What is the volume occupied by #3.0*10^23# molecules of bromine gas at STP?

1 Answer
Kayla
Jul 19, 2016

#color(magenta)("11 L")#

Explanation:

#color(orange)("Because we are at STP, we will have to use the ideal gas law:")#
![slideplayer.com](useruploads.socratic.org)

At standard temperature and pressure, the temperature is 273K and the pressure is 1 atm.

Next, list your known and unknown variables. Our only unknown is the volume of #Br_2(g)#. Our known variables are P,R, and T.

We don't necessarily have #n# yet, but we're given a value that will lead us to the number of moles of bromine gas. All we have to do is convert molecules to moles using the conversion factor below:![www.slideshare.net](useruploads.socratic.org)

We'll use the second conversion factor because we can cancel out molecules and end up with moles:

#3.0xx10^(23)cancel"molecules"xx(1mol)/(6.02x10^(23)cancel"molecules")# #=# #0.498 mol#

Now all of the variables have good units! All that's left to do is rearrange the equation and solve for V like so:

#V = (nxxRxxT)/P#
#V = (0.498cancel"mol"xx0.0821(Lxxcancel"atm")/(cancel"mol"xxcancel"K")xx(273cancelK))/(1cancel"atm")#
#V = 11 L#

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