Question

Balance the following basic solutions.

1. H⁺ + Cr2O7ˉ² + 6Fe⁺² → 2Cr⁺³ + H2O + 6Fe⁺³

Answer 1

$H^+ + Cr_2O_7^{2-}+ 6Fe^{2+} \to 2Cr^{3+} + H_2O + 6Fe^{3+}$

the chromium and iron molecules are balanced in the lhs and rhs

only the hydrogen ions are not balanced in this solution,

the total sum of ions in the lhs is 11+, the total sum of ions in the rhs is 24+

therefore 13+ more ions are needed in the lhs and the new balanced equation becomes;

$14H^+ + Cr_2O_7^{2-}+ 6Fe^{2+} → 2Cr^{3+} + 7H_2O + 6Fe^{3+}$

this balanced equation is in the acidic medium to turn it we had 14OH- to both sides

$14H_2O + Cr_2O_7^{2-}+ 6Fe^{2+} \to 2Cr^{3+} + 7H_2O + 6Fe^{3+} + 14OH^-$

eliminating H2O the balanced equation in the basic medium becomes

$7H_2O + Cr_2O_7^{2-}+ 6Fe^{2+} \to 2Cr^{3+} + 6Fe^{3+} + 14OH^-$