AP Chemistry Questions on Dalton's Law of Partial Pressures

📚 Quick Study Guide

• ⚛️ Dalton's Law states that the total pressure exerted by a mixture of non-reacting gases is equal to the sum of the partial pressures of the individual gases.
• 🔢 The formula is: $P_{total} = P_1 + P_2 + P_3 + ... + P_n$, where $P_{total}$ is the total pressure and $P_1, P_2, P_3, ..., P_n$ are the partial pressures of the individual gases.
• 🌡️ The partial pressure of a gas is the pressure that the gas would exert if it occupied the same volume alone.
• 💡 The partial pressure of a gas can be calculated using the Ideal Gas Law: $P_i = \frac{n_iRT}{V}$, where $P_i$ is the partial pressure of gas i, $n_i$ is the number of moles of gas i, $R$ is the ideal gas constant, $T$ is the temperature, and $V$ is the volume.
• 🧪 Mole fraction ($X_i$) is defined as the ratio of the number of moles of a particular component to the total number of moles of all components in the mixture: $X_i = \frac{n_i}{n_{total}}$. The partial pressure of a gas is also equal to its mole fraction multiplied by the total pressure: $P_i = X_i * P_{total}$.
• 📝 Remember to always use consistent units for pressure, volume, and temperature when applying Dalton's Law or the Ideal Gas Law.

Practice Quiz

1. What does Dalton's Law of Partial Pressures state?
   1. The total pressure of a gas mixture is the product of the partial pressures.
   2. The total pressure of a gas mixture is the sum of the partial pressures.
   3. The partial pressure of a gas is inversely proportional to its mole fraction.
   4. The partial pressure of a gas is equal to the total pressure.
2. A container holds 2 moles of nitrogen gas and 3 moles of oxygen gas. If the total pressure is 10 atm, what is the partial pressure of nitrogen?
   1. 4 atm
   2. 5 atm
   3. 6 atm
   4. 10 atm
3. Which formula correctly represents Dalton's Law of Partial Pressures?
   1. $P_{total} = P_1 * P_2 * P_3$
   2. $P_{total} = P_1 + P_2 + P_3$
   3. $P_{total} = \frac{P_1 + P_2 + P_3}{3}$
   4. $P_{total} = \sqrt{P_1^2 + P_2^2 + P_3^2}$
4. A flask contains 1 mole of helium, 2 moles of neon, and 3 moles of argon. If the total pressure is 12 atm, what is the partial pressure of neon?
   1. 2 atm
   2. 4 atm
   3. 6 atm
   4. 12 atm
5. What is the mole fraction of oxygen in a mixture containing 4 grams of oxygen and 28 grams of nitrogen?
   1. 0.125
   2. 0.25
   3. 0.5
   4. 0.75
6. A container has equal masses of hydrogen and helium. If the total pressure is 3 atm, what is the partial pressure of hydrogen? (Molar mass of H2 = 2 g/mol, He = 4 g/mol)
   1. 1 atm
   2. 1.5 atm
   3. 2 atm
   4. 2.5 atm
7. A mixture of gases contains 0.5 moles of gas A, 1.5 moles of gas B, and 2 moles of gas C. The total pressure is 8 atm. What is the partial pressure of gas B?
   1. 1 atm
   2. 2 atm
   3. 3 atm
   4. 4 atm