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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 ADDS heat to the closed system. The experimenter counts 2 moles of nitrogen and 6 moles of hydrogen gas in 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. 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. Skip to navigation

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To analyze the effects of pressure and changes in conditions on the given reaction, we can use Le Chatelier's Principle. According to this principle, if a system at equilibrium is subjected to a change in pressure, temperature, concentration, or volume, the system will shift in a direction that counteracts the effect of the change.

Let’s examine the reaction step by step with respect to the conditions you've provided:

Reaction Equation

\[ \text{N}_2(g) + 3\text{H}_2(g) \rightleftharpoons 2\text{NH}_3(g) + \text{heat} \]

Molar Analysis

  1. Moles of Reactants:

    • Nitrogen (\( N_2 \)): 1 mole
    • Hydrogen (\( H_2 \)): 3 moles
    • Total Reactants: 1 + 3 = 4 moles

  2. Moles of Products:

    • Ammonia (\( NH_3 \)): 2 moles
    • Total Products: 2 moles

Analysis of Each Experimenter's Action

  1. Adding Heat:

    • When heat is added to the system, the equilibrium will shift to the right (forward reaction) to consume the excess heat, favoring the production of more products (ammonia).

  2. Counting Moles:

    • With 2 moles of nitrogen and 6 moles of hydrogen, along with 8 moles of ammonia, the reaction conditions favor products (since there are significantly more ammonia moles than reactants). However, remember that excess moles of \( NH_3 \) can still affect reactant-product balance.

    • If you counted 1 mole of ammonia, this indicates a higher proportion of reactants than products, which would favor the reverse reaction (shift to the left) under this condition.

  3. Adding a Catalyst (Iron):

    • Adding a catalyst does not shift the equilibrium. It only speeds up the rate at which equilibrium is reached for both forward and reverse reactions. So, the effect of adding iron has no impact on the direction of the shift.

  4. Removing Heat:

    • When heat is removed from the system, the equilibrium will shift to the right (forward reaction) to produce more heat, thus favoring the formation of ammonia.

Summary of Shifts

  • Adding Heat: Shift right (forward reaction)
  • Counting 8 moles of ammonia: Indicates favoring products; however, needs to be analyzed alongside reactant amounts
  • Counting 1 mole of ammonia: Shift left (reverse reaction); not enough product to balance reactants
  • Adding Catalyst: No shift (accelerates both directions)
  • Removing Heat: Shift right (forward reaction)

In conclusion, under the conditions of adding heat and subsequently removing heat, the system will adjust its position accordingly to favor the production of ammonia, while the presence of both nitroge and hydrogen moles will dictate shifts based on their relative numbers and concentrations.