A gas sample containing only SO3, CH2O and C2H6O2 has the following mass percent composition: 65.1% SO3 and 8.79% CH2O. Calculate the partial pressure (torr) of SO3 if the total pressure of the sample is 4712 torr.


Unit conversion
K = C + 273
1 atm = 760 torr

Molar Mass (g/mol)
SO3 80.063
CH2O 30.026
C2H6O2 62.068

I would convert the percent composition of the gas to mole fractions, then

PSO3 = XSO3*Ptotal

I came up with 3461 torr, but the homework program I am using said that the correct answer is 2510 torr. So, I either did something wrong, or the method provided above does not work

To calculate the partial pressure of SO3, we need to first find the moles of SO3 in the gas sample.

1. Convert the mass percent composition of SO3 into grams.
Mass of SO3 = (Mass percent of SO3 / 100) * Total mass of the gas sample

Mass of SO3 = (65.1 / 100) * Total mass of the gas sample

2. Convert the grams of SO3 into moles using the molar mass of SO3.
Moles of SO3 = Mass of SO3 / Molar mass of SO3

3. Use moles of SO3 to calculate the partial pressure of SO3 using Dalton's law of partial pressures.
Partial pressure of SO3 = (moles of SO3 / total moles of all gases) * Total pressure of the sample

Let's calculate step by step:

Step 1:
Total mass of the gas sample = sum of the masses of all components
Given: Mass percent of SO3 = 65.1%
Calculate the mass percent of CH2O:
Mass percent of CH2O = 100% - Mass percent of SO3
Mass percent of CH2O = 100% - 65.1%
Mass percent of CH2O = 34.9%

Given: Total pressure of the sample = 4712 torr

Step 2:
Convert the mass percent of SO3 into grams.
Mass of SO3 = (65.1 / 100) * Total mass of the gas sample

Step 3:
Convert the grams of SO3 into moles using the molar mass of SO3.
Moles of SO3 = Mass of SO3 / Molar mass of SO3

Step 4:
Use moles of SO3 to calculate the partial pressure of SO3 using Dalton's law of partial pressures.
Partial pressure of SO3 = (moles of SO3 / total moles of all gases) * Total pressure of the sample

Let's plug in the values and calculate the partial pressure of SO3:

Step 1:
Mass of SO3 = (65.1 / 100) * Total mass of the gas sample

Step 2:
Moles of SO3 = Mass of SO3 / Molar mass of SO3

Step 3:
Calculate the Total mass of the gas sample:
Total mass of the gas sample = Mass of SO3 + Mass of CH2O + Mass of C2H6O2

Step 4:
Total moles of all gases = Moles of SO3 + Moles of CH2O + Moles of C2H6O2

Step 5:
Partial pressure of SO3 = (moles of SO3 / total moles of all gases) * Total pressure of the sample

Now, let's calculate the partial pressure of SO3 based on the given information.