## Problems and Solutions

to accompany

Chang's Physical Chemistry for the Chemical and Biological
Sciences

#### Helen O. Leung

Mount Holyoke 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.