AP Chemistry Questions on the Mole and Avogadro's Number

📚 Quick Study Guide

• ⚛️ The mole is the SI unit for the amount of a substance. One mole contains exactly $6.02214076 \times 10^{23}$ elementary entities.
• 🔢 Avogadro's Number ($N_A$): $N_A = 6.022 \times 10^{23} \text{ mol}^{-1}$. This number represents the number of entities (atoms, molecules, ions, etc.) in one mole of a substance.
• ⚖️ Molar Mass: The mass of one mole of a substance, expressed in grams per mole (g/mol). It is numerically equal to the atomic or molecular weight of the substance in atomic mass units (amu).
• ➗ Formula for calculating moles: $\text{moles} = \frac{\text{mass}}{\text{molar mass}}$
• ➕ Calculations involving compounds: Determine the molar mass of the compound by adding the atomic masses of all atoms in the chemical formula.
• 🧪 Empirical Formula vs. Molecular Formula: Empirical formula is the simplest whole-number ratio of atoms in a compound, while the molecular formula is the actual number of atoms of each element in a molecule.

🧪 Practice Quiz

1. Question 1: How many moles are present in 12.044 x 10²³ atoms of Carbon?
   1. A) 0.5 moles
   2. B) 1 mole
   3. C) 2 moles
   4. D) 3 moles
2. Question 2: What is the mass of 1 mole of $H_2O$?
   1. A) 16 g
   2. B) 17 g
   3. C) 18 g
   4. D) 19 g
3. Question 3: How many grams of NaCl are needed to make 1 mole of NaCl?
   1. A) 23 g
   2. B) 35.5 g
   3. C) 58.5 g
   4. D) 117 g
4. Question 4: How many molecules are there in 44 grams of $CO_2$?
   1. A) $6.022 \times 10^{23}$
   2. B) $3.011 \times 10^{23}$
   3. C) $12.044 \times 10^{23}$
   4. D) $6.022 \times 10^{22}$
5. Question 5: What is the number of moles in 8 grams of $O_2$?
   1. A) 0.25 moles
   2. B) 0.5 moles
   3. C) 1 mole
   4. D) 2 moles
6. Question 6: How many atoms are there in 0.5 moles of Hydrogen ($H_2$) gas?
   1. A) $6.022 \times 10^{23}$
   2. B) $3.011 \times 10^{23}$
   3. C) $1.2044 \times 10^{24}$
   4. D) $1.5055 \times 10^{23}$
7. Question 7: What volume does 1 mole of any gas occupy at Standard Temperature and Pressure (STP)?
   1. A) 11.2 L
   2. B) 22.4 L
   3. C) 33.6 L
   4. D) 44.8 L