i'm not sure how correct this is please correct me if i'm wrong but there wouldnt be a change in mass as theres no gaseous products so nothing would be leaving the reaction so the mass would be the same. the iodine clock reaction is specific to iodine cause it measures the colour change of iodine and how fast it happens, but other reactions can have clock reactions to measure rate if your measuring colour change. it would just be called something else instead of iodine clock reaction. hope that helps