Solving Stoichiometry Problems

Question

Bauxite ore contains aluminum oxide, which is decomposed using electricity to produce aluminum metal. How many moles of aluminum metal can be produced if 100 g of oxygen is released?

Answer 1

First, we want to find the balanced equation for this reaction. The reaction equation for this would have aluminum oxide (Al₂O₃) being decomposed into aluminum (Al) and oxygen gas (O₂). So, we can balance the equation between the reactants and products to find that: 2Al₂O₃ --> 4Al + 3O₂.

We know that there is 100g of oxygen released, which means there is 100g of O_2. Using the periodic table, we know that the molar mass of O₂ must be 2 x 15.999 = 31.998 g/mol. So, if we have 100g of O₂, the # of moles = 100 g / 31.998 g/mol = 3.125 mol O₂.

Now, looking back at the balanced equation, we know that the mole ratio of Al to O2 is 4 Al : 3 O2 . Therefore, we can use the known amount of O2 to solve for the amount of Al we would have (I'll use the variable x here):

4/3 = x/3.125 --> x = (4/3)*(3.125) = 4.167 mol Al.

So we know 4.167 mol Al is released!