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In the flame test of a mixture of salts, a green flame with blue centre was observed. Which one of the following cations may be present?

1. Cu2+
2. Sr2+
3. Ba2+
4. Ca2+

Correct answer: Cu2+

Solution

A green flame with a blue centre is characteristic of copper, so Cu2+ is present. Ca2+ gives a brick-red flame, Sr2+ crimson, and Ba2+ apple-green without the blue centre.

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