58. An excess of potassium ions makes KCl crystals appear violet or lilac in colour since ________.

(i) Some of the anionic sites are occupied by an unpaired electron.

(ii) Some of the anionic sites are occupied by a pair of electrons.

(iii) There are vacancies at some anionic sites.

(iv) F-centres are created which impart colour to the crystals.

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10 months ago

58. Options (i) and (iv) are correct since an excess of K+ ions make KCl crystals appear violet due to the defect called metal excess defect . The anionic vacancies are found to be created due to the movement of potassium atoms to the surface of the crystal when KCl is heated in an atmosphere of pot

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