Paper: CSIR-NET June 2018 · Subject: Organic Chemistry · Chapter: Organic Spectroscopy · Topic: Organic Spectroscopy – General · Marks: 2 · Difficulty: Medium
Using a double beam UV-visible spectrophotometer, Beer's law fails for $\mathrm{K} \quad{ }_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}$ solution when
(a)Intensity of light source is changed
(b)Detector is not a photomultiplier tube
(c)Cuvette of 2cm size is used
(d)pH is not kept same in all measurements
Answer
Answer: D ✓ checked by 4AB · confidence high
Explanation
Chromate and dichromate interconvert with pH and absorb differently, so the absorbing species changes unless the pH is fixed — an apparent failure of Beer's law.