edited bv: RON DELORENZO Middle Georgia College
Cochran. Georgia 31014
How Large Is a Mole? Irving R. Tannenbaum
Angeles College Culver City, CA 90230 Many techniques have been devised to demonstrate how enormously large a number Avogadro's number is.' We illustrate this to first-year chemistry students by assigning them the following problem, which is to be solved hy the unit-factor method: West LO$
exactly 1million dollars per second since that time. When did the money run out? If it did not run out, how muchremainsnow, after the passage of 4.5 billion years? The calculation gives the answer that the money has not yet run out. Indeed, after 4.5 billion years, a t the rate of 1 million dollars per second, only 0.24 mol of dollars have been given away! The students find this problem to be satisfying and are usually greatly impressed with the size of a mole.
A mole of dollars was created at the time that the Earth was formed, 4.5 billion years ago. It was given away at the rate of
Volume 67
Number 6
June 1990
481
