Final answer:
To find the mass of fluorine reacting with 3.9 g of potassium, we calculate the moles of potassium, determine the stoichiometric amount of F2 needed, and then calculate the corresponding mass. Around 1.89 g of fluorine will react with the potassium.
Step-by-step explanation:
To calculate the mass of fluorine that reacts with 3.9 g of potassium (K), we will use the reaction equation provided: 2K + F2 → 2KF. From the periodic table, the molar mass of potassium (K) is 39.10 g/mol.
First, we calculate the amount of K in moles by dividing the mass of K by its molar mass:
Number of moles of K = rac{Mass of K}{Molar mass of K} = rac{3.9 g}{39.10 g/mol} = 0.0997 mol
Based on the reaction, 2 moles of K react with 1 mole of F2, so the moles of F2 needed is half the moles of K:
Number of moles of F2 = rac{0.0997 mol}{2} = 0.04985 mol
Next, we find the molar mass of F2, which is 19.00 g/mol × 2 = 38.00 g/mol. Now, we calculate the mass of F2:
Mass of F2 = Number of moles of F2 × Molar mass of F2 = 0.04985 mol × 38.00 g/mol = 1.8943 g
Therefore, 1.89 g of fluorine (rounded to three significant figures) will react with 3.9 g of potassium.