Equilibrium Constant and Reaction Quotient - AP Chemistry
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Which of the following can always be determined based on the equation itself?
Which of the following can always be determined based on the equation itself?
According to the law of mass action, the equilibrium constant expression can always be written given the equation of the reaction itself. The equilibrium-constant expression will be written as the products over the reactants, each raised to their respectively stoichiometric coefficient. The rate law and concentrations can only be determined if there is additional data given.
According to the law of mass action, the equilibrium constant expression can always be written given the equation of the reaction itself. The equilibrium-constant expression will be written as the products over the reactants, each raised to their respectively stoichiometric coefficient. The rate law and concentrations can only be determined if there is additional data given.
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If delta G for a certain reaction is found to be -4955 J/mol, what is the equilibrium constant (Keq) for this reaction?
If delta G for a certain reaction is found to be -4955 J/mol, what is the equilibrium constant (Keq) for this reaction?
Given the equation delta G = -RTln(Keq), plugging in the correct values for the variables will lead us to the correct answer. Using e = 2.7, R = 8.314 J/molK, T= 298 K, and G = -4955 J, we can calculate that K = 7.4.
Given the equation delta G = -RTln(Keq), plugging in the correct values for the variables will lead us to the correct answer. Using e = 2.7, R = 8.314 J/molK, T= 298 K, and G = -4955 J, we can calculate that K = 7.4.
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If cesium metal spontaneously combusts when it comes in contact with room temperature water, which of the following must be true of the equilibrium constant of the reaction at 298 K?
If cesium metal spontaneously combusts when it comes in contact with room temperature water, which of the following must be true of the equilibrium constant of the reaction at 298 K?
When K is greater than 1, the products are favored and the reaction proceeds forward spontaneously. This must be true of the reaction, since it spontaneously occurs when the metal comes into contact with the water.
When K is greater than 1, the products are favored and the reaction proceeds forward spontaneously. This must be true of the reaction, since it spontaneously occurs when the metal comes into contact with the water.
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Consider the following (arbitrary) reaction:
At equilibrium, ![[A_2O_4]=0.25\hspace{1 mm}M](https://vt-vtwa-assets.varsitytutors.com/vt-vtwa/uploads/formula_image/image/20263/gif.latex)
and ![[AO_2]=0.04\hspace{1 mm}M](https://vt-vtwa-assets.varsitytutors.com/vt-vtwa/uploads/formula_image/image/20264/gif.latex)
.
What is the value for the equilibrium constant, 
?
Consider the following (arbitrary) reaction:
At equilibrium,
What is the value for the equilibrium constant,
First, consider the formula for the equilibrium constant of arbitrary reaction:
![K_{eq}=\frac{[C]^c[D]^d}{[A]^a[B]^b}](https://vt-vtwa-assets.varsitytutors.com/vt-vtwa/uploads/formula_image/image/20267/gif.latex)
The formula for the equilibrium constant for this reaction is:
![K_{eq}=\frac{[AO_2]^2}{[A_2O_4]}=\frac{[0.04]^2}{[0.25]}=6.4\times10^{-3}](https://vt-vtwa-assets.varsitytutors.com/vt-vtwa/uploads/formula_image/image/20268/gif.latex)
First, consider the formula for the equilibrium constant of arbitrary reaction:
The formula for the equilibrium constant for this reaction is:
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Why do the concentrations of pure liquids and solids not appear in the equilibrium constant expression?
Why do the concentrations of pure liquids and solids not appear in the equilibrium constant expression?
This is one of the properties of the law of mass action—the concentrations of pure solids and liquids don't change over the course of the reaction.
This is one of the properties of the law of mass action—the concentrations of pure solids and liquids don't change over the course of the reaction.
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Which of the following is not a property of the law of mass action?
Which of the following is not a property of the law of mass action?
All of the statements are properties of the law of mass action, except for the answer, which is a statement of Le Chatelier's Principle.
All of the statements are properties of the law of mass action, except for the answer, which is a statement of Le Chatelier's Principle.
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If the equilibrium constant lies farther to the right, this indicates that the reaction
.
If the equilibrium constant lies farther to the right, this indicates that the reaction .
The equilibrium constant is given by the concentraton of products over the concentration of reactants. If it lies to the right, it means that it favors the forward reaction, and thus the reaction is "more complete" or closer to completion.
