Question

Which of the following statements is/are CORRECT?

• A. Absorption occurs at all wavelengths if light passes through a given solution.
• B. The efficiency of a photochemical process is often expressed in terms of quantum yield.
• C. The unit of molar extinction coefficient is litre mole\(^{-1}\) cm.
• D. The extent of absorption in a dilute solution would be the same if the concentration is doubled and the path-length of light passing through solution is halved.

Hint:

The Beer-Lambert law relates absorbance to concentration and path length: \( A = \varepsilon c l \), where \( A \) is absorbance, \( \varepsilon \) is the molar extinction coefficient, \( c \) is concentration, and \( l \) is the path length.

Answer 1

The Correct Option is B, D

Step 1: Analyzing the options. 
(A) Absorption occurs at all wavelengths if light passes through a given solution: Incorrect — Absorption occurs at specific wavelengths corresponding to the energy levels of the molecules involved. 
(B) The efficiency of a photochemical process is often expressed in terms of quantum yield: Correct — Quantum yield is a measure of the efficiency of a photochemical reaction and is the ratio of the number of molecules reacting to the number of photons absorbed. 
(C) The unit of molar extinction coefficient is litre mole\(^{-1}\) cm: Incorrect — The molar extinction coefficient, also called molar absorptivity, is typically expressed in units of \( \text{L} \, \text{mol}^{-1} \, \text{cm}^{-1} \). 
(D) The extent of absorption in a dilute solution would be the same if the concentration is doubled and the path-length of light passing through solution is halved: Correct — According to Beer-Lambert law, absorbance is directly proportional to both the concentration of the solution and the path length. Doubling the concentration and halving the path length will result in the same absorbance. 
 

Step 2: Conclusion. 
The correct answers are (B) and (D).