How many molecules are in 1.0 L of O₂ at STP? How may grams of O₂?

Verified step by step guidance

1. Identify that the problem involves calculating the number of molecules and grams of O₂ at Standard Temperature and Pressure (STP).
2. Recall that at STP, 1 mole of any gas occupies 22.4 L. Therefore, determine the number of moles of O₂ in 1.0 L by using the formula: \( \text{moles of O}_2 = \frac{1.0 \text{ L}}{22.4 \text{ L/mol}} \).
3. Use Avogadro's number, \(6.022 \times 10^{23}\) molecules/mol, to calculate the number of molecules in the moles of O₂ obtained from the previous step.
4. To find the mass of O₂, use the molar mass of O₂, which is approximately 32.00 g/mol. Multiply the number of moles of O₂ by the molar mass to find the mass in grams.
5. Summarize the steps: Calculate moles from volume using STP conditions, convert moles to molecules using Avogadro's number, and convert moles to grams using the molar mass of O₂.

Key Concepts

Molar Volume at STP

At Standard Temperature and Pressure (STP), one mole of any ideal gas occupies a volume of 22.4 liters. This concept is crucial for converting between the volume of a gas and the number of moles, allowing us to determine how many molecules are present in a given volume.

Avogadro's Number

Avogadro's number, approximately 6.022 x 10²³, represents the number of molecules in one mole of a substance. This constant is essential for converting moles of a gas into the actual number of molecules, which is necessary for answering the first part of the question regarding the number of molecules in 1.0 L of O₂.

Molar Mass of O₂

The molar mass of O₂ (oxygen gas) is approximately 32 grams per mole, calculated from the atomic mass of oxygen. This concept is important for converting moles of O₂ into grams, which is needed to answer the second part of the question about how many grams of O₂ are present in 1.0 L at STP.