Question #bb06f

1 Answer
Apr 19, 2015

NTP, or Normal Temperature and Pressure, conditions imply a temperature of #20^@"C"#, or 293.15 K, and a pressure of 1 atm.

#T = "293.15 K"#
#P = "1 atm"#

Since you also know the volume the gas occupies under these conditions, you can easily solve for the number of moles present by using the ideal gas law equation, #PV = nRT#.

Once you know how many moles of oxygen gas you have, you can calculate the number of oxygen molecules by using the fact that 1 mole of any substance contains exactly #6.022 * 10^(23)# molecules of that substance - this is known as Avogadro's number.

So, start by figuring out he number of moles you have

#PV = nRT => n = (PV)/(RT)#

#n = (1cancel("atm") * 11.2cancel("L"))/(0.082(cancel("L") * cancel("atm")/("mol" * cancel("K")) * 293.15cancel("K"))) = "0.4659 moles "# #O_2#

This is equivalent to having

#0.4659cancel("moles") * (6.022 * 10^(23)"molecules")/(1cancel("mole")) = color(green)(2.81 * 10^(23)"molecules")#

Since oxygen is a diatomic molecule, i. e. it takes two oxygen atoms to make up an oxygen molecule, the number of oxygen atoms will be twice as big

http://science.jrank.org/kids/pages/140/Making-up-Molecules.html

#2.81 * 10^(23)cancel("molecules") * "2 atoms"/(1cancel("molecule")) = color(green)(5.62 * 10^(23)"atoms")#