You can determine the mole ratio between substances by comparing their coefficients in the balanced equation. Both Cl₂ and Br₂ have coefficients of 1. Therefore, they have a 1 to 1 (1:1) relationship.
If you were comparing the mole ratio of Cl₂ and NaBr, they would have a 1:2 relationship because Cl₂ has a coefficient of 1 and NaBr has a coefficient of 2.
