Which of the following is a common source of experimental error when using flame tests to identify metal ions?

• A. The flame test always produces a unique color for every element
• B. Contamination of the sample with other metal ions
• C. The use of distilled water increases the accuracy of flame tests
• D. The inability of metal ions to emit light when heated

Answer: (B)

Verified step by step guidance

1. Understand the purpose of a flame test: it is used to identify metal ions based on the characteristic color they emit when heated in a flame.
2. Recognize that a common source of experimental error in flame tests is contamination, where traces of other metal ions mix with the sample and produce mixed or misleading colors.
3. Note that the statement 'The flame test always produces a unique color for every element' is incorrect because some elements can produce similar colors, and contamination can further complicate identification.
4. Consider that using distilled water helps reduce contamination but does not eliminate all sources of error, so it improves accuracy but is not the main source of error itself.
5. Understand that metal ions do emit light when heated, so the inability to emit light is not a source of error in flame tests.