In this lab, you will calculate the number of moles of air molecules inside a flask containing 20 mL of water by cooling the flask down to near 0°C and assuming the vapor pressure of water is negligible at that temperature. To do this, you will need to use the ideal gas law and the given information.
First, let's break down the steps:
1. Convert the volume of water from milliliters to liters:
- 20 mL = 0.02 L
2. Use the ideal gas law equation, PV = nRT, where:
- P is the pressure (in this case, the pressure of air inside the flask)
- V is the volume of air inside the flask (which is equal to the volume of the flask)
- n is the number of moles of air molecules
- R is the ideal gas constant (given as 8.314 J mol-1 K-1)
- T is the temperature in Kelvin
3. Rearrange the ideal gas law equation to solve for the number of moles of air molecules (n):
- n = PV / RT
4. Plug in the known values:
- P: Since the vapor pressure of water is negligible at near 0°C, we can assume the pressure inside the flask is equal to the atmospheric pressure, which is approximately 1 atm.
- V: The volume of the flask is given as 0.02 L.
- R: The ideal gas constant is given as 8.314 J mol-1 K-1.
- T: Convert the temperature from Celsius to Kelvin by adding 273.15. So, near 0°C is approximately 273.15 K.
5. Calculate the number of moles of air molecules using the equation n = PV / RT.
6. Provide the answer in the appropriate unit, moles.
By following these steps and plugging in the given values, you should be able to calculate the number of moles of air molecules inside the flask. Remember to use the correct units and pay attention to any assumptions made in the question.
Answer in 200 words