## How to Balance Redox Equations

Sulphuric Acid is reduced by Iodide ions to form Sulphur Dioxide and Iodine. Reduction Half Equation H2SO4 ----------> SO2 1. Balance the species that have been oxidised or reduced. In this case the sulphur has been reduced from +6 to +4. The sulphur atoms are balance. 2. Balance the oxygen atoms using water There are 4 on LHS and 2 on RHS so add 2 H20 to the RHS H2SO4 ----------> SO2 + 2 H2O 3. Balance hydrogen atoms with H+ There are 2 on LHS and 4 on RHS so

## Limiting Reagents

If you have worked out the MOLES of two reactants then the limiting reagent is the one with less moles. Sorted? Well, it depends. If the reactants are in a 1:1 ratio then the above is true. But if the ratio is not equal then I'm afraid it's a bit more complicated. Let's say reactants A and B have a ratio of 2:1 in the balanced equation. If we have 0.02 moles of A and 0.015 moles of B which is the limiting reagent? If we start with A we can see from the ratio that 0.02 moles