Which of the following cations is detected by flame test?
Correct answer: B. K+
- A. NH4+
- B. K+
- C. Mg2+
- D. Al3+
Explanation
b) K+ (potassium ion):The potassium ion (K+) produces a characteristic lilac or violet flame color during a flame test. When a compound containing potassium is heated in a flame, the thermal energy excites the outermost electron of the potassium atom, and as it returns to its ground state, it emits energy in the form of light with a specific wavelength, resulting in the observed color.
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About Reactions of Group I Elements
Group I elements have one valence electron, so their reactivity increases down the group as ionisation energy decreases. Their reactions with water, oxygen, hydrogen and halogens produce hydroxides, oxides, hydrides and halides, while the behaviour of lithium differs from the heavier metals because of its small ionic size.
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