UV- Visible spectroscopy Principal and Factor affecting absorption in UV-Visible Spectroscopy Multiple Choice Questions Answers

UV-VISIBLE SPECTROSCOPY PRINCIPAL :-

•  The principle is based on the measurements of spectrum of a sample containing atom/molecules.
• Spectrum is a graph of intensity of absorbed or emitted radiation by sample vs frequency or wavelength.
• Spectrometer is an instrument design to measure the spectrum of a compound.
• UV-Visible spectroscopy measure the response of a sample to ultra Violet and visible range of EMR.
• Molecules have either σ,π and n electron.

These electron absorbed uv radiation and under goes transition from ground state to excited state.

Factor affecting absorption in uv-visible spectroscopy :-

1. Absorption compound :-

It is increase absorption of UV. Example is Chromophore and Auxochrome

2. Solvent effect :-

Solvent that absorbed uv radiation are avoid.

Example is benzene , carbon tetrachloride, chloroform etc.

3. Temperature :-

Low temperature is suitable for uv visible spectroscopy.

In,High temperature absorption of UV radiation is increase.

4. Inorganic material :-

Inorganic material are increase the absorption.

Ex. Ag, Au etc.

ABSORPTION AND INTENSITY SHIFT :-

1. Bathochromic shift :- when absorption maximum of a compound shift to longer wavelength, it is known as Bathochromic shift or red shift.
2. Hypsochromic shift:- when absorption maximum of a compound to a shorter wavelength it is called a Hypsochromic shift or Blue shift.
3. Hyperchromic shift :- when absorption intensity of a compound is increased it is known as hyperchromic shift.
4. Hypochromic shift :- when absorption intensity of compound is decreased it is called hypochromic shift.

MCQ

Q1.

Sentence A: if temp. Is increases  UV radiation absorption is increase.

Sentence B: If temp. Is increases it is give better result in uv.

A. Sentence A and B is false.

B.  Sentence A and B is true.

C. A is true and B is false.

D. A is false amd B is true.

2. Which sentence is false about UV SPECTROSCOPY ?

A. Benzene is not used as solvent.

B. Low temperature is give better result in uv SPECTROSCOPY.

C. Chloroform is used as solvent in UV.

D. UV ray wavelength is 200- 400 nm.

3. Which sentence is true according to  UV-VISIBLE SPECTROSCOPY ?

A.The principle is based on the measurements of spectrum of a sample containing atom/molecules.

B.UV-Visible spectroscopy measure the response of a sample to ultra Violet and visible range of EMR.

C.Spectrometer is an instrument design to measure the spectrum of a compound.

D. All of the above

4. Which sentence is false about inorganic compound ?

A. Ag is increase  absorption of UV radiation.

B. AU is increase absorption of UV radiation.

C. Inorganic compound are decreased uv radiation absorption.

D.Inorganic compound are increased uv radiation absorption.

5.when absorption intensity of compound is decreased it is called

A. Red shift

B. Blue shift

C. Hypochromic shift

D. Hyperchromic shift

6. Which compound is increased uv absorption ?

A. Auxochrome

B. Chromophore

C. Inorganic compound

D. All of the above

7. If solvent is polar ans electron transition is n->π∗ which type of shift are seen in graph ?

A. Hypso chromich shift

B. Red shift

C. Blue shift

D. A and C

8.If solvent is non polar ans electron transition is n->π ∗which type of shift are seen in graph ?

A. Hypso chromich shift

B. Red shift

C. Blue shift

D. A and C

9.If solvent is non polar ans electron transition is  π⇒π∗which type of shift are seen in graph ?

A. Hypso chromich shift

B. Red shift

C. Blue shift

D. A and C

10. If solvent is  polar  electron transition is  π⇒π∗which type of shift are seen in graph ?

A. Hypso chromich shift

B. Red shift

C. Blue shift

D. A and C

Answer key

1.C

2.C

3.D

4.C

5.C

6.D

7.D

8.A

9.B

10.D

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