One isotope of lead has 82 protons and 124 neutrons in its nucleus. what is the number of protons in the nucleus of any other isotope of lead?

Imagine that twenty i.u.’s of enzyme z were catalyzing the above reaction for one minute, under vmaxconditions, in a 3.00 ml assay volume. the assay is buffered with 20 mm phosphate buffer, ph 7.60. what will the ph be at the end of that one minute?