Help! How would I answer the following chemistry questions?

Question

A) what’s the mass in grams of a sample of OF₂ containing 5.5e+23 fluorine atoms?

B) When hydrochloric acid reacts with aluminum metal it will produce diatomic hydrogen and aluminum(III) chloride. If 1.95 g of hydrochloric acid reacts with excess aluminum metal, what mass (in g) of aluminum(III) chloride would you expect to be produced?

Answer 1

A). First find the moles of OF₂ present

molar mass OF₂ = 54.0 g / mol

5.5x10²³ F atoms x 1 mol F / 6.02x10²³ F atoms x 1 mol OF₂ / 2 mol F = 0.457 mol OF₂

Next, convert this to g of OF2 using the molar mass

0.457 mol OF₂ x 54.0 g / mol = 24.7 g = 25 g (2 sig. figs)

B). Write the correctly balanced equation for the reaction taking place:

6HCl + 2Al ==> 2AlCl₃ + 3H₂

Since we have excess Al, the mols of HCl used will determine the mols of AlCl₃ produced

mols of HCl = 1.95 g HCl x 1 mol HCl / 36.5 g = 0.0534 mols HCl

mols AlCl₃ produced = 0.0534 mol HCl x 2 mol AlCl₃ / 6 mol HCl = 0.0178 mol AlCl₃

Use molar mass of AlCl₃ (133 g / mol) to convert to grams:

0.0178 mol AlCl₃ x 133 g / mol = 2.37 g AlCl₃ (3 sig.figs.)