( S₂ O₃ )²⁻ + Sb O₅ => Sb O + H₂ S O₃
Sulphur oxide and Antimony pentoxide. => Antimony monoxide + Suphurous acid
Here on the products side, we have not any ions. It is possible that we have Hydrogen ions on the reactants side. Hydrogen ions are probably available through an aqueous solution.
It is not possible to balance this equation unless we know all the reactants.
x ( S₂ O₃ )²⁻ + y Sb O₅ + z H⁺ + w H₂ O => a * Sb O + b * H₂ S O₃
Balance Sulphur => b = 2x
antimony Sb => a = y
ionic charge => 2x = z
Hydrogen => 2x + 2 w = 2b = 4x => w = x
Balance oxygen now,
3x + 5 y + x = y + 6x => 4 y = 2 x => x = 2y
Choose y = 1,
2 ( S₂ O₃ )²⁻ + Sb O₅ + 4 H⁺ + 2 H₂ O ==> Sb O + 4 H₂ S O₃