3H2(g) + N2(g) reverse reaction arrow 2NH3(g)
What factors would affect the equilibrium constant for the reaction above? (Select all that apply.)
increasing the H2 concentration decreasing the NH3 concentration increasing the temperature
decreasing the temperature
increasing the pressure
decreasing the pressure
adding a catalyst
**I thought the answer was the first six (all except the catalyst, but I got it wrong...)
The equilibrium constant (K) expresses the ratio of product concentrations to reactant concentrations at equilibrium for a chemical reaction. It is determined by the stoichiometry of the balanced equation and the temperature. In this case, the balanced equation is:
3H2(g) + N2(g) ⇌ 2NH3(g)
Factors that can affect the equilibrium constant include:
1. Temperature: Changing the temperature can affect the equilibrium constant. In general, increasing the temperature favors the endothermic reaction, while decreasing the temperature favors the exothermic reaction. So, increasing the temperature would affect the equilibrium constant in this reaction.
2. Concentration: Changing the concentration of the reactants or products can affect the equilibrium constant. According to Le Chatelier's principle, if you increase the concentration of a reactant, it will shift the reaction towards the products to counteract the change. In this case, increasing the concentration of H2 or decreasing the concentration of NH3 will affect the equilibrium constant.
3. Pressure: Changing the pressure can affect the equilibrium constant, but only if the reaction involves gases. In this reaction, all species are in gas phase, so changing the pressure will affect the equilibrium. According to Le Chatelier's principle, if you increase the pressure, it will shift the reaction towards the side with fewer moles of gas, and if you decrease the pressure, it will shift towards the side with more moles of gas.
Based on these factors, the correct options are:
- Increasing the H2 concentration
- Decreasing the NH3 concentration
- Increasing the temperature
- Decreasing the temperature
- Increasing the pressure
- Decreasing the pressure
For the given reaction 3H2(g) + N2(g) ⇋ 2NH3(g), the factors that would affect the equilibrium constant include:
1. Increasing the H2 concentration: According to Le Chatelier's principle, if the concentration of a reactant (in this case, H2) is increased, the equilibrium will shift toward the products to reduce the excess concentration. Therefore, the equilibrium constant (K) would be affected.
2. Decreasing the NH3 concentration: Similar to the previous point, if the concentration of a product (in this case, NH3) is decreased, the equilibrium will shift in the forward direction to produce more products and compensate for the decrease. Hence, the equilibrium constant would be influenced.
3. Increasing the temperature: In an exothermic reaction like the one given, increasing the temperature will shift the equilibrium in the reverse reaction (to the left) to consume the excess heat. As a result, the equilibrium constant will likely decrease.
4. Decreasing the temperature: Conversely, lowering the temperature of an exothermic reaction will favor the forward reaction (to the right), producing more products. This will lead to an increase in the equilibrium constant.
5. Increasing the pressure: In this reaction, the total number of moles of gas decreases when H2 and N2 react to form NH3. According to Le Chatelier's principle, an increase in pressure will push the equilibrium towards the side with fewer moles of gas (the right in this case). Thus, the equilibrium constant will be affected.
6. Decreasing the pressure: The opposite effect can be expected if the pressure is reduced. The equilibrium will shift in the direction to create more moles of gas (the left side of the reaction) to compensate for the decrease in pressure. Therefore, the equilibrium constant will likely change.
7. Adding a catalyst: Lastly, adding a catalyst does not affect the equilibrium constant but rather speeds up the attainment of equilibrium by lowering the activation energy. Hence, the equilibrium constant remains unaffected.
So, the correct answers are:
- Increasing the H2 concentration
- Decreasing the NH3 concentration
- Increasing the temperature
- Decreasing the temperature
- Increasing the pressure
- Decreasing the pressure