Question
Systems that have gaseous reactants and products behave a little bit differently when an experimenter works to force the system out of equilibrium in order to obtain a product. The mechanism of stress that is used is "pressure". [If you need to review this concept a little bit it can be found in Lesson 7.4 - Changing Reaction Rates. Guided notes might help support you, or even reviewing Unit 6 Rates of Reaction Lesson 2 a little bit. --- I am certain you can work through this!]
Added pressure, or force exerted over area, can increase the number of collisions among particles in a closed system. Hopefully this makes sense. The system works to balance numbers of 'moles' of reactant(s) and product(s) throughout. We can find the number of moles by BALANCING the EQUATION. Here is our example from the Haber-Bosch process we used in Unit 6 portfolio work. It explains 'why' the reaction is more efficient at lower temperatures.
N2(g) + 3H2(g) ⇌ 2NH3 (g) + heat energy
nitrogen gas + hydrogen gas react reversibly to form ammonia gas + heat
Please use the image above to help you count moles of reactants and products to determine which direction the shift will take the experimenter under the conditions applied. The equation is balanced for you.
(6 points)
Forward Reaction (shift right) Reverse Reaction (shift left)
The experimenter counts 2 moles of nitrogen and 6 moles of hydrogen gas in the closed system.
The experimenter ADDS the catalyst of iron to break the triple covalent bonds in nitrogen gas. [Check Lesson 7.4 for help if needed!]
The experimenter REMOVES heat from the closed system.
The experimenter ADDS heat to the closed system.
The experiment counts 8 moles of ammonia in the closed system.
The experimenter counts 1 mole of ammonia in the closed system.
Added pressure, or force exerted over area, can increase the number of collisions among particles in a closed system. Hopefully this makes sense. The system works to balance numbers of 'moles' of reactant(s) and product(s) throughout. We can find the number of moles by BALANCING the EQUATION. Here is our example from the Haber-Bosch process we used in Unit 6 portfolio work. It explains 'why' the reaction is more efficient at lower temperatures.
N2(g) + 3H2(g) ⇌ 2NH3 (g) + heat energy
nitrogen gas + hydrogen gas react reversibly to form ammonia gas + heat
Please use the image above to help you count moles of reactants and products to determine which direction the shift will take the experimenter under the conditions applied. The equation is balanced for you.
(6 points)
Forward Reaction (shift right) Reverse Reaction (shift left)
The experimenter counts 2 moles of nitrogen and 6 moles of hydrogen gas in the closed system.
The experimenter ADDS the catalyst of iron to break the triple covalent bonds in nitrogen gas. [Check Lesson 7.4 for help if needed!]
The experimenter REMOVES heat from the closed system.
The experimenter ADDS heat to the closed system.
The experiment counts 8 moles of ammonia in the closed system.
The experimenter counts 1 mole of ammonia in the closed system.
Answers
GPT-4o mini
To analyze the effects of pressure and other changes on the reaction \(\text{N}_2(g) + 3\text{H}_2(g) \rightleftharpoons 2\text{NH}_3(g) + \text{heat}\), we must count the moles of reactants and products.
**Initial balanced equation:**
- Reactants: 1 mole of \(\text{N}_2\) + 3 moles of \(\text{H}_2\) = **4 total moles of reactants**
- Products: 2 moles of \(\text{NH}_3\) = **2 total moles of products**
The reaction is a case of either increasing or decreasing the pressure in a closed system, which shifts the equilibrium to favor the side with fewer moles of gas.
Here's an examination of each experimental scenario:
1. **The experimenter counts 2 moles of nitrogen and 6 moles of hydrogen gas in the closed system.**
- Moles of reactants: \(2 + 6 = 8\) moles
- Moles of products: \(0\) (none, since no ammonia is produced yet)
- **Shift: Reverse reaction (shift left)** (with 8 moles of reactants, the system will favor products' formation if pressure is increased).
2. **The experimenter ADDS the catalyst of iron to break the triple covalent bonds in nitrogen gas.**
- A catalyst does not change the position of equilibrium; it only increases the rate at which equilibrium is reached.
- **Shift: No shift** (equilibrium position remains unchanged).
3. **The experimenter REMOVES heat from the closed system.**
- This reaction is exothermic (produces heat), thus removing heat will shift the equilibrium to the right, towards the products.
- **Shift: Forward reaction (shift right)**.
4. **The experimenter ADDS heat to the closed system.**
- Adding heat will shift the equilibrium towards the endothermic direction, which in this case is the reverse reaction (to the left, forming reactants).
- **Shift: Reverse reaction (shift left)**.
5. **The experiment counts 8 moles of ammonia in the closed system.**
- Moles of products (ammonia): 8 moles
- Moles of reactants: \(0\) (none, since there are no reactants available).
- **Shift: Reverse reaction (shift left)** (the system will favor the formation of reactants due to excess product).
6. **The experimenter counts 1 mole of ammonia in the closed system.**
- Moles of products: 1
- Moles of reactants: \(2 + 3 = 5\) moles (assuming the completion of the direction based on the stoichiometry).
- **Shift: Forward reaction (shift right)** (the system will favor the formation of more ammonia under increased pressure).
### Summary of shifts:
1. No shift
2. Forward reaction (shift right)
3. Reverse reaction (shift left)
4. Reverse reaction (shift left)
5. Reverse reaction (shift left)
6. Forward reaction (shift right)
**Initial balanced equation:**
- Reactants: 1 mole of \(\text{N}_2\) + 3 moles of \(\text{H}_2\) = **4 total moles of reactants**
- Products: 2 moles of \(\text{NH}_3\) = **2 total moles of products**
The reaction is a case of either increasing or decreasing the pressure in a closed system, which shifts the equilibrium to favor the side with fewer moles of gas.
Here's an examination of each experimental scenario:
1. **The experimenter counts 2 moles of nitrogen and 6 moles of hydrogen gas in the closed system.**
- Moles of reactants: \(2 + 6 = 8\) moles
- Moles of products: \(0\) (none, since no ammonia is produced yet)
- **Shift: Reverse reaction (shift left)** (with 8 moles of reactants, the system will favor products' formation if pressure is increased).
2. **The experimenter ADDS the catalyst of iron to break the triple covalent bonds in nitrogen gas.**
- A catalyst does not change the position of equilibrium; it only increases the rate at which equilibrium is reached.
- **Shift: No shift** (equilibrium position remains unchanged).
3. **The experimenter REMOVES heat from the closed system.**
- This reaction is exothermic (produces heat), thus removing heat will shift the equilibrium to the right, towards the products.
- **Shift: Forward reaction (shift right)**.
4. **The experimenter ADDS heat to the closed system.**
- Adding heat will shift the equilibrium towards the endothermic direction, which in this case is the reverse reaction (to the left, forming reactants).
- **Shift: Reverse reaction (shift left)**.
5. **The experiment counts 8 moles of ammonia in the closed system.**
- Moles of products (ammonia): 8 moles
- Moles of reactants: \(0\) (none, since there are no reactants available).
- **Shift: Reverse reaction (shift left)** (the system will favor the formation of reactants due to excess product).
6. **The experimenter counts 1 mole of ammonia in the closed system.**
- Moles of products: 1
- Moles of reactants: \(2 + 3 = 5\) moles (assuming the completion of the direction based on the stoichiometry).
- **Shift: Forward reaction (shift right)** (the system will favor the formation of more ammonia under increased pressure).
### Summary of shifts:
1. No shift
2. Forward reaction (shift right)
3. Reverse reaction (shift left)
4. Reverse reaction (shift left)
5. Reverse reaction (shift left)
6. Forward reaction (shift right)