Question #bb06f

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


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