Answer:
0.408 moles
Step-by-step explanation:
The balanced chemical equation for the reaction of hydrofluoric acid (HF) with oxygen (O2) to form water (H2O) is:
4 HF + O2 → 2 H2O + 2 F2
From the balanced equation, we can see that the stoichiometric ratio of HF to H2O is 4:2 or 2:1. This means that for every 2 moles of H2O produced, 4 moles of HF must react.
To determine the amount of H2O that can be produced from 35 grams of HF and 5 liters (which we can assume to be at standard temperature and pressure) of O2, we first need to convert the volume of O2 to moles using the ideal gas law:
PV = nRT
where P is the pressure (which we can assume to be 1 atm at STP), V is the volume (5 L), n is the number of moles of gas, R is the ideal gas constant, and T is the temperature (273 K at STP).
n = PV/RT
n = (1 atm) x (5 L) / (0.08206 L atm/mol K x 273 K)
n = 0.204 moles of O2
Using the mole ratio between HF and H2O, we can calculate the theoretical yield of H2O:
4 HF + O2 → 2 H2O + 2 F2
4 mol HF / 1 mol O2 = x mol HF / 0.204 mol O2
x = 4 x 0.204 = 0.816 mol HF
Since we have 35 grams of HF, we can convert the mass of HF to moles using its molar mass:
Molar mass of HF = 1.01 g/mol (atomic mass of H) + 19.00 g/mol (atomic mass of F) = 20.01 g/mol
Moles of HF = Mass of HF / Molar mass of HF
Moles of HF = 35 g / 20.01 g/mol
Moles of HF = 1.749 moles
Since we have more HF than is required for the reaction (0.816 mol), HF is in excess and the amount of H2O that can be produced is limited by the amount of O2.
Using the mole ratio between O2 and H2O, we can calculate the theoretical yield of H2O:
4 HF + O2 → 2 H2O + 2 F2
1 mol O2 / 2 mol H2O = 0.204 mol O2 / x mol H2O
x = (2/1) x 0.204 = 0.408 mol H2O
Therefore, the theoretical yield of H2O is 0.408 moles.
Since we are asked to report the answer in moles, the number of moles of water that can be made is 0.408 moles.