How many moles are in 100 grams of oxygen?
The correct answer and explanation is:
Correct Answer:
There are 3.125 moles in 100 grams of oxygen (O₂).
Explanation:
To find the number of moles in a given mass of a substance, use the formula:
Moles = Mass (g) ÷ Molar Mass (g/mol)
In this case, the substance is oxygen gas, O₂. The molar mass of a single oxygen atom (O) is approximately 16 g/mol. Since oxygen gas exists naturally as a diatomic molecule (O₂), its molar mass is:
Molar mass of O₂ = 2 × 16 g/mol = 32 g/mol
Now, use the formula:
Moles = 100 g ÷ 32 g/mol = 3.125 moles
This result means that 100 grams of oxygen gas contain 3.125 moles.
Understanding the mole is essential in chemistry. A mole is a counting unit, similar to a dozen, but it refers to Avogadro’s number, which is approximately 6.022 × 10²³ entities (atoms, molecules, or particles). So, 1 mole of oxygen gas (O₂) contains 6.022 × 10²³ molecules of O₂ and has a mass of 32 grams.
Therefore, 3.125 moles of O₂ contain:
3.125 × 6.022 × 10²³ = 1.88 × 10²⁴ molecules of oxygen
This concept allows chemists to relate mass to number of particles, making it easier to perform chemical calculations and understand reaction proportions. When dealing with gases like oxygen, using moles helps determine how much of the gas is involved in reactions, how much product is formed, or how much gas is required. The mole bridges the microscopic world of atoms and molecules to the macroscopic world of grams and liters used in laboratories.