Final answer:
To find the number of molecules of octane in the flask, divide the mass of octane by its molar mass to calculate the number of moles, and then multiply by Avogadro's number to convert moles to molecules.
Step-by-step explanation:
Given that the conical flask contains 68.4 grams of octane, we can use the molar mass of octane to calculate the number of moles present. The molar mass of octane (C8H18) is the sum of the atomic masses of carbon and hydrogen.
Atomic mass of carbon (C) = 12.01 g/mol
Atomic mass of hydrogen (H) = 1.01 g/mol
Molar mass of octane = (8 * Atomic mass of carbon) + (18 * Atomic mass of hydrogen) = (8 * 12.01) + (18 * 1.01) = 99.34 g/mol
To find the number of moles, we can use the formula: number of moles = mass of substance / molar mass
Number of moles of octane = 68.4 g / 99.34 g/mol ≈ 0.688 mol
Since the molar ratio of molecules to moles is 6.02 x 1023, we can convert the number of moles of octane to the number of molecules by multiplying with Avogadro's number.
Number of molecules of octane = 0.688 mol * (6.02 x 1023 molecules/mol) = 4.03 x 1023 molecules