John Roger's Stephens left a 3.5 kg iron shovel outside through the winter. The shovel now orange with rust, is rediscovered in the spring. It's mass is 3.7kg. How much oxygen combined with the iron?
To determine how much oxygen combined with the iron, we need to calculate the difference in mass before and after rusting.
The mass of the shovel before rusting is 3.5 kg.
The mass of the shovel after rusting is 3.7 kg.
Thus, the increase in mass is 3.7 kg - 3.5 kg = 0.2 kg.
This increase in mass is attributed to the oxygen that combined with the iron atoms during the rusting process.
To determine how much oxygen combined with the iron, we need to calculate the mass of the iron that has reacted with oxygen to form rust. The increase in mass of the shovel (from 3.5 kg to 3.7 kg) represents the mass of the rust, which is the result of the iron combining with oxygen.
First, we subtract the initial mass of the shovel (3.5 kg) from the final mass of the shovel (3.7 kg) to find the increase in mass:
Increase in mass = Final mass - Initial mass
Increase in mass = 3.7 kg - 3.5 kg
Increase in mass = 0.2 kg
Next, we need to assume that this increase in mass is entirely due to the combination of iron with oxygen. Rust is formed when iron reacts with oxygen in the air. The chemical formula for rust is Fe2O3, which means that for every two atoms of iron, three atoms of oxygen are required.
The molar mass of iron (Fe) is approximately 55.85 g/mol, and the molar mass of oxygen (O) is approximately 16.00 g/mol.
To calculate the amount of oxygen that combined with the iron, we need to convert the increase in mass from kg to g, then divide it by the molar mass of iron and multiply by the ratio of oxygen to iron in rust:
Mass of oxygen = (Increase in mass in g) x (1 mol Fe / 55.85 g Fe) x (3 mol O / 2 mol Fe) x (16.00 g O / 1 mol O)
Let's substitute the values and calculate:
Mass of oxygen = (0.2 kg × 1000 g/kg) × (1 mol Fe / 55.85 g Fe) × (3 mol O / 2 mol Fe) × (16.00 g O / 1 mol O)
Mass of oxygen ≈ 18.137 g
Therefore, approximately 18.137 grams of oxygen have combined with the iron to form rust on the shovel.