Calculate the average atomic mass of antimony Antimony-121 has a mass of 120.904 amu and a natural % abundance 57.21
Antimony-123 has a mass of 122.904 amu and a natural % abundance of 42.79
can you give the work aswell trying to understand how to do it

Abeaker with 2.00×102 ml of an acetic acid buffer with a ph of 5.000 is sitting on a benchtop. the total molarity of acid and conjugate base in this buffer is 0.100 m. a student adds 4.70 ml of a 0.360 m hcl solution to the beaker. how much will the ph change? the pka of acetic acid is 4.740.