* Different Gases, Different Oxygen Content: The number of oxygen atoms in a given mass depends on the molecular formula of the gas. For example:
* Oxygen gas (O₂): Each molecule has two oxygen atoms.
* Carbon dioxide (CO₂): Each molecule has two oxygen atoms.
* Water vapor (H₂O): Each molecule has one oxygen atom.
Here's how to calculate the number of oxygen atoms if you know the gas:
1. Determine the molecular formula of the gas. This tells you how many oxygen atoms are in each molecule.
2. Calculate the molar mass of the gas. This is the mass of one mole of the gas, expressed in grams per mole (g/mol).
3. Convert the mass of the gas to moles. Divide the mass of the gas by its molar mass.
4. Multiply the number of moles by Avogadro's number. This will give you the number of molecules of the gas.
5. Multiply the number of molecules by the number of oxygen atoms per molecule. This will give you the total number of oxygen atoms.
Example:
Let's say you have 2.50 grams of carbon dioxide (CO₂).
1. Molecular formula: CO₂ (2 oxygen atoms per molecule)
2. Molar mass of CO₂: 44.01 g/mol (12.01 g/mol for C + 2 * 16.00 g/mol for O)
3. Moles of CO₂: 2.50 g / 44.01 g/mol = 0.0568 mol
4. Number of CO₂ molecules: 0.0568 mol * 6.022 x 10²³ molecules/mol = 3.42 x 10²² molecules
5. Number of oxygen atoms: 3.42 x 10²² molecules * 2 oxygen atoms/molecule = 6.84 x 10²² oxygen atoms
Therefore, there are approximately 6.84 x 10²² oxygen atoms in 2.50 grams of carbon dioxide.
