How Do You Determine the Equilibrium Constant for Modified Reactions?

In summary, the conversation discusses the equilibrium constant Keq for two different reactions involving gases. The value of Keq for the first reaction is given, and the question is to find the value for the second reaction, which is half of the first. The answer is found to be 1/K for the first reaction and 1/K^2 for the second reaction. The conversation also addresses the difficulty in finding the right arrow symbol to denote equilibrium in the equations.
  • #1
shaa
6
0
Hello, I'm new to the forums and did in fact search for my thread before posting. I couldn't find anything that helped me with what I'm looking for. With that said, the problem I'm having is:

1) The value of Keq for the equilibrium H2+I2 → 2 HI is 794 at 25°C. What is the value of Keq for the equilibrium below?
1/2 H2+1/2 I2 → HI

2) The equilibrium constant for reaction 1 is K. The equilibrium constant for reaction 2 is _____.
1: SO2+1/2 O2 → SO3
2: 2SO3 → 2SO2+O2

I apologize for not denoting an equation at equilibrium, but I couldn't find the right arrow in the "Quick Symbols" box. Both equations are at equilibrium and involve only matter in the gaseous state.
 
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  • #2
I've gotten the first question, considering that the second reaction is half of the first. Resulting in: x1/2, and x being the original Kc.

I know what the answer to the first question is, but I'm having difficulty understanding why it is what it is.
 
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  • #3
This is a simple math. Write reaction quotient for each reaction.
 
  • #4
It states that the equilibrium constant for reaction 1 is = k. The equilibrium constant for reaction 2 is = 1/k2.

The answer makes complete sense given a general form of an equilibrium reaction, but why wouldn't the first reaction be = 1/k or the second be = -1/k2?
 
  • #5
I don't understand why you think it should be. If you write reaction quotients for each reaction and compare them, it is obvious what value the new equilibrium constant has.

You can as well ask why [itex]\sqrt 2[/itex] doesn't equal [itex]\pi[/itex].
 
  • #6
Hahahah. Of course. It's the inverse reaction and it double. Thus 1/k2.
Thanks? :P
 
  • #7
shaa said:
I apologize for not denoting an equation at equilibrium, but I couldn't find the right arrow in the "Quick Symbols" box. Both equations are at equilibrium and involve only matter in the gaseous state.
One of these might help; feel free to copy-and-paste for future use, or bookmark the links in my sig:
← or ↔

p.s. Welcome to Physics Forums.
 
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Related to How Do You Determine the Equilibrium Constant for Modified Reactions?

1. What is an equilibrium constant?

An equilibrium constant is a numerical value that represents the equilibrium state of a chemical reaction. It is a measure of the relative amount of products and reactants at equilibrium, and it is used to calculate the direction and extent of a reaction.

2. How is an equilibrium constant calculated?

The equilibrium constant is calculated by taking the concentrations (or partial pressures) of the products and dividing them by the concentrations (or partial pressures) of the reactants, each raised to their respective stoichiometric coefficients. This can be represented by the equation Keq = [Products]/[Reactants].

3. What factors can affect an equilibrium constant?

An equilibrium constant can be affected by changes in temperature, pressure, and concentration of reactants and products. Changes in these factors can shift the equilibrium position, altering the value of the equilibrium constant.

4. How can an equilibrium constant be used to predict the direction of a reaction?

If the value of the equilibrium constant is greater than 1, it indicates that the products are favored at equilibrium and the reaction will proceed towards the products. If the value is less than 1, it means the reactants are favored and the reaction will proceed towards the reactants. If the value is equal to 1, it indicates that the reactants and products are present in equal amounts at equilibrium.

5. Can the equilibrium constant be changed?

The value of the equilibrium constant is a characteristic of a specific chemical reaction at a specific temperature. It cannot be changed, but it can be influenced by changing the conditions of the reaction, such as temperature, pressure, and concentrations of reactants and products.

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