A sample of a compound containing only carbon and hydrogen atoms is completely combusted, producing 66.0g of CO2 and 36.0g of H2O. What is the empirical formula?
To determine the empirical formula of the compound, we need to find the ratio of carbon to hydrogen atoms.
First, we can calculate the number of moles of CO2 and H2O produced:
moles of CO2 = 66.0g / 44.01 g/mol = 1.50 mol
moles of H2O = 36.0g / 18.02 g/mol = 1.998 mol
Next, we can simplify the mole ratio by dividing both by the smaller value:
moles of CO2 / 1.50 = 1
moles of H2O / 1.50 = 1.332
The ratio of carbon to hydrogen atoms in the compound can be expressed as:
C : H = (moles of CO2 / 1.50) : (moles of H2O / 1.50)
C : H = 1 : 0.888
We can simplify the ratio by multiplying both sides by a common factor of 9 to get whole numbers:
C : H = 9 : 8
Therefore, the empirical formula of the compound is C9H8.
but there are 2 H atoms in every H2O molecule
I get like' 20 * 2 H / 15 C = 40 H/15 C = 8 H/3C = C3H8
You are correct! Thank you for catching that mistake. The molecular formula should be reduced to the empirical formula by dividing each subscript by the greatest common factor.
In this case, the ratio of moles of carbon dioxide to water is 1:1.332, so the empirical formula is C3H8, which represents a compound called propane.
To determine the empirical formula of the compound, we need to find the simplest whole number ratio of carbon to hydrogen atoms in the compound.
Step 1: Calculate the number of moles of CO2.
Using the molar mass of CO2 (44.01 g/mol), we can calculate the number of moles:
Moles of CO2 = Mass of CO2 / Molar mass of CO2
= 66.0 g / 44.01 g/mol
≈ 1.5 mol
Step 2: Calculate the number of moles of H2O.
Using the molar mass of H2O (18.02 g/mol), we can calculate the number of moles:
Moles of H2O = Mass of H2O / Molar mass of H2O
= 36.0 g / 18.02 g/mol
≈ 2.0 mol
Step 3: Calculate the number of moles of carbon.
Since one mole of CO2 contains one mole of carbon atoms, we have 1.5 moles of carbon.
Step 4: Calculate the number of moles of hydrogen.
Since one mole of H2O contains two moles of hydrogen atoms, we have 2.0 moles of hydrogen.
Step 5: Divide the number of moles by the smallest number of moles.
Divide both the number of moles of carbon and hydrogen by 1.5 (the smallest number of moles).
Carbon: 1.5 moles / 1.5 = 1 mole
Hydrogen: 2.0 moles / 1.5 = 1.33 moles
Since we cannot have a fraction in the empirical formula, we need to multiply both values by a number to obtain whole numbers.
Step 6: Multiply the values to obtain whole numbers.
Multiply both the number of moles of carbon and hydrogen by 3 (to get the smallest whole number ratio).
Carbon: 1 mole x 3 = 3
Hydrogen: 1.33 moles x 3 = 4
Step 7: Write the empirical formula.
The empirical formula for the compound is C3H4.