What is the mass of #7.9 * 10^23# of #O_2# at STP?

1 Answer
anor277
Jan 30, 2016

The mass of #7.9xx10^23# #O_2# molecules is INDEPENDENT of temperature and pressure. It is approx. #40# #g#.

Explanation:

Avogadro's number of #O_2# molecules has a mass of #32.00# #g#.

We have #7.9xx10^23# #O_2# particles; i.e.

#(7.9xx10^23" particles")/(6.022xx10^23" particles "mol^-1)# #=1.31# #mol#.

So we take this molar quantity, and multiply this by the molecular weight:

#1.31*molxx32.00*g*mol^-1# #=# #??? g#

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