I have an exam in a day and I'm confused on how to solve this question. Do I use PV=nRT? Do I find out the molecular formula of the gas from the percentage of nitrogen and oxygen?
A sample of a mixture of gases contains 80.0% nitrogen gas and 20.0% oxygen gas by volume. Calculate the mass of 1.00 L of this mixture at STP.
I think the easiest (but the long) way is to say volume N2 = 0.8 x 1 L = 0.8 L
volume O2 = 0.2 x 1L = 0.2 L.
Then use PV = nRT and solve for n = mols N2 and mols O2.
Then mols N2 = grams/molar mass
and mols O2 = grams/molar mass. You know molar mass and mols, solve for grams each.
A second way is to find the molar mass of the gas that is 80% N2 and 20% O2.
That will be (0.8*28)+(0.2*32)=? g/mol and since 1 mol occupies 22.4L, then 1 L will be ?/22.4 = x?
I did both and obtained the same answer for both.
and ?/22.4
To solve this question, you do not need to use the Ideal Gas Law equation PV=nRT. Instead, you can use the concept of partial pressures and Dalton's Law of Partial Pressures.
Here's how you can solve the problem:
1. Identify the given information:
- The mixture contains 80.0% nitrogen gas and 20.0% oxygen gas by volume.
- The volume of the mixture is 1.00 L.
- The conditions are given as STP (Standard Temperature and Pressure).
2. Calculate the partial pressures:
- Since the partial pressure of each gas is directly proportional to its volume percentage in the mixture, you can calculate the partial pressures of nitrogen gas (PN2) and oxygen gas (PO2) based on their respective volume percentages.
- PN2 = 80.0% of the total pressure, and PO2 = 20.0% of the total pressure.
3. Calculate the total pressure:
- At STP, the total pressure is 1 atm.
4. Calculate the mass of the mixture:
- To calculate the mass, you need to use the ideal gas law equation PV = nRT.
- However, to use this equation, you need to know the molecular formula of the gas, which is not given in the question.
- Therefore, you cannot calculate the mass using the ideal gas law equation alone.
5. Additional information required:
- To calculate the mass of the mixture accurately, you need to know the molecular formula or molar mass of the gas or gases in the mixture.
- Without that information, it is not possible to determine the mass of the mixture.
As a suggestion, it would be best if you can find any additional information related to the molecular formula or molar mass of the gas or gases in the mixture to determine the mass accurately.