Hey, can someone help me with this?
A compound containing only C, H and O was subjected to combustion analysis. A sample of 6.120×10^-2 g produced 1.601×10^-1 g of CO2 and 5.243×10^-2 g of H2O. Determine the empirical formula of the compound and enter the appropriate subscript after each element.
C H O
Then they ask "If the molar mass of the compound is 252.354 g/mol, determine the molecular formula of the compound and enter the appropriate subscript after each element."
C H O
Is that 0.06120 g sample;
0.1601 g CO2 and 0.05243 g H2O? I may not be reading those funny symbols correctly.
Sorry, it's 0.06120 g produced 0.1601 g of CO2 and 0.05243 g of H2O
In order to find g oxygen you need to first convert CO2 to C and H2O to H.
g C = 0.1601 x (12.01/44) = ?
g H = 0.05243 x (2*1/18) - ?
g O = 0.06120 - g C - g H = ?
mols C = g C/12.01 = ?
mols H = g H/1 = ?
mols O = g O/16 = ?
Now find the ratio of these three elements to each other with the smallest number being no less than 1. The easy way to do that is to divide the smallest number by itself (that's the easy way to make it 1.00000); then divide the other numbers by the same small number. Round to whole numbers.
So I've done as you said and have come up with the following:
C (g) = 0.0437g
H (g) = 0.00583g
O (g) = 0.01167g
C(mol)=0.00364mol
H(mol)=0.00578mol
O(mol)=0.000729
I then divide for the ratio (Mm=m/n) and get 12 for C, 1 for H, and 16 for O, making the formula:
C12HO16, but it comes up as incorrect. Also, I was wondering where the 44 and 18 came from in your explanation:
g C = 0.1601 x (12.01/44) = ?
g H = 0.05243 x (2*1/18) - ?
Where am I going wrong here?
To determine the empirical formula of the compound, we need to calculate the number of moles of carbon, hydrogen, and oxygen in the given combustion analysis.
1. Start by calculating the moles of carbon:
- We know that the sample produced 1.601×10^-1 g of CO2.
- The molar mass of CO2 is 44.01 g/mol (12.01 g/mol for carbon and 32.00 g/mol for oxygen).
- To calculate moles, divide the mass of CO2 by its molar mass:
Moles of carbon = mass of CO2 / molar mass of CO2
= 1.601×10^-1 g / 44.01 g/mol
2. Next, calculate the moles of hydrogen:
- We know that the sample produced 5.243×10^-2 g of H2O.
- The molar mass of H2O is 18.015 g/mol (2.02 g/mol for hydrogen and 16.00 g/mol for oxygen).
- To calculate moles, divide the mass of H2O by its molar mass:
Moles of hydrogen = mass of H2O / molar mass of H2O
= 5.243×10^-2 g / 18.015 g/mol
3. Finally, calculate the moles of oxygen by subtracting the total moles of carbon and hydrogen from the total moles of the compound:
Moles of oxygen = Total moles of compound - (Moles of carbon + Moles of hydrogen)
Now that we have the moles of carbon, hydrogen, and oxygen, we can determine the empirical formula by dividing each by the smallest value.
4. Divide each mole value by the smallest mole value obtained in step 3.
- Round the resulting values to the nearest whole number (or simplest ratio).
- These whole numbers represent the subscripts of the elements in the empirical formula.
5. The resulting whole numbers represent the subscript of each element in the empirical formula of the compound.
For the molecular formula determination, we need to compare the empirical formula's molar mass with the given molar mass of the compound.
6. Calculate the molar mass of the empirical formula using the subscripts obtained in step 5.
7. Divide the given molar mass of the compound by the molar mass of the empirical formula:
Molecular formula multiplier = Given molar mass of the compound / Molar mass of the empirical formula
8. Multiply the subscripts in the empirical formula by the molecular formula multiplier to obtain the molecular formula.
By going through these steps, you can determine the empirical formula and the molecular formula of the compound.