When 1 gram of sex hormone (contains C, H, and O) was burned in a combustion analysis, 1.5 grams of CO2 and 0.405 grams of H2O were obtained. The molar mass was found to be 352g/mol. What is the molecular formula for the sex hormone?
Convert 1.5 g CO2 to g C.
Convert 0.405 g H2O to g H.
Determine O by
1.00 g sample- gC - gH = g O.
Convert g each to moles.
moles C = g/atomic mass C.
moles H = g/atomic mass H.
moles O = g/atomic mass O.
Now find the ratio of the atoms to each other with the smallest number being 1.00. The easy way to do that is to divide the smallest number by itself; therefore, that number will be 1.00 and the other numbers will follow. Round to whole numbers (BUT don't round too much). If one of the numbers is further away than about 0.2 or so from a whole number, I would multiply the first set of numbers by 2, then 3, then 4, then 5, etc until all are reasonably close to whole numbers. That gives you the empirical formula.
To find the molecular formula, divide 352/mass empirical formula and round that answer to a whole number. That will be n in the following:
(CxHyOz)n where x,y,z are the subscripts in the empirical formula. Post your work if you need help through this. Be glad to help.
okay,this is what i have so far:
so is the chemical formula:
O2 + CxHyOz --> CO2 + H2O ?
CO2: 0.41 g of C
1.09 g of O2
H2O: 0.045 g of H2
0.36 g of O
Empirical Formula: CH2O -> n = 0.033 mol
C: 0.033 mol x 12g/mol = 0.396 g of C
H2: 0.033 mol x 2g/mol = 0.066 g of H2
O: 0.033 mol x 16g/mol = 0.528 g of O
is this right?
.41 (I used 0.409 since I'm allowed three places) is correct.
.045 g H is correct; not H2.
Then 1 - 0.409 - 0.045 = 0.546 g Oxygen.
Then 0.409/12 = ? moles C
0.045/1 =? moles H
0.546/16 = ? moles O.
Then continue.
To determine the molecular formula of the sex hormone, we need to use the given information about the combustion analysis. Let's break down the process step by step:
1. Find the number of moles of CO2 produced:
- The molar mass of CO2 is 44 g/mol (12 g/mol for carbon + 2 * 16 g/mol for oxygen).
- To find the number of moles of CO2, we divide the mass of CO2 by its molar mass:
Number of moles of CO2 = Mass of CO2 / Molar mass of CO2
Number of moles of CO2 = 1.5 g / 44 g/mol
2. Find the number of moles of H2O produced:
- The molar mass of H2O is 18 g/mol (2 * 1 g/mol for hydrogen + 16 g/mol for oxygen).
- To find the number of moles of H2O, we divide the mass of H2O by its molar mass:
Number of moles of H2O = Mass of H2O / Molar mass of H2O
Number of moles of H2O = 0.405 g / 18 g/mol
3. Determine the number of moles of carbon, hydrogen, and oxygen in the sex hormone:
- Since CO2 comes from carbon in the sex hormone, the number of moles of carbon in the sex hormone is the same as the number of moles of CO2.
- Since H2O comes from hydrogen in the sex hormone, the number of moles of hydrogen in the sex hormone is half the number of moles of H2O.
- The number of moles of oxygen can be calculated by subtracting the sum of carbon and hydrogen moles from the total number of moles obtained from the molar mass (352 g/mol):
Number of moles of oxygen = Total moles - Carbon moles - Hydrogen moles
Number of moles of oxygen = 352 g/mol - Number of moles of carbon - Number of moles of hydrogen
4. Convert the moles of each element to the empirical formula:
- Divide each number of moles by the smallest number of moles to calculate the mole ratio.
- Multiply the mole ratio by a whole number to obtain whole numbers for the empirical formula.
5. Determine the molecular formula:
- The empirical formula gives the simplest whole-number ratio of atoms, while the molecular formula gives the actual number of each type of atom.
- The molecular formula is a multiple of the empirical formula based on the molar mass given.
By following these steps and using the given data, you can find the molecular formula of the sex hormone.