Step-by-step explanation:
There 6.022 * 10^23 particles in 1 mol of C₂H₆. Let's use this relationship to find the number of moles present in 6.9 * 10^24 particles of C₂H₆.
1 mol of C₂H₆ = 6.022 * 10^23 particles
moles of C₂H₆ = 6.9 * 10^24 particles * 1 mol of C₂H₆/(6.022 * 10^23 particles)
moles of C₂H₆ = 11.5 moles
Now that the we know the number of moles we can find the mass using the molar mass of C₂H₆.
molar mass of C = 12.01 g/mol
molar mass of H = 1.01 g/mol
molar mass of C₂H₆ = 2 * 12.01 g/mol + 6 * 1.01 g/mol
molar mass of C₂H₆ = 30.08 g/mol
mass of C₂H₆ = 11.5 moles * 30.08 g/mol
mass of C₂H₆ = 346 g
Answer: There are 346 g present.