The foul odor of rancid butter is due largely to butyric acid, a compound containing carbon, hydrogen, and oxygen. Combustion analysis of a 4.30-g sample of butyric acid produced 8.59g CO_2 and 3.52 g H_2O.Find the empirical formula for butyric acid.
I would convert g CO2 and g H2O to percent C and percent H, then subtract the sum of C and H from 100% to obtain percent O. Take a 100 grams sample (which gives grams = percent), finally convert to moles C, H, O, and find the ratio to each of the elements in small whole numbers.
Post your work if you get stuck.
C2H4O
шТну
To find the empirical formula for butyric acid, we need to determine the ratio of the atoms present in the compound. We can do this by finding the moles of carbon, hydrogen, and oxygen using the given data.
Step 1: Convert the given masses of CO₂ and H₂O to moles.
- Moles of CO₂ = mass of CO₂ / molar mass of CO₂
- Moles of H₂O = mass of H₂O / molar mass of H₂O
The molar mass of CO₂ (carbon dioxide) is 44.01 g/mol, and the molar mass of H₂O (water) is 18.02 g/mol.
Moles of CO₂ = 8.59 g / 44.01 g/mol
Moles of H₂O = 3.52 g / 18.02 g/mol
Step 2: Determine the moles of carbon, hydrogen, and oxygen in butyric acid.
- Carbon: Each molecule of CO₂ contains 1 carbon atom. So, the moles of carbon will be the same as the moles of CO₂.
- Hydrogen: Each molecule of H₂O contains 2 hydrogen atoms. So, to get the moles of hydrogen, we need to multiply the moles of H₂O by 2.
- Oxygen: To determine the moles of oxygen, we subtract the moles of carbon and hydrogen from the total number of moles.
Moles of carbon = Moles of CO₂
Moles of hydrogen = (Moles of H₂O) x 2
Moles of oxygen = Total moles - (Moles of carbon + Moles of hydrogen)
Step 3: Calculate the molar ratios of carbon, hydrogen, and oxygen.
To find the empirical formula, we simplify the mole ratios by dividing by the smallest number of moles.
Divide the moles of carbon, hydrogen, and oxygen by the smallest number of moles among them. Then round off the ratios to the nearest whole number to determine the subscripts in the empirical formula.
Finally, we can write the empirical formula for butyric acid using the determined subscripts.
Now, let's calculate the empirical formula for butyric acid.
Given data:
Mass of CO₂ = 8.59 g
Mass of H₂O = 3.52 g
Calculations:
Moles of CO₂ = 8.59 g / 44.01 g/mol = 0.1957 mol
Moles of H₂O = 3.52 g / 18.02 g/mol = 0.1953 mol
Moles of carbon = 0.1957 mol
Moles of hydrogen = 0.1953 mol x 2 = 0.3906 mol
Moles of oxygen = (0.1957 mol + 0.3906 mol) - (0.1957 mol + 0.3906 mol) = 0.1957 mol
Molar ratios:
Carbon : Hydrogen : Oxygen = 0.1957 mol : 0.3906 mol : 0.1957 mol
Dividing by the smallest number of moles (0.1957 mol) gives us:
Carbon : Hydrogen : Oxygen = 1 : 2 : 1
The empirical formula for butyric acid is CH₂O.