A 2.5 gram sample of a hydrocarbon containing C, H, N, O is combusted in excess oxygen. The nitrogen compounds that are formed are treated to convert all of N to N2. The gases are passed through a CaCl2 drying tube which weighs 1.00 gram initially and 3.16 grams after the gases are passed through the tube. The remaining gas stream is bubbled into water where the CO2 is converted to H2CO3. Titration to equivalence requires 513mL of 0.4M NaOH. The O2 is removed by reacting with hot copper metal. The remaining N2 is collected in a 250mL container where it has a pressure of 1273 Hg at 25C. In a separate experiment, 36.5 grams of the compound is dissolved in 500 grams of CCl4 (Kf=29.8C/m) and the freezing point of the CCl4 is lowered 14.9%.

a- Determine the masses of C, H, N, O
b- Determine the empirical formula
c- Determine the molecular formula

I do not know where to start. Anything would be helpful. Thanks

P.S. don't forget the Related Questions below.

Sra

CaCl2 absorbs H2O (H2O comes from the H); the difference in mass is grams H2O. Convert that to grams hydrogen.

Carbon is converted to CO2 then to H2CO3 and titrated. From the titration data yu obtain grams C.

Use PV = nRT to solve for n for nitrogen and convert to grams.

Oxygen is obtained from 2.5 g minus the sum of the masses of C, H, N.

That gives you part a.
Part b.
Convert grams of each to moles (by dividing bv the atomic mass of the element), then find the ratio (in small whole numbers) of the elements to each other. The easy way to do that is to divide the smallest number by itself (making it 1.00) and dividing all of the other numbers by the same small number. That give you part b.

Part c.
Use delta T = Kf*m and solve for molality.

m = moles/kg solvent.
Solve for moles.

moles = grams/molar mass
solve for molar mass.

Thanks so much! Very thorough

To solve this problem, we need to break it down into smaller steps and analyze the given information. Let's go through each step one by one:

Step 1: Determine the mass of C, H, N, O.
We are given a 2.5g sample of the hydrocarbon. We need to determine the masses of carbon (C), hydrogen (H), nitrogen (N), and oxygen (O) in this sample.

Step 2: Determine the empirical formula.
The empirical formula gives the simplest whole number ratio of atoms in a compound. To determine the empirical formula, we need to use the molar masses of the elements and their respective masses in the compound.

Step 3: Determine the molecular formula.
The molecular formula gives the actual number of atoms of each element in a compound. To determine the molecular formula, we need to compare the molar mass of the empirical formula to the molar mass of the compound provided in a separate experiment.

Let's start by calculating the masses of C, H, N, and O.

Step 1: Determine the mass of C, H, N, and O.
We are given a 2.5g sample of the hydrocarbon. We need to determine the mass of carbon (C), hydrogen (H), nitrogen (N), and oxygen (O) in this sample.

Given information:
- Mass of hydrocarbon sample = 2.5g
- Weights of CaCl2 drying tube:
- Initial weight = 1.00g
- Final weight after gases passed through = 3.16g

To determine the mass of C, H, N, and O, we need to consider the different compounds that are formed during the combustion process.

During the combustion, the nitrogen compounds are treated to convert all of N to N2. This means that any nitrogen compounds in the sample are ultimately converted to N2 gas. The remaining gases after combustion are passed through the CaCl2 drying tube to remove any water vapor. The change in weight of the drying tube (3.16g - 1.00g) indicates the mass of water vapor removed.

The remaining gas stream, after water vapor is removed, is bubbled into water where the carbon dioxide (CO2) formed during combustion is converted to carbonic acid (H2CO3). Then, titration with NaOH is performed to determine the amount of H2CO3 formed.

Finally, the oxygen (O2) is removed by reacting with hot copper metal, leaving only nitrogen gas (N2). The pressure of the collected N2 gas in a 250mL container is given as 1273 Hg at 25°C.

To determine the masses of C, H, N, and O in the original hydrocarbon sample, we need to consider the following:

1. The difference in weight of the CaCl2 drying tube (3.16g - 1.00g) indicates the mass of water vapor (H2O) removed. The molar mass of water (H2O) is 18.015 g/mol, so we can calculate the moles of H2O removed.
moles of H2O = mass of H2O / molar mass of H2O

2. The amount of carbon dioxide (CO2) formed during combustion can be determined using the titration data with NaOH. From the volume and molarity of NaOH used in the titration, we can calculate the moles of CO2.
moles of CO2 = volume of NaOH (L) * molarity of NaOH (mol/L)

3. The mass of carbon (C) in the original hydrocarbon sample can be calculated from the moles of CO2 formed and the molar mass of carbon dioxide (CO2).
mass of C = moles of CO2 * molar mass of CO2

4. The remaining gas after removing water vapor and CO2 is N2. The pressure of N2 gas and its volume can be used to calculate the number of moles of N2 using the ideal gas law, PV = nRT.
moles of N2 = (pressure of N2 / pressure constant) * (volume of N2 / temperature)

Now that we have the number of moles of C, H, N, and O, we can calculate their masses using their respective molar masses.

Please provide the molar masses of C, H, N, and O, and any additional measurements if available, to proceed with the calculations.