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

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Answer 1 · 2016-01-30T19:20:57

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

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:

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

What is the mass of 7.9 * 10^237.9 * 10^23 of O_2O_2 at STP?