Final answer:
To calculate the mass in grams of 5.18 × 10¹⁵ molecules of Cs₂, we need to use the concept of molar mass and Avogadro's number. The molar mass of Cs₂ is 265.8109 g/mol, and after converting the number of molecules to moles, we can multiply by the molar mass to get the mass in grams.
Step-by-step explanation:
To calculate the mass in grams of 5.18 × 10¹⁵ molecules of Cs₂, we need to use the concept of molar mass. The molar mass of Cs₂ is 2 times the atomic mass of Cs because there are 2 Cs atoms in each molecule of Cs₂. The atomic mass of Cs is 132.90545 g/mol. So, the molar mass of Cs₂ is 2 * 132.90545 g/mol = 265.8109 g/mol.
Now, we can use the Avogadro's number (6.022 × 10²³) to convert from molecules to moles. We divide the given number of molecules by Avogadro's number to get the number of moles:
Number of moles = 5.18 × 10¹⁵ molecules / (6.022 × 10²³ molecules/mol) = 8.60 × 10⁻¹ mol
Finally, we multiply the number of moles by the molar mass to get the mass in grams:
Mass = 8.60 × 10⁻¹ mol * 265.8109 g/mol = 228.955 grams
Therefore, the mass in grams of 5.18 × 10¹⁵ molecules of Cs₂ is approximately 228.955 grams.