OPR Meter or Oxidation Reduction Potential Meter is indicates the ratio between the solution’s ability to oxidize and reduce which this experiment use HOCl solution (bleach, Haiter™) 6% w/w by adding HOCl 1 ml of each to water 500 ml, then observed pH value and voltage (mV) when put the bleach and do this until the pH is not changed.
From experiment, when the bleach increased as a result, the pH and the voltage were increased which shows the number of negatively charged electrons in the water and is a measure of the oxidizing properties of disinfectants in water when negative ion of Cl increased as a result, the pH value and the voltage was increased also.
Redox reaction: HOCl (aq) + H+ + 2e- → Cl-(aq) + H2O
We can find concentration of HOCl from [HOCl] = (6/52.5) (x/1000) (1000/(1000+x))
Determine X is bleach add, 6 is concentration of bleach, and 52.5 is mass of HOCl