Thermite is a mixture of iron(III) oxide and aluminum powders that is used in some countries to weld railroad tracks. It is a spectacular reaction to yield solid aluminum oxide that floats on the molten iron. When cooled, the iron is ground smooth and even with the rest of the rail.
Fe2O3 + 2 Al 2 Fe + Al2O3
(a) How many grams of iron form when 114 g of aluminum reacts?
(b) How many atoms of aluminum react for every 2.20 g of aluminum oxide formed?
To answer these questions, we need to use stoichiometry, which is the calculation of the quantities of reactants and products in a chemical reaction.
(a) How many grams of iron form when 114 g of aluminum reacts?
To find the number of grams of iron formed, we need to use the balanced chemical equation and convert the given mass of aluminum into moles. Let's start with the balanced equation:
Fe2O3 + 2 Al → 2 Fe + Al2O3
From the equation, we can see that 2 moles of aluminum are required to form 2 moles of iron. Now, we need to find the molar mass of aluminum. Aluminum has an atomic mass of 26.98 g/mol.
So, the number of moles of aluminum is given by:
moles of aluminum = mass of aluminum / molar mass of aluminum
= 114 g / 26.98 g/mol
≈ 4.225 mol (rounded to three decimal places)
According to the balanced equation, 2 moles of aluminum yield 2 moles of iron. Therefore, the number of moles of iron produced is also 4.225 mol.
Now, we need to find the mass of iron using its molar mass. The molar mass of iron is 55.845 g/mol.
mass of iron = number of moles of iron × molar mass of iron
= 4.225 mol × 55.845 g/mol
= 235.7 g (rounded to one decimal place)
Therefore, when 114 g of aluminum reacts, approximately 235.7 g of iron is formed.
(b) How many atoms of aluminum react for every 2.20 g of aluminum oxide formed?
In this question, we are given the mass of aluminum oxide and we need to find the number of aluminum atoms that react to produce it.
First, we need to find the number of moles of aluminum oxide. Aluminum oxide (Al2O3) has a molar mass of 101.96 g/mol.
moles of aluminum oxide = mass of aluminum oxide / molar mass of aluminum oxide
= 2.20 g / 101.96 g/mol
= 0.0216 mol (rounded to four decimal places)
Now, from the balanced equation, we know that 2 moles of aluminum oxide are produced from 2 moles of aluminum. Therefore, the number of moles of aluminum involved in the reaction is also 0.0216 mol.
To find the number of atoms, we need to multiply the number of moles by Avogadro's number (6.022 x 10^23 atoms/mol).
number of atoms of aluminum = moles of aluminum × Avogadro's number
= 0.0216 mol × 6.022 x 10^23 atoms/mol
= 1.303 x 10^22 atoms
Therefore, approximately 1.303 x 10^22 atoms of aluminum react to produce 2.20 g of aluminum oxide.