Question

Could someone please explain how to do this question? Thanks!

Select the balanced equation for the reaction of K2Cr2O7 and FeSO4 in an acidic aqueous solution: o a. 2 Select one: a. Cr20-2- +6Fe2+ = 2Cr3+ + 6Fe3+ b. 14H+ + Cr2O72- + 6Fe2+ → 2Cr3+ + 7H2O + 6Fe3+ c. 7H2+ + Cr20-2- + 6Fe2+ → 2Cr3+ + 7H2O + 6Fe3+ d. 14H+ + 2Cr20-2- + 6Fe2+ → 2Cr3+ + 7H2O + 6Fe3+ O e. 7H+ + Cr2O72- + 6Fe2+ → 2Cr3+ + 7H2O + 6Fe3+

Answer 1

Answer :- Potassium dichromate (K₂Cr₂O₇) acts as a powerful oxidising agent in acidic medium. When it is treated with dilute sulfuric acid, nascent oxygen is liberated according to the following equation:

K₂Cr​​₂O₇ + 4H₂SO₄ $\rightarrow$ K₂SO₄ + Cr₂(SO₄)₃ + 4H₂O + 3O

The reaction involves the reduction of Cr₂O₇^2- ions to Cr​​​​​​​³⁺ ions as shown:

Cr​​​​​​​​​​​​​​_{2​​​​​​​}O​​​​​​​_{7​​​​​​​​​​​​​​} ^2- + 14H⁺ + 6e^- $\rightarrow$ 2Cr³⁺ + 7 H₂O

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K​​​​​​​_{2​​​​​​​​​​​​​​​​​​​​​}Cr​​​​​​​_{2​​​​​​​}O₇  oxidizes ferrous salts (FeSO​​​​​​​​​​​​​​₄) to ferric salts as shown below:

K₂Cr₂O₇ + 4H₂SO₄ $\rightarrow$ K₂SO₄ + Cr₂(SO₄)₃ + 4H₂O + 3O

[ 2FeSO₄ + H₂SO₄ + O $\rightarrow$ Fe₂(SO₄)₃ + H​​​​​​​​​​​​​​₂O ] × 3

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K​​​​​​​​​​​​​​_{2​​​​​​​}Cr​​​​​​​_{2​​​​​​​}O₇ + 7H₂SO₄ + 6 FeSO₄ $\rightarrow$ K2SO4 + Cr2(SO4)3 + 3Fe₂ ​​​​​​(SO​​​​​​​₄)₃ + 7H₂O

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Or,

Cr₂O₇^2- + 14H⁺ + 6 Fe​​​​​​​²⁺ $\rightarrow$ 2Cr³⁺ + 6Fe³⁺ + 7H₂O