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CBSE Class 12 Chemistry Solved Question Paper 2015

Short Answer Type

1. Zn²⁺ salts are white while Cu²⁺ salts are coloured. Why?

Element/Ion	Electronic Configuration
Zn	3d¹⁰ 4s²
Zn²⁺	3d¹⁰
Cu	3d¹⁰ 4s¹
Cu²⁺	3d⁹

The colours of salts of transition metals are due to the d-d transition that depends on the presence of incompletely filled d-orbitals. Zn²⁺ has completely filled d-orbitals (3d¹⁰), while Cu²⁺ has incompletely filled d-orbitals (3d⁹); therefore, d-d transition is possible in Cu²⁺, which imparts colour to copper (II) salts.

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How much charge is required for the reduction of 1 mol of Zn²⁺ to Zn?

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Write the dispersed phase and dispersion medium of butter.

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Write the structures of the following molecules:
(i) H₂SO₃
(ii) XeOF₄

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5. Write down the IUPAC name of the complex [Pt(en)₂Cl₂]²⁺. What type of isomerism is shown by this complex?

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Using IUPAC norms write the formulate for the following coordination compounds:

(i) Hexaamminecobalt (III) chloride
(ii) Potassium tetrachloridonickelate (II)

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Define rate of reaction? Write two factors that affect the rate of reaction.

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Arrange the following in increasing order of their basic strength:

(i) C₆H₅ – NH₂, C₆H₅ – CH₂ – NH₂, C₆H₅ – NH – CH₃

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Why does a solution containing non-volatile solute have higher boiling point than the pure solvent? Why is elevation of boiling point a colligative property?

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