Le Chatelier's Principle: Temperature

Summarize Le Chatelier's principle.

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NGSS.HS-PS1-5

What is the problem asking you to do?

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NGSS.HS-PS1-5

1. 1. Identify the reaction type: A negative ΔH∘ indicates that the forward reaction (the production of ammonia) is exothermic, meaning it releases heat. A positive ΔH∘ is endothermic.

What type of reaction has a ΔH∘ -92 kJ mol ^-1

• Endothermic

• Exothermic

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NGSS.HS-PS1-4

1. 1. Identify the reaction type: A negative ΔH∘ indicates that the forward reaction (the production of ammonia) is exothermic, meaning it releases heat. A positive ΔH∘ is endothermic.

What type of reaction has a ΔH∘ 145 kJ mol ^-1

• Endothermic

• Exothermic

Tags

NGSS.HS-PS1-4

2. 2. Identify the change

3. What change is being manipulated in this problem?

• Temperature

• Pressure

• Concentration

• Color

Tags

NGSS.HS-PS1-5

When the temperature of the system is increased, you're essentially adding more heat. According to Le Châtelier's principle, the system will try to counteract this addition of heat by shifting in the direction that consumes heat.

Since the reverse reaction is endothermic and absorbs heat, the equilibrium will shift to the left, favoring the reactants (N₂​ and H₂​).

QUESTION: What happens when you increase the temperature of a system?

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NGSS.HS-PS1-4

NGSS.HS-PS1-6

When the temperature of the system is increased, you're essentially adding more heat. According to Le Châtelier's principle, the system will try to counteract this addition of heat by shifting in the direction that consumes heat.

Since the reverse reaction is endothermic and absorbs heat, the equilibrium will shift to the left, favoring the reactants (N₂​ and H₂​).

QUESTION: Explain how the system will counteract the addition of heat?

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NGSS.HS-PS3-4

Therefore, an increase in temperature will favor the reverse reaction, shifting the equilibrium to the left and decreasing the yield of ammonia. This is why, in industrial production, a compromise temperature is used: high enough for a good reaction rate, but not so high that it significantly reduces the product yield.

QUESTION: Which way does the reaction shift if the reverse reaction is favored?

• Left

• Right

Therefore, an increase in temperature will favor the reverse reaction, shifting the equilibrium to the left and decreasing the yield of ammonia. This is why, in industrial production, a compromise temperature is used: high enough for a good reaction rate, but not so high that it significantly reduces the product yield.

QUESTION: What happens to the product when the reverse reaction is favored?

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NGSS.HS-PS1-5

NGSS.HS-PS1-6

Therefore, an increase in temperature will favor the reverse reaction, shifting the equilibrium to the left and decreasing the yield of ammonia. This is why, in industrial production, a compromise temperature is used: high enough for a good reaction rate, but not so high that it significantly reduces the product yield.

QUESTION: Why is a compromise temperature used in the Haber process?

Tags

NGSS.HS-PS1-5