How many grams of fluorine are needed to react with 8.5g of phosphorus?

Step 1: write the equation:

                                          P₄(s) + 6F₂(g) → 4PF₃(g) 

Step 2: Molar mass of P₄ = 30.97 g/mol × 4 = 123.88 g/mol

Step 3: Number of moles of phosphorus

                                                    n = m/M 

                                                    n = 8.5 g/123.88g/mol

                                                    n = 0.07 moles

Step 4: 0.07 × 12 = 0.84 moles of fluorine.

Fluorine is diatomic gas so we multiplied the number of moles by 12.

Step 5: To find the mass of fluorine we multiply the number of moles with the molar mass.

                            Mass of fluorine = 0.84 ×  228 

                                                        = 191.52 grams.