A compound of carbon, hydrogen, and oxygen was burned in oxygen, and 2.00g of the compound produced 2.868 g CO2 and 1.567 g H2O. In another experiment, 0.1107 g of the compound was dissolved in 25.0 g of water. This solution had a freezing point of -0.0894 degrees C. what is the molecular formula of the compound?
Convert g CO2 to g C. 2.868 x (atomic mass C/molar mass CO2 = ?
Convert g H2O to H. 1.567 x (2*atomic mass H/molar mass H2O) = ?
2.00 - gC - gH = g O.
Convert g to mols.
mols = grams/atomic mass
Find the ratio of the elements to each other. This will give you the empirical formula. I came up with C3H8O3 BUT that doesn't make sense considering the molar mass. Check your post for accuracy, especially with the numbers.
You can see what I'm talking about with this.
delta T = Kf*m
Solve for m
m = mols/kg solvent.
Solve for mols.
mols = grams/molar mass
Solve for molar mass and I end up with about 26 which CAN'T possibly be right if the empirical formula is C3H8O3.
Isn't the molar mass 92.09 g/mol? This is what i got with /\T=Kf*m formula. If that's the case then C3H8O3 is the empirical formula and the molecular formula. Correct?
Yes, of course you are right. It was way past my bed time and I guess I just punched the wrong numbers on my calculator. The molar mass is 92 and not the 26 I initially calculated and that makes the C3H8O3 ok for the formula.
To find the molecular formula of the compound, we need to determine the empirical formula first, and then use the molar mass to find the molecular formula.
1. Calculating the empirical formula:
First, we need to calculate the number of moles of carbon, hydrogen, and oxygen in the products (CO2 and H2O) formed during the combustion:
- Moles of CO2 produced = mass of CO2 / molar mass of CO2
= 2.868 g / (12.01 g/mol + 2 * 16.00 g/mol)
≈ 0.1230 mol CO2
- Moles of H2O produced = mass of H2O / molar mass of H2O
= 1.567 g / (2 * 1.01 g/mol + 16.00 g/mol)
≈ 0.0875 mol H2O
Next, we need to find the number of moles of carbon, hydrogen, and oxygen in the empirical formula. We can assume that the number of moles of carbon and hydrogen in the compound is equal to the number of moles of carbon and hydrogen in the products.
- Moles of carbon = 0.1230 mol
- Moles of hydrogen = 0.0875 mol
To find the number of moles of oxygen, we need to subtract the sum of carbon and hydrogen moles from the total moles of the compound (0.1107 g/ molar mass of the compound):
- Moles of oxygen = (0.1107 g / molar mass of the compound) - (moles of carbon + moles of hydrogen)
2. Calculating the molar mass and molecular formula:
The molar mass of the compound can be calculated using the mass of the compound.
- Molar mass of the compound = mass of the compound / moles of the compound
= 0.1107 g / (moles of carbon + moles of hydrogen + moles of oxygen)
Finally, we can determine the molecular formula by dividing the molar mass of the compound by the empirical formula molar mass. The molecular formula will be a whole-number multiple of the empirical formula.
- Molecular formula = (molar mass of the compound) / (empirical formula mass)
By calculating the steps mentioned above, you should be able to determine the molecular formula of the compound.