Le dimanche 18 août 2013 01:30:14 UTC+2, Gregory Ewing a écrit : > wxjmfa...@gmail.com wrote: > > > Na + Cl --> NaCl > > > > > > the chemist combines *one mole* of sodium and *one > > > mole* of chlorine to get *one mole* of sodium chloride > > > > > > It's independent of the number of "particles" in a mole. > > > > The actual number chosen for the unit is arbitrary, but > > number of particles is still the central issue. The > > important thing is to have the *same* number of particles > > of Na and Cl. > > > > Weight only comes into it because it's totally impractical > > to count particles. And the particular number 6.02e23 is > > chosen because it happens to give a convenient relationship > > between number of particles and grams. If chemists had > > decided to use ounces instead, the number would be different. > > > > -- > > Greg
-------- "The actual number chosen for the unit is arbitrary, but number of particles is still the central issue." No. "The important thing is to have the *same* number of particles of Na and Cl." Yes. And it is precisely for that reason, a chemist works in "mole arithetic". Same reaction as above Na + Cl --> NaCl in pseudo math, with n = number of elements in a mole. n * Na + n * Cl --> n * NaCl <==> n * (Na + Cl) --> n * NaCl <==> division by n Na + Cl --> NaCl for any n. ---- The determination of n, the number of elements in a mole, is an indipendent and separate problem. (BTW, a very complicate task). jmf -- http://mail.python.org/mailman/listinfo/python-list
