Question

Starting with the following equation:

P4(s) + F2(g) → PF3(g)

Calculate the moles of F2 that will be required to produce 27.5 grams of PF3.

a) 0.25 moles
b) 0.5 moles
c) 1 mole
d) 2 moles

Answer 1

To find the moles of F2 needed to produce 27.5 grams of PF3, convert the mass to moles, determine the stoichiometric ratio from the balanced equation, and calculate the moles of F2, which amount to approximately 0.5 moles.

Step-by-step explanation:

To calculate the moles of F2 required to produce 27.5 grams of PF3, you need to:

1. Determine the molar mass of PF3.
2. Convert the mass of PF3 to moles using this molar mass.
3. Use the stoichiometry of the balanced chemical equation to find the ratio of moles of F2 to moles of PF3.
4. Multiply the moles of PF3 by the ratio to find the moles of F2.

The balanced chemical equation is P4(s) + 6F2(g) → 4PF3(g). The molar mass of PF3 is approximately 88 g/mol, so 27.5 g of PF3 is equal to about 0.3125 moles (27.5 g ÷ 88 g/mol). From the equation, it takes 6 moles of F2 to produce 4 moles of PF3, which is a 3:2 ratio. Therefore, you need 0.3125 moles × (3/2) = 0.46875 moles of F2, which rounds to approximately 0.5 moles when considering significant figures.