Gas reacts help plz

Question

Oxygen gas reacts with powdered aluminum according to the reaction:

4Al(s)+3O2(g)=2Al2O3(s)

How many liters of O2 gas, measured at 781 mm Hg and 27 C, are required to completely react with 2.4 mol of Al?

Answer 1

4Al(s) + 3O₂(g ==> 2Al₂O₃(s) ... balanced equation]

Using the stoichiometry of the balanced equation, we find the moles of O₂ gas needed:

2.4 mol Al x 3 mol O₂ / 4 mol Al = 1.80 mols O₂ needed

Next, we convert this to liters of O₂ using the ideal gas law, PV = nRT

P = pressure in atm = 781 mm Hg x 1 atm / 760 mm Hg = 1.03 atm

V = volume in L = ?

n = moles of O₂ = 1.80 mols

R = gas constant = 0.0821 Latm/Kmol

T = temperature in K = 27ºC + 273 = 300K

Solving for V we have...

V = nRT / P = (1.80)(0.0821)(300) / 1.03

V = 43 L (2 sig. figs.)