Name: Reaction Between Ferrous Ion and Potassium Dichromate
Uploaded: 2019-07-19
Duration: 4 min 21 s
Description: This video explains the excellent oxidising agent, potassium dichromate. One mole of potassium dichromate can oxidise six moles of ferrous sulphate molecules...

Question

Give equations to show the reactions between

CrO, {Cr}_{2} O_{3}

and

{CrO}_{3}

with aqueous acids and alkalis.

Accepted Answer

Chromium, is a d-block element, it exhibits a wide variety of oxidation numbers and its one or more oxides possess basic properties and some oxides exhibit only acidic properties. The higher the oxidation number the more acidic the corresponding oxide.

In $CrO$ , chromium is in ${Cr}^{+ 2}$ state and is basic in nature. It reacts with acid with the formation of salt and water.

$CrO + 2 HCl \to {CrCl}_{2} + H_{2} O$

${Cr}_{2} O_{3}$ , in $+ 3$ oxidation state is amphoteric in nature. It dissolve in acids, liberating hydrated chromium ions.

${Cr}_{2} O_{3} + HCl \to [Cr (H_{2} O)_{6}]^{+ 3} + {Cl}^{-}$

It dissolves in concentrated alkali to yield chromite ion.

${Cr}_{2} O_{3} + NaOH \to 2 {Na}^{+} + Cr {O_{2}}^{-} + H_{2} O$

${CrO}_{3}$ , in $+ 6$ oxidation state, is acidic in nature. This oxide on reaction with aqueous alkali forms tetrahedral chromate ion.

${CrO}_{3} + NaOH \to 2 {Na}^{+} + {CrO}_{4}^{- 2} + H_{2} O$

On dissolving chromium trioxide in strong acid following reaction occur.

${CrO}_{3} + 2 HCl \to {CrO}_{2} {Cl}_{2} + H_{2} O$

J. D. Lee Solutions for Chapter: Group 6 - the Chromium Group, Exercise 1: Exercise 1

J. D. Lee Chemistry Solutions for Exercise - J. D. Lee Solutions for Chapter: Group 6 - the Chromium Group, Exercise 1: Exercise 1

Questions from J. D. Lee Solutions for Chapter: Group 6 - the Chromium Group, Exercise 1: Exercise 1 with Hints & Solutions

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