A 1.325 g sample of an unknown vapor occupies 386 mL at 114 celsius and 946 mmHg. The simplest formula of the compound is NO2. What is the molecular formula of the compound?
(I have N2O4, is this correct and if not, why not? We never went over this type of question in class!
I would go with N2O4. Is that a guess or do you know how to work the problem?
To determine the molecular formula of the compound, we need to use the ideal gas law equation and compare the molar mass of the compound with the empirical formula mass. Let's go through the steps to find the correct molecular formula.
Step 1: Calculate the number of moles of the unknown vapor.
We can use the ideal gas law equation: PV = nRT
P = 946 mmHg (convert to atm by dividing by 760: 946/760 = 1.2447 atm)
V = 386 mL (convert to liters by dividing by 1000: 386/1000 = 0.386 L)
T = 114 °C (convert to Kelvin by adding 273.15: 114 + 273.15 = 387.15 K)
R = 0.0821 L·atm/(K·mol) (ideal gas constant)
Plugging the values into the equation:
(1.2447 atm) * (0.386 L) = n * (0.0821 L·atm/(K·mol)) * (387.15 K)
Solving for n (number of moles):
n ≈ 0.01895 mol
Step 2: Calculate the empirical formula mass of NO2.
The empirical formula mass gives the sum of the atomic masses in the empirical formula.
Empirical formula of NO2:
N = 14.01 g/mol
O = 16.00 g/mol (there are 2 oxygen atoms)
Empirical formula mass of NO2:
(14.01 g/mol) + (2 * 16.00 g/mol) = 46.01 g/mol
Step 3: Calculate the molecular formula mass of NO2.
To find the molecular formula, we need to know the ratio between the empirical formula mass and the molecular formula mass. The molecular formula mass should be an integer multiple of the empirical formula mass.
Molar mass of NO2:
N = 14.01 g/mol
O = 16.00 g/mol (there are 4 oxygen atoms)
Molecular formula mass of NO2:
(14.01 g/mol) + (4 * 16.00 g/mol) = 76.05 g/mol
Step 4: Determine the ratio between the empirical formula mass and the molecular formula mass.
Divide the molecular formula mass by the empirical formula mass:
76.05 g/mol ÷ 46.01 g/mol ≈ 1.65
Since the result is not close to an integer value, the empirical formula "NO2" is not the correct molecular formula. Therefore, "N2O4" is also not the correct answer.
To find the correct molecular formula, we need additional information or experimental data. The given information in the question is not sufficient to determine the exact molecular formula of the compound.