Why first ionisation enthalpy of Cr is lower than that of Zn ?
The electronic configuration of Cr and Zn is given below
Cr – [Ar] 3d5 4s1
Zn – [Ar] 3d10 4s2
Removing an electron from a half-filled 4s orbital requires lesser energy than removing an electron from a fully filled stable 4s orbital.
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When a chromite ore (A) is fused with sodium carbonate in free excess of air and the product is dissolved in water, a yellow solution of compound (B) is obtained. After treatment of this yellow solution with sulphuric acid, compound (C) can be crystallised from the solution. When compound (C) is treated with KCl solution, orange crystals of compound (D) crystallise out. Identify compounds A to D and also explain the reactions.
An oxide of mangnese (A) is fused with KOH in the presence of an oxidizing agent and dissolved in water. A dark green solution of compound (B) is obtained. Compound (B) disproportionates in neutral or acidic solution to give purple compound (C). Alkaline solution of (C) oxidises potassium iodide solution to a compound (D) and compound (A) is also formed. Identify compounds A to D and also explain the reactions involved.
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