Final answer:
To find the mass of 6.34 x 10^27 formula units of KCl, calculate the number of moles and multiply by the molar mass of KCl. The result is 783,000 grams.
Step-by-step explanation:
The mass of 6.34 x 1027 formula units of KCl (potassium chloride) can be calculated by understanding the concept of moles and using the unified atomic mass unit (u). One mole of any substance contains Avogadro's number of entities (6.022 x 1023). First, we determine the molar mass of KCl, which is the sum of the atomic masses of potassium (K, 39.10 u) and chlorine (Cl, 35.45 u), totaling 74.55 u, or 74.55 grams per mole. Since the mass of one mole of a substance in grams is numerically equivalent to its formula mass in atomic mass units, we then calculate the number of moles in 6.34 x 1027 units.
Using the formula: Number of moles = (Number of formula units) / (Avogadro's number), we find that there are 6.34 x 1027 / 6.022 x 1023 = 1.05 x 104 moles of KCl. The mass can be found by multiplying the number of moles by the molar mass: Mass = (Number of moles) x (Molar mass of KCl), which yields 1.05 x 104 moles x 74.55 grams/mole = 7.83 x 105 grams, or 783,000 grams. Therefore, the mass of 6.34 x 1027 formula units of KCl is 783,000 grams.