Combustion of a 0.1595 g of menthol
(156 g/mol) produces .449 g of Carbon Dioxide and 0.184 g of Water. What is the formula of menthol?
I am really confused as to where to start. I converted the Carbon Dioxide and Water to moles and got .102 mol for both of them but now I don't know what to do with those values and figure out how oxygen factors into it.
Then if the moles of CO2 and H2O are the same, then there are twice as many moles of H as C in the methanol.
CnH2nOx we have so far. where n is some number, and x is another number.
Now consider the law of mass conservation (sum masses reactants=sum mass products). From that , you know how much O2, and the moles of O2 were required.
Now you are approaching then end. You need to know the moles of O coming from the menthol.
from the masses and moles of the products, you can determine the total moles of O in the products, subtract twice the moles of O2 as a reactant: what is left? the moles of O in methol.
Now compare that to the number n. You have that already (number C moles in CO2 = .102=n notice x then is some number times n.
Now you have the formula ratio n, 2n, x
divide all of those subscripts by n
CH2Ox/n
now, probably x/n is a fraction. find some number which multiplied by x/n is a whole number. That is the common ratio to make the subscripts whole number ratios. Look up the structure of menthol, is is something like C10H20O
It has several isomers.
Thank you!
To determine the formula of menthol, we need to analyze the combustion products and calculate the moles of carbon, hydrogen, and oxygen atoms.
Step 1: Calculate the moles of carbon dioxide (CO2) produced.
We have 0.449 g of CO2. The molar mass of CO2 is 44 g/mol.
moles of CO2 = mass / molar mass = 0.449 g / 44 g/mol = 0.0102 mol
Step 2: Calculate the moles of water (H2O) produced.
We have 0.184 g of H2O. The molar mass of H2O is 18 g/mol.
moles of H2O = mass / molar mass = 0.184 g / 18 g/mol = 0.0102 mol
Step 3: Analyze the combustion reactions.
Combustion reactions involve oxidation. In organic compounds like menthol, carbon is oxidized to carbon dioxide (CO2), and hydrogen is oxidized to water (H2O). We can write the balanced combustion reaction as follows:
C10H20O + O2 -> CO2 + H2O
Here, the coefficient in front of O2 represents the number of moles of oxygen required.
Step 4: Balance the equation for moles of carbon.
From the balanced equation, we see that 1 mol of menthol produces 1 mol of CO2. Therefore, the moles of carbon in 0.1595 g of menthol is also 0.0102 mol.
Step 5: Calculate the moles of hydrogen.
From the balanced equation, we see that 1 mol of menthol produces 2 mol of water (H2O). Therefore, the moles of hydrogen in 0.1595 g of menthol is 0.0102 mol × 2 = 0.0204 mol.
Step 6: Calculate the moles of oxygen.
Since menthol contains carbon, hydrogen, and oxygen, the remaining moles after subtracting the moles of carbon and hydrogen would represent oxygen atoms.
moles of oxygen = (moles of CO2) + (moles of H2O) - (moles of carbon) - (moles of hydrogen)
moles of oxygen = 0.0102 mol + 0.0102 mol - 0.0102 mol - 0.0204 mol = 0 mol
Step 7: Determine the ratio of atoms.
The ratios of carbon, hydrogen, and oxygen atoms in the compound can be calculated by dividing the number of moles by the lowest number of moles (which is 0.0102 in this case).
Carbon: 0.0102 mol / 0.0102 mol = 1
Hydrogen: 0.0204 mol / 0.0102 mol = 2
Oxygen: 0 mol / 0.0102 mol = 0
Step 8: Write the empirical formula.
The empirical formula of menthol is C1H2.
Based on this empirical formula, it is evident that the actual molecular formula of menthol is some multiple of the empirical formula. Additional steps would be required to determine the exact molecular formula with the given information.
To determine the formula of menthol, we can start by finding the number of carbon, hydrogen, and oxygen atoms present in the given data.
1. Convert the mass of carbon dioxide (CO2) and water (H2O) to moles:
- Carbon dioxide (CO2): Given mass = 0.449 g
Molar mass of CO2 = 12.01 g/mol (carbon) + 2 * 16.00 g/mol (oxygen) = 44.01 g/mol
Moles of CO2 = Given mass / Molar mass = 0.449 g / 44.01 g/mol = 0.0102 mol
- Water (H2O): Given mass = 0.184 g
Molar mass of H2O = 2 * 1.01 g/mol (hydrogen) + 16.00 g/mol (oxygen) = 18.02 g/mol
Moles of H2O = Given mass / Molar mass = 0.184 g / 18.02 g/mol = 0.0102 mol
We have found that both carbon dioxide and water are present in 0.0102 mol.
2. Determine the number of carbon atoms:
- From the balanced chemical equation for combustion, we know that for each mole of carbon dioxide produced, one mole of carbon is consumed. Thus, the number of carbon atoms in 0.0102 mol of carbon dioxide is also 0.0102 mol.
3. Determine the number of hydrogen atoms:
- Water has two hydrogen atoms per molecule. Therefore, the number of hydrogen atoms in 0.0102 mol of water is 0.0102 mol * 2 = 0.0204 mol.
4. Determine the number of oxygen atoms:
- In combustion, we can assume that all the oxygen required comes from the air. The equation for the combustion of menthol is:
Menthol + Oxygen → Carbon Dioxide + Water
From the given data, we calculated that 0.0102 mol of carbon dioxide and 0.0102 mol of water are produced. This means that the number of oxygen atoms required is twice the number of moles of carbon dioxide produced, which is 0.0102 mol * 2 = 0.0204 mol.
5. Calculate the ratio of C:H:O atoms:
- The ratio of carbon, hydrogen, and oxygen atoms in the formula can be determined by dividing the number of moles of each element by the smallest number of moles obtained (here, 0.0102 mol).
Carbon: 0.0102 mol / 0.0102 mol = 1
Hydrogen: 0.0204 mol / 0.0102 mol = 2
Oxygen: 0.0204 mol / 0.0102 mol = 2
6. Write the empirical formula:
- The ratio found in the previous step represents the empirical formula of menthol. In this case, the ratio is C1H2O2, which can be simplified as CHO2.
Therefore, the empirical formula of menthol is CHO2.