n–> π* transition for the given compounds?

[A] 1>2>3>4>5
[B] 1<2<3<4<5
[C] 1>2<3>4<5
[D] 1>2>3<4>5
Answer: 1>2>3>4>5
(8) The ultraviolet spectrum of benzonitrile shows a primary absorption band at 224 nm. If a solution of benzonitrile in water, with a concentration of 1x 10-4 molar, is examined at a wavelength of 224 nm, the absorbance is determined to be 1.30. The cell length is 1 cm. What is the molar absorptivity of this absorption band?
[A] 2.3 x 104
[B] 3.3 x 104
[C] 1.3 x 104
[D] 4.3 x 104
Answer: 1.3 x 104
(9) The ultraviolet spectrum of benzonitrile shows a secondary absorption band at 271 nm. If a solution of benzonitrile in water, with a concentration of 1×10-4 molar solution is examined at 271 nm, what will be the absorbance reading ( ɛ = 1000) and what will be the intensity ratio, IO/I, respectively?
[A] 0.1, 1.26
[B] 0.2, 2.26
[C] 0.3, 3.26
[D] 0.4, 4.26
Answer: 0.1, 1.26
(10) Which of the following structural formula that is consistent with the following observations: An acid, C7H4O2Cl2 shows a UV maximum of 242 nm?

[A] (a)
[B] (b)
[C] (c)
[D] (d)
Answer: (c)

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