## Problems and Solutions to Accompany Chang’s Physical Chemistry for the Chemical & Biological Sciences

Helen O. Leung Amherst College

Mark D. Marshall Amherst College

### Sample Problem

It has been said that every breath we take, on average, contains molecules that were once exhaled by Wolfgang Amadeus Mozart (1756-1791). The following calculations demonstrate the validity of this statement. (a) Calculate the total number of molecules in the atmosphere. (b) Assuming the volume of every breath is 500 mL, calculate the number of molecules exhaled in each breath at 37°C, which is the body temperature. (c) If Mozart’s life span was exactly 35 years, what is the number of molecules he exhaled in that period? (Given that the average person breathes 12 times per minute). (d) Calculate the fraction of molecules in the atmosphere that were breathed out by Mozart. How many of Mozart’s molecules do we inhale with every breath of air? Round off your answer to one significant figure (e) List three important assumptions in these calculations.