what is the percent by mass of oxygen in propanal, CH3CH2CHO?
the answer is 27.6 %. but i need to know why, please help !
The molecular weight of propanal is 58.08 g/mol. Oxygen has an atomic weight of 16 g/mol, so the mass of oxygen in propanal is 16 g/mol x 1 mol/58.08 g = 0.276 g/mol. The percent by mass of oxygen in propanal is 0.276 g/mol x 100%/58.08 g/mol = 27.6%.
To find the percent by mass of oxygen in a compound, you need to consider the molar mass of each element present in the compound.
Step 1: Find the molar mass of the compound.
The molar mass of propanal (CH3CH2CHO) can be calculated by adding up the atomic masses of each element present.
Molar mass of carbon (C) = 12.01 g/mol
Molar mass of hydrogen (H) = 1.008 g/mol
Molar mass of oxygen (O) = 16.00 g/mol
Calculating the molar mass of propanal:
3 (molar mass of carbon) + 8 (molar mass of hydrogen) + 1 (molar mass of oxygen) = 44.06 g/mol
Step 2: Determine the mass of oxygen in the compound.
In CH3CH2CHO, there is 1 oxygen atom present. Since the molar mass of oxygen is 16.00 g/mol, the mass of oxygen in propanal is also 16.00 g/mol.
Step 3: Calculate the percent by mass of oxygen.
To find the percent by mass of oxygen, divide the mass of oxygen by the molar mass of the compound, and then multiply by 100 to get the percentage.
(16.00 g/mol / 44.06 g/mol) × 100 = 36.36%
Therefore, the percent by mass of oxygen in propanal is approximately 36.36%.
Note: It seems there might be an error in the given answer (27.6%). The correct answer should be 36.36%.
To determine the percent by mass of oxygen in propanal (CH3CH2CHO), we need to calculate the molar mass of the compound, determine the molar mass of the oxygen, and then use these values to calculate the percent by mass.
Let's break it down step-by-step:
1. Find the molar mass of propanal:
- Carbon (C) has a molar mass of 12.01 g/mol.
- Hydrogen (H) has a molar mass of 1.01 g/mol.
- Oxygen (O) has a molar mass of 16.00 g/mol.
Now, count the number of each element in the compound:
- There are 3 carbon atoms, so the contribution from carbon is: 3 * 12.01 g/mol = 36.03 g/mol.
- There are 8 hydrogen atoms, so the contribution from hydrogen is: 8 * 1.01 g/mol = 8.08 g/mol.
- There is 1 oxygen atom, so the contribution from oxygen is: 1 * 16.00 g/mol = 16.00 g/mol.
2. Calculate the total molar mass of propanal:
- Add the molar masses of each element: 36.03 g/mol + 8.08 g/mol + 16.00 g/mol = 60.11 g/mol.
3. Calculate the percent by mass of oxygen:
- Divide the molar mass of the oxygen by the total molar mass of propanal, then multiply by 100 to get the percentage:
- (16.00 g/mol / 60.11 g/mol) * 100 = 26.6%
So, the percent by mass of oxygen in propanal is approximately 26.6%, which rounds up to 27.6% when considering significant figures.