What effect do the listed changes have on the position of the equilibrium in the reaction of carbon with hydrogen?
C(s) + 2 H₂(g) ⇌ CH₄(g) ∆H = -18 kcal/mol (-75kJ/mol)
a. Increasing temperature

Verified step by step guidance

1. Identify the type of reaction: The reaction is exothermic because the enthalpy change (∆H) is negative (-18 kcal/mol or -75 kJ/mol). This means heat is released as a product of the reaction.
2. Apply Le Châtelier's Principle: This principle states that if a system at equilibrium is disturbed, the system will adjust to counteract the disturbance and restore equilibrium.
3. Analyze the effect of increasing temperature: In an exothermic reaction, heat is considered a product. Increasing the temperature adds heat to the system, which shifts the equilibrium position to favor the reactants (C(s) and H2(g)) to reduce the added heat.
4. Conclude the shift in equilibrium: The equilibrium will shift to the left (toward the reactants) as a response to the increase in temperature.
5. Summarize the reasoning: By increasing the temperature, the system counteracts the disturbance by favoring the endothermic direction (reactant formation) to absorb the excess heat, thereby shifting the equilibrium to the left.

Key Concepts

Le Chatelier's Principle

Le Chatelier's Principle states that if a dynamic equilibrium is disturbed by changing the conditions, the position of equilibrium shifts to counteract the change. In the context of the given reaction, increasing the temperature will shift the equilibrium position in the direction that absorbs heat, which is the endothermic direction.

Endothermic and Exothermic Reactions

Reactions can be classified as endothermic or exothermic based on their heat exchange with the surroundings. The reaction of carbon with hydrogen to form methane (CH4) is exothermic, as indicated by the negative enthalpy change (∆H = -18 kcal/mol). Increasing temperature affects the equilibrium by favoring the endothermic process, which in this case is the reverse reaction.

Equilibrium Constant (K)

The equilibrium constant (K) quantifies the ratio of the concentrations of products to reactants at equilibrium for a given reaction at a specific temperature. Changes in temperature can alter the value of K, thereby affecting the position of equilibrium. For the reaction in question, increasing temperature will decrease K, favoring the reactants over the products.