Question

aluminium and oxygen react to produce aluminum oxide how many kg of aluminium oxide are formed when 5.4kg of aluminum reacts with excess oxygen​

Answer 1

The unbalanced reaction in question is

Al + O₂ → Al₂O₃

Let's balance it; let a, b, c be the coefficients in the reaction:

a Al + b O₂ → c Al₂O₃

Count up the atoms on either side for each element:

Al: a = 2c

O: 2b = 3c

Suppose c = 1; then

2b = 3c = 3 ⇒ b = 3/2

a = 2c = 2 ⇒ a = 2

So the balanced reaction is

2 Al + 3/2 O₂ → 1 Al₂O₃

or, using integer coefficients,

4 Al + 3 O₂ → 2 Al₂O₃

Now, we start with 5.4 kg of Al, which has molar mass of about 26.9815 g/mol. Convert the starting mass to moles:

(5.4 kg) (1000 g/kg) (1/26.9815 mol/g) ≈ 200.137 mol

In the balanced reaction, we have half as much Al₂O₃ produced for a given quantity of Al, so we end up with about 100.069 mol Al₂O₃ (molar mass ≈ 101.96 g/mol). Convert this amount to a mass:

(100.069 mol) (101.96 g/mol) (1/1000 kg/g) ≈ 10.203 kg ≈ 10. kg