What mass of aluminum is formed by the decomposition of an electric current of 204 grams of aluminum oxide?

Given:

m (Al2O3) = 204 g

Find:

m (Al) -?

Solution:

2Al2O3 – (electric current) -> 4Al + 3O2, – we solve the problem using the composed reaction equation:

1) we find the amount of aluminum oxide contained in 204 grams of the substance:

n (Al2O3) = m: M = 204 g: 102 g / mol = 2 mol;

2) We compose a logical expression:

if 2 mol of Al2O3 gives 4 mol of Al,

then 2 mol of Al2O3 will give x mol of Al,

then x = 4 mol, – sometimes there can be a tautology in the calculation.

3) Find the mass of aluminum released during the reaction:

m (Al) = n * M = 4 mol * 27 g / mol = 108 g.

Answer: m (Al) = 108 g.