In nature, oxygen has three common isotopes. the atomic masses and relative abundances of these isotopes are given in the table below. isotope atomic mass (amu) relative abundance o-16          15.995                          99.759% o-17          16.995                              0.037% o-18          17.999                                0.204% calculate the average atomic mass of oxygen. show all of your calculations below.

Answer asap need by wednesday morning explain how a buffer works, using an ethanoic acid/sodium ethanoate system including how the system resists changes in ph upon addition of a small amount of base and upon addition of a small amount of acid respectively. include the following calculations in your i. calculate the ph of a solution made by mixing 25cm3 0.1m ch3cooh and 40cm3 0.1m ch3coo-na+. [ka = 1.74 x 10-5 m] ii. calculate the ph following the addition of a 10cm3 portion of 0.08 m naoh to 500cm3 of this buffer solution. iii. calculate the ph following the addition of a 10cm3 portion of 0.08 m hcl to 200cm3 of the original buffer solution.