AP Chemistry Questions on Gas Stoichiometry: Test Your Knowledge

🧪 Quick Study Guide

• ⚖️ Ideal Gas Law: Relates pressure (P), volume (V), number of moles (n), ideal gas constant (R), and temperature (T): $PV = nRT$. Remember R = 0.0821 L atm / (mol K) or 8.314 J / (mol K).
• 🌡️ Standard Temperature and Pressure (STP): 0°C (273.15 K) and 1 atm. At STP, one mole of any ideal gas occupies 22.4 L.
• ⚗️ Molar Mass: The mass of one mole of a substance, usually expressed in grams per mole (g/mol).
• ⚛️ Stoichiometry: The relationship between the relative quantities of substances taking part in a reaction or forming a compound, typically a ratio of whole integers.
• 🧮 Gas Stoichiometry Steps:
  1. 📝 Balance the chemical equation.
  2. 🔢 Convert given quantities to moles.
  3. 🎯 Use the mole ratio from the balanced equation to find moles of the desired gas.
  4. 📐 Convert moles of the desired gas to the required units (e.g., volume using the Ideal Gas Law).

Practice Quiz

1. What volume of oxygen gas (O₂) is required to completely combust 10.0 L of methane gas (CH₄) at STP, according to the following balanced equation? CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(g)
1. 5.0 L
2. 10.0 L
3. 20.0 L
4. 30.0 L
2. If 5.0 g of nitrogen gas (N₂) reacts with excess hydrogen gas (H₂) according to the reaction N₂(g) + 3H₂(g) → 2NH₃(g), what volume of ammonia (NH₃) is produced at STP?
1. 3.99 L
2. 7.98 L
3. 11.2 L
4. 22.4 L
3. What mass of potassium chlorate (KClO₃) is needed to produce 5.6 L of oxygen gas (O₂) at STP, according to the following balanced equation? 2KClO₃(s) → 2KCl(s) + 3O₂(g)
1. 10.2 g
2. 12.7 g
3. 15.3 g
4. 20.4 g
4. At constant temperature and pressure, if 2 moles of CO₂ have a volume of 44.8 L, what would be the volume of 0.5 moles of O₂ under the same conditions?
1. 5.6 L
2. 11.2 L
3. 22.4 L
4. 89.6 L
5. A rigid container holds 10.0 g of hydrogen gas (H₂) at 25°C. If 5.0 g of helium gas (He) is added to the container, what happens to the pressure? (Assume constant volume and temperature)
1. Pressure decreases
2. Pressure increases
3. Pressure remains the same
4. Impossible to determine
6. Ammonium nitrate (NH₄NO₃) decomposes upon heating to produce nitrogen gas (N₂), oxygen gas (O₂), and water vapor. If 40.0 g of ammonium nitrate is decomposed, what volume of nitrogen gas is produced at STP? 2NH₄NO₃(s) → 2N₂(g) + O₂(g) + 4H₂O(g)
1. 11.2 L
2. 16.8 L
3. 22.4 L
4. 44.8 L
7. If 10.0 L of hydrogen gas and 5.0 L of oxygen gas react according to the reaction 2H₂(g) + O₂(g) → 2H₂O(g), what volume of water vapor is produced, assuming all gases are measured at the same temperature and pressure?
1. 5.0 L
2. 10.0 L
3. 15.0 L
4. 20.0 L