Calculate the percentage by mass of oxygen in the following compounds: (c) acetaminophen, C₈H₉NO₂ (d) cyclopropanone, C₃H₄O

Verified step by step guidance

1. Step 1: Calculate the molar mass of acetaminophen. The molar mass of a compound is calculated by adding up the molar masses of each of its constituent elements. The molar mass of carbon (C) is approximately 12.01 g/mol, hydrogen (H) is approximately 1.01 g/mol, nitrogen (N) is approximately 14.01 g/mol, and oxygen (O) is approximately 16.00 g/mol. Acetaminophen has 8 carbon atoms, 9 hydrogen atoms, 1 nitrogen atom, and 2 oxygen atoms.
2. Step 2: Calculate the total molar mass of the oxygen in the compound. Since there are 2 oxygen atoms in acetaminophen, you would multiply the molar mass of oxygen by 2.
3. Step 3: Divide the total molar mass of the oxygen by the molar mass of the entire compound. This will give you the fraction of the compound's mass that is due to oxygen.
4. Step 4: Multiply the fraction from step 3 by 100 to convert it to a percentage. This is the percentage by mass of oxygen in acetaminophen.
5. Step 5: Remember to check your work. The percentage by mass of any element in a compound should be a number between 0 and 100. If you get a number outside this range, you've made a mistake somewhere and should go back and check your calculations.

Key Concepts

Molar Mass Calculation

Molar mass is the mass of one mole of a substance, typically expressed in grams per mole (g/mol). To calculate the molar mass of a compound, sum the molar masses of all the atoms in its chemical formula. For acetaminophen (C8H9NO2), this involves calculating the contributions from carbon, hydrogen, nitrogen, and oxygen atoms based on their respective atomic weights.

Percentage by Mass

Percentage by mass is a way to express the concentration of a particular element in a compound. It is calculated by dividing the mass of the element in one mole of the compound by the total molar mass of the compound, then multiplying by 100. This provides a clear understanding of how much of the compound's mass is due to a specific element, such as oxygen in acetaminophen.

Chemical Composition

Chemical composition refers to the types and quantities of atoms that make up a compound. Understanding the chemical formula of a compound, like C8H9NO2 for acetaminophen, allows one to identify the number of each type of atom present. This is essential for calculating both the molar mass and the percentage by mass of individual elements within the compound.