Finding equilibrium expression for an equilibrium equation

In summary, the conversation discusses the writing of an equilibrium constant in the d(i) part of a problem. It is noted that solids and liquids are not included in the equation. The questioner asks if there will be an expression for the reaction, to which the responder states that there is always an expression, but materials with certain properties are not included because their activities evaluate to 1. The problem deals with a mixture of liquids rather than a typical solution. The questioner is advised to convert masses into moles and find initial concentrations to complete the problem.
  • #1
haha0p1
46
9
Homework Statement
Write the equilibrium expression for this reaction
Relevant Equations
Kc=(product A)×(product B)
----------------------------------------
(Reactant A)×(Reactant B)
In the d(i) part, we are asked to write an equilibrium constant. It was mentioned in the chapter that solids and liquids will not be added in the equation. So, I think that there is not going to be any Expression for this reaction as all the reactants and products are liquids. Is my answer right?
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  • #2
Solids and immiscible liquids.
 
  • #3
I suggest you use square brackets in your above expressions to remind yourself that you are dealing with molarities.
 
  • #4
You need to convert the masses of your reactants into moles using their respective molar masses. You can then find the initial concentrations from the moles and the given volume. The reactions shows the reactants as liquids but they are being dissolved in a solvent which then makes them aqueous. You need the values for part (a) in order to complete the entire problem.
 
  • #5
There's always an expression. The reason we don't include materials with certain properties is because their activities evaluate to 1, i.e. something multiplied by 1 is itself, so it's not written out. The confusion likely arises from the fact that we usually only include (g) and (aq) samples in these equations, since a lot of problems are concerned with dissolved gases, salts or acid/bases. However, this problem deals with a mixture of liquids rather than what we would usually consider a solution (i.e. something solid or gaseous dissolved).
 

FAQ: Finding equilibrium expression for an equilibrium equation

What is an equilibrium expression in chemistry?

An equilibrium expression is a mathematical equation that describes the ratio of the concentrations of products to reactants at equilibrium for a reversible chemical reaction. It is derived from the balanced chemical equation and is used to predict the direction of the reaction and the concentrations of reactants and products at equilibrium.

How do you write an equilibrium expression for a given reaction?

To write an equilibrium expression, you first need the balanced chemical equation for the reaction. For a general reaction of the form aA + bB ⇌ cC + dD, the equilibrium expression (Keq) is given by: Keq = [C]c[D]d / [A]a[B]b, where [A], [B], [C], and [D] are the molar concentrations of the reactants and products at equilibrium, and a, b, c, and d are their respective coefficients from the balanced equation.

What is the significance of the equilibrium constant (Keq)?

The equilibrium constant (Keq) provides insight into the position of equilibrium for a given reaction. A large Keq (greater than 1) indicates that the equilibrium favors the formation of products, while a small Keq (less than 1) suggests that the equilibrium favors the reactants. When Keq is close to 1, it means that neither the reactants nor the products are significantly favored.

How do changes in concentration, temperature, and pressure affect the equilibrium expression?

Changes in concentration, temperature, and pressure can shift the position of equilibrium according to Le Chatelier's principle, but they do not affect the form of the equilibrium expression itself. However, temperature changes can alter the value of the equilibrium constant (Keq). For exothermic reactions, increasing the temperature decreases Keq, while for endothermic reactions, increasing the temperature increases Keq. Changes in concentration and pressure shift the equilibrium position but do not change the value of Keq.

Can you provide an example of finding an equilibrium expression?

Sure! Consider the reaction: N2 (g) + 3H2 (g) ⇌ 2NH3 (g). The equilibrium expression for this reaction is written as: Keq = [NH3

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