Explain the method of preparation of sodium dichromate from chromite ore . Give the equation representing oxidation of ferrous salts by dichromate ion.

Explain the method of preparation of sodium dichromate from chromite o

1.	Explain the method of preparation of sodium dichromate from chromite ore . Give the equation representing oxidation of ferrous salts by dichromate ion.
Answer» Potassium dischromate is prepared from chromite are `FeCr_2O4` in the following steps. Step : 1 : Preparation of sodium chromate `4FeCr_O_4+16NaOH +7O_2 rarr 8 NaCrO_4+2 Fe_2O_3+8H_2O` Step :2: Conversion of sodium chromate into sodium dichromate `2Na_2CrO_4+Conc.H_2SO_4rarr Na_2Cr_2O_7+Na_2SO_4+H_2 O` Oxidation of ferrous slats by dichromate ion `Cr_2O_7^(2-)+6Fe^(3+)+7H_2O`

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(i) Arrange the following compounds in an increasing order of basic strength : `C_(6)H_(5)NH_(2), C_(6)H_(5)N(CN_(3))_(2), (C_(2)H_(5))_(2)NH and CH_(3)NH_(2)` (ii) Arrange the following compounds in a decreasing order of `pK_(b)` values: `C_(2)H_(5)NH_(2), C_(6)H_(5)NHCH_(3), (C_(2)H_(5))_(2) NH and C_(6)H_(5)NH_(2)`
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Explain the method of preparation of sodium dichromate from chromite ore . Give the equation representing oxidation of ferrous salts by dichromate ion.

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