Chemistry Forum

K₂Cr₂O₇ + KNO₂ + H₂SO₄ => Cr₂(SO₄)₃ + KNO₃ + H₂O + K₂SO₄
Can someone help me balance this chemical equation?

First start to find the redox pair
Cr₂O₇ 2- and Cr 3+
NO₂- and NO₃-
Condition is acidic or alcaline?

If acidic reduction requires H+ and release water. And oxidation is vise versa
If alcaline reduction requires water and release OH- , Oxidation vise versa.

Cr₂O₇ 2- + 14 H+ => 7H₂O + 2 Cr 3+
Balance charge
Cr₂O₇ 2- + 14 H+ + 6 e- => 7 H₂O + 2 Cr 3+

NO₂- + H₂O => NO₃- + 2 H+
Balance charge
NO₂- + H₂O => NO₃- + 2 H+ + 2 e-

LCD of electron is 6

Second equation multiply by 3
3 NO₂- + 3 H₂O => 3 NO₃- + 6 H+ + 6 e-

Addition
Cr₂O₇ 2- + 8 H+ + 3 NO₂- => 4 H₂O + 2 Cr₃+ 3 NO₃-

Finished

Add spectator ions

K₂Cr₂O₇ + 4 H₂SO₄ + 3 KNO₂ => 4 H₂O + Cr₂(SO₄)₃ + 3 KNO₃ + K₂SO₄