I need help with this problem...
A 1.208 g sample of a compound containing C, H, and O was burned to produce 2.561 g CO2 and 0.3930 g H2O. Calculate the empirical formula of the compound.
I always get stuck when it comes to finding the subscript for this compound.
Convert 2.561g CO2 to g C. Easiest done by 2.561 x (atomic mass C/molar mass CO2).
Convert 0.3930g H2O to g hydrogen. Easiest done by 0.3930 x (2*atomic mass H/molar mass H2O).
Then g O = 1.208 - g C - g H
Now convert g C, H, and O to moles.
moles = grams/molar mass.
Find the ratio of the elements to each other using whole numbers with the smallest being 1.00. That is easiest done by dividing the smallest number by itself; then divide the other mole amounts by the same small number.
If you have trouble, post your work and I can help guide you through it. Be sure to explain what you don't understand about the next step.
I ended up with C_2.809 H_2.106 O_1
so would that be C_3 H_2 O?
I would round that way BUT I didn't get those numbers. I ended up with 1.99 for C, 1.496 for H, 1.00 for O which rounds to C2H1.5O but that in small whole numbers is C4H3O2 if I didn't make a math error. Look over your work to see if you can find an error; post your work and I'll look for an error if you wish.
To find the empirical formula of the compound, we need to determine the ratio of moles of each element in the compound.
Let's start by calculating the number of moles of CO2 produced.
1. Find the molar mass of CO2.
- The molar mass of carbon (C) is 12.01 g/mol.
- The molar mass of oxygen (O) is 16.00 g/mol.
- So, the molar mass of CO2 is (12.01 g/mol × 1) + (16.00 g/mol × 2) = 44.01 g/mol.
2. Calculate the number of moles of CO2 produced.
- Divide the mass of CO2 produced (2.561 g) by the molar mass of CO2 (44.01 g/mol) using the formula:
Moles = Mass / Molar mass.
- Moles of CO2 = 2.561 g / 44.01 g/mol ≈ 0.058 mol.
Next, let's calculate the number of moles of H2O produced.
1. Find the molar mass of H2O.
- The molar mass of hydrogen (H) is 1.01 g/mol.
- The molar mass of oxygen (O) is 16.00 g/mol.
- So, the molar mass of H2O is (1.01 g/mol × 2) + (16.00 g/mol × 1) = 18.02 g/mol.
2. Calculate the number of moles of H2O produced.
- Divide the mass of H2O produced (0.3930 g) by the molar mass of H2O (18.02 g/mol) using the formula:
Moles = Mass / Molar mass.
- Moles of H2O = 0.3930 g / 18.02 g/mol ≈ 0.022 mol.
Now, we need to determine the ratio of moles of carbon (C), hydrogen (H), and oxygen (O).
3. Calculate the mole ratio.
- Divide the number of moles of each element by the smallest number of moles among them, which is 0.022 mol.
Moles of carbon (C) = 0.058 mol / 0.022 mol ≈ 2.64 ≈ 3 (approximated to the nearest whole number).
Moles of hydrogen (H) = 0.022 mol / 0.022 mol = 1.
Moles of oxygen (O) = 0.022 mol / 0.022 mol = 1.
4. Write the empirical formula.
- The empirical formula is the simplest whole number ratio of atoms in a compound.
- In this case, the empirical formula of the compound is C3H1O1, which can be simplified to C3H1O1 or just C3H1.
Therefore, the empirical formula of the compound is C3H1 or C3H.