Answer
5.15 x 10^22 molecules
Work Step by Step
We are given the Volume (2.25L), Temperature (37C) and the pressure (735 torr) so we can find the number of moles. First we convert the temperature to Kelvin by adding 273 so we have 310K and we convert the torr to atm as follows:
735 torr * (1 atm/ 760 torr) = 0.967 atm
Then we have PV = nRT and we are solving for n so we have:
n = PV/RT = (0.967 atm) * (2.25L) / (0.0821 * 310K) = 0.0855 mol
Then to find the number of molecules, we multiply by Avogadro's number 6.02 x 10^23 and we have:
5.15 x 10^22 molecules
