Lecture on Gas Reactions and Stoichiometry
Mixing of Gases and Reaction
- Initial Setup:
- Oxygen: 1.50 liters at 2.50 atm
- Nitrogen Monoxide: 6 liters at 0.798 atm
- Temperature: 31.5°C
- Moles Calculated: 0.150 moles O₂, 0.191 moles NO
- After Mixing (Before Reaction):
- New Partial Pressures: 0.50 atm (O₂), 0.637 atm (NO)
- Total Pressure: 1.137 atm
Chemical Reaction
- Reaction: 2 NO + O₂ → 2 NO₂
- Limiting Reagent Problem:
- Calculate moles of NO₂ formed based on limiting reagent
- Oxygen as Limiting Reagent: 0.300 moles NO₂ could form
- Nitrogen Monoxide as Limiting Reagent: 0.191 moles NO₂ could form
- Limiting Reagent: Nitrogen Monoxide (0.191 moles NO₂ formed)
Calculating After Reaction
- Products and Reactants After Reaction:
- NO: All used up (0 moles left)
- O₂: 0.055 moles left
- NO₂: 0.191 moles formed
- Pressure Calculations using PV=nRT:
- NO₂: 0.637 atm
- NO: 0 atm (all used)
- O₂: 0.18 atm
- Total Pressure After Reaction: 0.82 atm
Alternative Method (Using Partial Pressures)
- Stoichiometry Using Partial Pressures:
- 2 atm NO react with 1 atm O₂
- If O₂ is limiting: 1 atm NO₂ formed
- If NO is limiting: 0.637 atm NO₂ formed
- Calculations:
- NO₂: 0.637 atm (from NO limiting)
- O₂ Remaining: 0.182 atm
Gas Law Stoichiometry with Phases
- Example: Alcohol Fermentation
- Reaction: C₆H₁₂O₆ (solid) → 2 C₂H₅OH (liquid) + 2 CO₂ (gas)
- Percent Yield Calculation:
- Given: 5.97 g glucose, 1.44 liters CO₂ at 293 K, 0.984 atm
- Theoretical yield: Calculate moles of CO₂ from glucose
- Actual yield: Use PV=nRT to find moles CO₂
- Percent Yield: (Actual/Theoretical) x 100% = 88.9%
Conceptual Understanding
- Using PV=nRT:
- Calculate number of moles and pressures
- Apply gas laws to stoichiometry problems
- Consider multi-phase reactions (solid, liquid, gas)
Key Formulas
- Ideal Gas Law: PV = nRT
- Stoichiometry: Use ratios from balanced equations
This lecture covers the principles of gas mixing and reactions, focusing on stoichiometry, limiting reagents, and using the ideal gas law in calculations.