a student separated an unknown mixture of ions using the procedure of part a. when the spots were made…

a student separated an unknown mixture of ions using the procedure of part a. when the spots were made visible, a faint spot corresponding to cu²⁺ was seen. however, the student later learned that the unknown did not contain cu²⁺. which of the following could cause this result? a. the same spotting capillary was used to spot the cu²⁺ sample and the unknown sample. b. the cu²⁺ sample was contaminated with co²⁺ and fe³⁺. c. the chromatography paper was not trimmed to the correct dimensions. d. the position of the mobile - phase front was incorrectly marked. explain your answer:

a student separated an unknown mixture of ions using the procedure of part a. when the spots were made visible, a faint spot corresponding to cu²⁺ was seen. however, the student later learned that the unknown did not contain cu²⁺. which of the following could cause this result? a. the same spotting capillary was used to spot the cu²⁺ sample and the unknown sample. b. the cu²⁺ sample was contaminated with co²⁺ and fe³⁺. c. the chromatography paper was not trimmed to the correct dimensions. d. the position of the mobile - phase front was incorrectly marked. explain your answer:

Answer

Explanation:

Step1: Analyze chromatography - related errors

Chromatography involves proper sample - handling and marking. If the chromatography paper is not trimmed correctly, it can affect the movement of the mobile phase and the separation of components. If the mobile - phase front is incorrectly marked, it can lead to inaccurate calculations of retention factors and misinterpretation of the results.

Step2: Evaluate each option

  • Option a: Incorrect marking of the mobile - phase front can lead to errors in determining the position of the spots and the calculation of retention factors. This could explain why the expected Cu²⁺ spot was not seen as expected.
  • Option b: Contamination with Co²⁺ and Fe³⁺ would likely introduce additional spots rather than prevent the appearance of the Cu²⁺ spot.
  • Option c: Not trimming the paper to correct dimensions may affect the flow of the mobile phase, but it is less likely to specifically prevent the appearance of the Cu²⁺ spot compared to incorrect marking of the mobile - phase front.
  • Option d: Incorrect marking of the mobile - phase front is the most likely cause as it directly impacts the analysis of the spot positions.

Answer:

a. The position of the mobile - phase front was incorrectly marked.