An isotope has three forms. 30% have a mass of 15 amu, 20% have a mass of 16 amu and 50% have a mass of 17 amu. What is the average atomic mass of this element?
a. 15.8 amu
b. 16.0 amu
c. 16.2 amu
d. 16.4 amu

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?