Percent Composition Calculation Examples: Step-by-Step

📚 Quick Study Guide

• ⚛️ Percent composition is the percentage by mass of each element in a compound.
• ➗ To calculate it, use the formula: $\frac{\text{mass of element in 1 mole of compound}}{\text{molar mass of compound}} \times 100$
• ⚖️ Molar mass is found by adding up the atomic masses of each element in the compound from the periodic table.
• 🧪 Empirical formulas are the simplest whole number ratio of atoms in a compound, while molecular formulas show the actual number of atoms.
• 💡 Remember to always include units (grams, g/mol) in your calculations!

🧪 Practice Quiz

1. Question 1: What is the percent composition of carbon in methane ($CH_4$)?
   1. A) 25%
   2. B) 75%
   3. C) 80%
   4. D) 20%
2. Question 2: What is the percent composition of oxygen in water ($H_2O$)?
   1. A) 11.1%
   2. B) 88.9%
   3. C) 50%
   4. D) 66.7%
3. Question 3: What is the percent composition of sodium in sodium chloride ($NaCl$)?
   1. A) 60.7%
   2. B) 39.3%
   3. C) 50%
   4. D) 23%
4. Question 4: What is the percent composition of hydrogen in glucose ($C_6H_{12}O_6$)?
   1. A) 40%
   2. B) 6.7%
   3. C) 53.3%
   4. D) 50%
5. Question 5: What is the percent composition of copper in copper(II) sulfate ($CuSO_4$)?
   1. A) 25.4%
   2. B) 39.8%
   3. C) 60.2%
   4. D) 12.7%
6. Question 6: A compound is found to contain 40.0% carbon, 6.7% hydrogen, and 53.3% oxygen. What is its empirical formula?
   1. A) $CHO$
   2. B) $CH_2O$
   3. C) $C_2H_2O$
   4. D) $C_2HO$
7. Question 7: What is the percent composition of nitrogen in ammonium nitrate ($NH_4NO_3$)?
   1. A) 17.5%
   2. B) 35%
   3. C) 52.5%
   4. D) 60%