Photo AI
A blue solution of copper(II) sulfate was investigated using colourimetry - HSC - SSCE Chemistry - Question 16 - 2022 - Paper 1
Question 16
A blue solution of copper(II) sulfate was investigated using colourimetry. Orange light (λ = 630 nm) was used and the pathlength was 1.00 cm. Which change would res... show full transcript
Worked Solution & Example Answer:A blue solution of copper(II) sulfate was investigated using colourimetry - HSC - SSCE Chemistry - Question 16 - 2022 - Paper 1
Step 1
Using blue light (λ = 450 nm)
Answer
Using blue light (λ = 450 nm) would increase the absorbance of copper(II) sulfate because the solution appears blue and absorbs orange light less efficiently. Blue light is complementary to orange and would facilitate better absorption as the molecules are better aligned to absorb this wavelength compared to the orange light used initially.
Step 2
Setting the pathlength to 2.00 cm
Answer
Changing the pathlength to 2.00 cm will also increase the absorbance since absorbance is directly proportional to the pathlength according to Beer-Lambert law, which states that absorbance (A) is given by the relationship:
where ε is the molar absorptivity, c is the concentration, and l is the pathlength. A longer pathlength will lead to greater absorbance.