The equilibrium constant is given by the concentraton of products over the concentration of reactants. If it lies to the right, it means that it favors the forward reaction, and thus the reaction is "more complete" or closer to completion.
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What is the equilbrium constant for a reaction written in reverse if the forward reaction has constant K?
What is the equilbrium constant for a reaction written in reverse if the forward reaction has constant K?
This is one of the properties of the law of mass action. The equilbrium constant for a reaction written in reverse is 1/K.
This is one of the properties of the law of mass action. The equilbrium constant for a reaction written in reverse is 1/K.
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Which of the following factors will change the equilibrium constant, Keq?
Which of the following factors will change the equilibrium constant, Keq?
The only factor that changes the equilibrium constant is temperature. Changes in concentration of reactants or products by any means (whether addition, taking away solvent, or adding a chemical that will cause side reactions) will remove the system from equilibrium, but will not change the equilibrium constant.
The only factor that changes the equilibrium constant is temperature. Changes in concentration of reactants or products by any means (whether addition, taking away solvent, or adding a chemical that will cause side reactions) will remove the system from equilibrium, but will not change the equilibrium constant.
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Consider the following reaction.
What is the reaction quotient if 
?
Consider the following reaction.
What is the reaction quotient if
The reaction quotient, or Q, of the above reaction is equal to the products over the reactants. Q is calculated in the same manner as Keq, but does not require that the reaction be at equilibrium.
The reaction quotient, or Q, of the above reaction is equal to the products over the reactants. Q is calculated in the same manner as Keq, but does not require that the reaction be at equilibrium.
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Consider the following balanced reaction.
Write the equilibrium constant expression for this reaction.
Consider the following balanced reaction.
Write the equilibrium constant expression for this reaction.
When writing an equilibrium constant expression, remember that products are on the top, and reactants are on the bottom of the expression. The coefficients for the compounds in the balanced reaction become the exponents for the compounds seen in the expression.
When writing an equilibrium constant expression, remember that products are on the top, and reactants are on the bottom of the expression. The coefficients for the compounds in the balanced reaction become the exponents for the compounds seen in the expression.
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Consider the following balanced reaction.
Write the equilibrium constant expression for this reaction.
Consider the following balanced reaction.
Write the equilibrium constant expression for this reaction.
A key point to remember is that the equilibrium constant expression only includes compounds that are in aqueous solution or in the gaseous phase. Pure solids and liquids are omitted from the expression. As a result, solid barium sulfate will not be included in the expression.
The equilibrium constant is found by the concentration of the products over the concentration of the reactants, each raised to the power of their coefficients.
In our reaction, the only reactant is a pure solid, so only the products are used in the expression.
A key point to remember is that the equilibrium constant expression only includes compounds that are in aqueous solution or in the gaseous phase. Pure solids and liquids are omitted from the expression. As a result, solid barium sulfate will not be included in the expression.
The equilibrium constant is found by the concentration of the products over the concentration of the reactants, each raised to the power of their coefficients.
In our reaction, the only reactant is a pure solid, so only the products are used in the expression.
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What is the correct equilibrium expression for this reaction?
What is the correct equilibrium expression for this reaction?
Solids are not included in any equilibrium expression. The equilibrium expression will contain only aqueous solutions and gases. In addition, the coefficients of a balanced chemical equation correspond to exponents, not coefficients, in the equilibrium expression.
For this reaction, the only relevant product is oxygen gas and the only relevant reactant is fluorine gas.
Solids are not included in any equilibrium expression. The equilibrium expression will contain only aqueous solutions and gases. In addition, the coefficients of a balanced chemical equation correspond to exponents, not coefficients, in the equilibrium expression.
For this reaction, the only relevant product is oxygen gas and the only relevant reactant is fluorine gas.
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For the following reaction, what would be the correct equilibrium expression?
For the following reaction, what would be the correct equilibrium expression?
For any equilibrium expression, solids and liquids are excluded because their concentrations are presumed to be constant during the reaction. The equilibrium expression is defined as the ratio of the concentration of products divided by the concentration of the reactants. Each reactant or product is raised to the power corresponding to its coefficient in the balanced chemical equation.
Using an arbitrary example:
Compare this to our question. Remember to exclude the solid magnesium!
For any equilibrium expression, solids and liquids are excluded because their concentrations are presumed to be constant during the reaction. The equilibrium expression is defined as the ratio of the concentration of products divided by the concentration of the reactants. Each reactant or product is raised to the power corresponding to its coefficient in the balanced chemical equation.
