Question

How many grams of CO2 gas occupy 66.7 L at STP? Round your answer to 3 significant figures.
Note: Reference the Fundamental Constants table for additional information.

Answer 1

To determine how many grams of CO2 gas occupy 66.7 L at standard temperature and pressure (STP), we need to start with the properties of gases at STP.

At STP (0 degrees Celsius and 1 atm pressure), 1 mole of any ideal gas occupies 22.4 liters.

1. **Calculate moles of CO2:**
We can use the relationship between volume and moles:
\[
\text{Moles of CO2} = \frac{\text{Volume (L)}}{\text{Molar Volume (L/mol)}}
\]
\[
\text{Moles of CO2} = \frac{66.7 \, \text{L}}{22.4 \, \text{L/mol}} \approx 2.9768 \, \text{mol}
\]

2. **Find the molar mass of CO2:**
The molar mass of CO2 is calculated as follows:
- Carbon (C): 12.01 g/mol
- Oxygen (O): 16.00 g/mol (there are 2 oxygen atoms in CO2)

Thus,
\[
\text{Molar Mass of CO2} = 12.01 + (2 \times 16.00) = 12.01 + 32.00 = 44.01 \, \text{g/mol}
\]

3. **Calculate the mass of CO2:**
Now we can find the mass of CO2 using the number of moles and the molar mass:
\[
\text{Mass of CO2} = \text{Moles of CO2} \times \text{Molar Mass of CO2}
\]
\[
\text{Mass of CO2} = 2.9768 \, \text{mol} \times 44.01 \, \text{g/mol} \approx 130.90 \, \text{g}
\]

4. **Round the answer to three significant figures:**
\[
\text{Mass of CO2} \approx 131 \, \text{grams}
\]

Thus, the mass of CO2 gas occupying 66.7 L at STP is approximately **131 grams**.