The molar mass (formula weight) of carbon dioxide (CO2) is 44.01 g/mol.
At STP (Standard Temperature and Pressure), which is defined as 0°C (273.15 K) and 1 atm of pressure, 1 mole of any gas occupies 22.4 L of volume.
Now, we have 3.9 x 10^23 molecules of CO2:
- To find the number of moles, we divide the number of molecules by Avogadro's number:
n = N/Na = 3.9 x 10^23/6.022 x 10^23 = 0.648 moles
- To find the mass, we multiply the number of moles by the molar mass:
mass = n x M = 0.648 mol x 44.01 g/mol = 28.52 grams
Therefore, the mass of 3.9 x 10^23 molecules of carbon dioxide gas at STP is approximately 28.6 grams (option A).