Question

The density of gaseous carbon dioxide is 1.977 g/L. If you have a 250.0 mL sample of carbon

dioxide, how many atoms of oxygen are contained within the sample?

Answer 1

density = 1.977 g/mL

volume = 250.0 mL

So,

mass of CO2 = density * volume

= 1.977 g/mL * 250.0 mL

= 494.25 g

Molar mass of CO2,

MM = 1*MM(C) + 2*MM(O)

= 1*12.01 + 2*16.0

= 44.01 g/mol

mass(CO2)= 494.25 g

number of mol of CO2,

n = mass of CO2/molar mass of CO2

=(494.25 g)/(44.01 g/mol)

= 11.23 mol

number of molecules of CO2 = number of mol * Avogadro’s number

= 11.23 * 6.022*10^23 molecules

= 6.763*10^24 molecules

1 molecules of CO2 has 2 atoms of O

So,

atoms of O = 2*number of molecules of CO2

= 2*6.763*10^24 atoms

= 1.35*10^25 atoms

Answer: 1.35*10^25 atoms