Using an arbitrary example:
Compare this to our question. Remember to exclude the solid magnesium!
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Determine the equation for the equilibrium constant of the following unbalanced reaction:
Determine the equation for the equilibrium constant of the following unbalanced reaction:
The equilibrium constant, 
, is the ratio of the concentration of products raised to their coefficients, over the concentration of reactants raised to their coefficients. To find its value, we first need to balance the equation and then consider only the products and reactants that actually have concentrations (i.e. aqueous and gaseous species). Liquids and solids can be omitted from the calculation.
We note that chlorine only appears once on the right, so we add a 2 coefficient to balance the equation:
Since 
is a solid (most hydroxides precipitate, unless they are paired with alkali metals, barium, or calcium) it will not be included in the equilibrium constant calculation.
The chloride ion concentration is raised to the second power because of the 2 coefficient that we added. So, putting products (species on the right side, other than the solid) on the top and reactants (species on the left) on bottom, we get:
The equilibrium constant,
We note that chlorine only appears once on the right, so we add a 2 coefficient to balance the equation:
Since
The chloride ion concentration is raised to the second power because of the 2 coefficient that we added. So, putting products (species on the right side, other than the solid) on the top and reactants (species on the left) on bottom, we get:
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Consider the following generic reaction:
If the equilibrium concentration of 
is 1M, what is the equilibrium concentration of 
?
Consider the following generic reaction:
If the equilibrium concentration of
We can set up the equilibrium expression by placing the products, raised to the power of their coefficients, in the numerator and reactants, raised to the power of their coefficients, in the denominator:
We are given the value of the equilibrium constant and the equilibrium concentration of 
. Using stoichiometric coefficients, we can determine that a variable concentration, 
, of 
will be present at equilibrium, and 
of 
will be present at equilibrium. Plugging in:
Simplify:
Now we can solve for 
(which is the equilibrium concentration of 
, as we assigned) by dividing both sides by 4 and then taking the cube root.
Rounding to 2 sig figs (to match the two numbers we were given by the problem), we get:
We can set up the equilibrium expression by placing the products, raised to the power of their coefficients, in the numerator and reactants, raised to the power of their coefficients, in the denominator:
We are given the value of the equilibrium constant and the equilibrium concentration of
Simplify:
Now we can solve for
Rounding to 2 sig figs (to match the two numbers we were given by the problem), we get:
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What is the difference between the reaction quotient and the equilibrium constant?
What is the difference between the reaction quotient and the equilibrium constant?
The correct answer gives the accurate definition of both the equilibrium constant and the reaction quotient.
The correct answer gives the accurate definition of both the equilibrium constant and the reaction quotient.
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Which of the following can always be determined based on the equation itself?
Which of the following can always be determined based on the equation itself?
According to the law of mass action, the equilibrium constant expression can always be written given the equation of the reaction itself. The equilibrium-constant expression will be written as the products over the reactants, each raised to their respectively stoichiometric coefficient. The rate law and concentrations can only be determined if there is additional data given.
According to the law of mass action, the equilibrium constant expression can always be written given the equation of the reaction itself. The equilibrium-constant expression will be written as the products over the reactants, each raised to their respectively stoichiometric coefficient. The rate law and concentrations can only be determined if there is additional data given.
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The law of mass action gives an expression that is specific for a certain
.
The law of mass action gives an expression that is specific for a certain .
Equilibrium expressions are specific for certain temperatures. Physical state, pressure, and volume do not factor into the expression.
Equilibrium expressions are specific for certain temperatures. Physical state, pressure, and volume do not factor into the expression.
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If delta G for a certain reaction is found to be -4955 J/mol, what is the equilibrium constant (Keq) for this reaction?
If delta G for a certain reaction is found to be -4955 J/mol, what is the equilibrium constant (Keq) for this reaction?
Given the equation delta G = -RTln(Keq), plugging in the correct values for the variables will lead us to the correct answer. Using e = 2.7, R = 8.314 J/molK, T= 298 K, and G = -4955 J, we can calculate that K = 7.4.
Given the equation delta G = -RTln(Keq), plugging in the correct values for the variables will lead us to the correct answer. Using e = 2.7, R = 8.314 J/molK, T= 298 K, and G = -4955 J, we can calculate that K = 7.4.
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