Question

Balance the chemical reactions using half reaction method:​

Answer 1

Write down the unbalanced equation

Step 2. Separate the redox reaction into half-reactions

a) Assign oxidation numbers for each atom

b) Identify and write out all redox couples in reaction

c) Combine these redox couples into two half-reactions

Step 3. Balance the atoms in each half reaction

a) Balance all other atoms except H and O

b) Balance the oxygen atoms with H2O

c) Balance the hydrogen atoms with H+

d) In a basic medium, add one OH- to each side for every H+

Step 4. Balance the charge with e-

Step 5: Make electron gain equivalent to electron loss in the half-reactions

Step 6: Add the half-reactions together

Step 7: Simplify the equation

Finally, check that the elements and charges are balanced

Sample redox equations

Acidic medium

$H2O2 = H2O + O2$

$Ca + Cl2 = CaCl2$

$Cu + HNO3 = Cu2+ + NO$

$SCN- + O2 = SO42- + HCO3- + NO3-$

$Zn + HNO3 = Zn(NO3)2 + NH4NO3$

$Fe2O3 + CO = Fe + CO2$

$P4 + HNO3 + H2O = H3PO4 + NO$

$Sb2S3 + H+ + NO3- = Sb2O5 + HSO4- + NO$

$Cr2O72- + H2C2O4 = Cr3+ + CO2$

$Mn2+ + S2O82- + H2O = MnO4- + HSO4-$

$MnO4- + SCN- = Mn2+ + HSO4- + NO3- + CO2$

$CH3CH2OH + Cr2O72- + H+ = CH3COOH + Cr3+$