In the reaction 5Br- + BrO3- + 6H+ giving 3Br2 + 3H2O, bromide ion is disappearing at 3.5 x 10^-4 M/s at some moment. At what rate is Br2 appearing?

1. Rates of different species are linked through the stoichiometric coefficients of the balanced equation. 2. Five bromide ions are consumed for every three Br2 molecules formed. 3. So the Br2 rate is 3/5 of the bromide rate. 4. Substituting gives 3/5 x 3.5 x 10^-4 mol per litre per second. 5. The product is 2.1 x 10^-4 M/s of Br2 appearing. 6. Sanity check: fewer Br2 form than Br- vanish, so the answer must be smaller than 3.5 x 10^-4 M/s. 7. The value 5.8 x 10^-4 M/s applies the factor 5/3 the wrong way round. 8. The value 3.5 x 10^-4 M/s assumes every species changes at the same rate, ignoring the coefficients. _Source: OpenStax Chemistry (CC BY 4.0), Ch 12 "Kinetics", section 12.1 Chemical Reaction Rates_