Sure! Let's analyze the problem step-by-step and apply Le Chatelier's Principle to determine how to decrease the yield of carbon dioxide (CO₂) in the combustion of propane (C₃H₈).
Given the reaction:
[tex]\[ C_3H_{8(g)} + 5O_{2(g)} \rightarrow 3CO_{2(g)} + 4H_{2O(g)} \][/tex]
with ΔH = -2219.1 kJ/mol, it means the reaction is exothermic (since ΔH < 0).
To decrease the yield of CO₂, we want to shift the equilibrium of the reaction to the left (towards the reactants). According to Le Chatelier's Principle, we can do this by making specific changes to the reaction conditions.
### Step 1: Changing Concentration
By increasing the concentration of CO₂ in the reaction mixture, the equilibrium will be shifted to counteract this change, i.e., towards the reactants. Thus, increasing the concentration of CO₂ will decrease its yield.
### Step 2: Changing Temperature
For an exothermic reaction, increasing the temperature will shift the equilibrium towards the reactants, as the system will try to absorb the extra heat by favoring the endothermic direction (left side). As a result, increasing the temperature will decrease the yield of CO₂.
### Step 3: Changing Pressure
Pressure changes affect the equilibrium position depending on the number of moles of gas on each side of the reaction. In our reaction:
- Reactants: [tex]\( 1 \text{ mol C}_3H_8 + 5 \text{ mol O}_2 = 6 \text{ moles} \)[/tex]
- Products: [tex]\( 3 \text{ mol CO}_2 + 4 \text{ mol H}_2O = 7 \text{ moles} \)[/tex]
Since there are more moles of gas on the product side (7 moles) compared to the reactant side (6 moles), increasing the pressure will favor the side with fewer moles of gas (the reactants). Therefore, increasing the pressure will shift the equilibrium to the left and decrease the yield of CO₂.
### Conclusion
To decrease the yield of CO₂ in the combustion of propane, we can:
1. Increase the concentration of CO₂ - This shifts the equilibrium to the left.
2. Increase the temperature - For an exothermic reaction, this shifts the equilibrium towards the reactants.
3. Increase the pressure - This shifts the equilibrium towards the side with fewer moles of gas (the reactants).
By making these adjustments, we can decrease the yield of CO₂ in the given reaction.
