Properties of the Equilibrium Constant - AP Chemistry
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What is the equilibrium-constant expression for $aA+bB\rightleftharpoons cC+dD$ using concentrations?
What is the equilibrium-constant expression for $aA+bB\rightleftharpoons cC+dD$ using concentrations?
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$K_c=\frac{[C]^c[D]^d}{[A]^a[B]^b}$. Products over reactants, each raised to its stoichiometric coefficient.
$K_c=\frac{[C]^c[D]^d}{[A]^a[B]^b}$. Products over reactants, each raised to its stoichiometric coefficient.
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What happens to $K$ when the initial concentrations or partial pressures are changed at constant temperature?
What happens to $K$ when the initial concentrations or partial pressures are changed at constant temperature?
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$K$ is unchanged. K depends only on temperature, not on initial conditions.
$K$ is unchanged. K depends only on temperature, not on initial conditions.
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What is the only common experimental change that can change $K$ for a given reaction?
What is the only common experimental change that can change $K$ for a given reaction?
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Changing temperature. K is a function of temperature only for a given reaction.
Changing temperature. K is a function of temperature only for a given reaction.
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What is the sign of $\Delta G^\circ$ when $K<1$ at a given temperature?
What is the sign of $\Delta G^\circ$ when $K<1$ at a given temperature?
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$\Delta G^\circ>0$. Since $\ln K < 0$ when $K < 1$, $\Delta G^\circ$ must be positive.
$\Delta G^\circ>0$. Since $\ln K < 0$ when $K < 1$, $\Delta G^\circ$ must be positive.
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What is the sign of $\Delta G^\circ$ when $K>1$ at a given temperature?
What is the sign of $\Delta G^\circ$ when $K>1$ at a given temperature?
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$\Delta G^\circ<0$. Since $\ln K > 0$ when $K > 1$, $\Delta G^\circ$ must be negative.
$\Delta G^\circ<0$. Since $\ln K > 0$ when $K > 1$, $\Delta G^\circ$ must be negative.
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What is the relationship between $K$ and $\Delta G^\circ$ at a given temperature?
What is the relationship between $K$ and $\Delta G^\circ$ at a given temperature?
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$\Delta G^\circ=-RT\ln K$. Links thermodynamic favorability to equilibrium position.
$\Delta G^\circ=-RT\ln K$. Links thermodynamic favorability to equilibrium position.
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What is $\Delta n$ in the formula $K_p=K_c(RT)^{\Delta n}$ for a gas-phase reaction?
What is $\Delta n$ in the formula $K_p=K_c(RT)^{\Delta n}$ for a gas-phase reaction?
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$\Delta n=\text{mol gas products}-\text{mol gas reactants}$. Counts net change in moles of gas from reactants to products.
$\Delta n=\text{mol gas products}-\text{mol gas reactants}$. Counts net change in moles of gas from reactants to products.
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What is the general rule for how $K$ changes when a reaction is reversed?
What is the general rule for how $K$ changes when a reaction is reversed?
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$K_{\text{rev}}=\frac{1}{K}$. Reversing flips products and reactants, so K becomes its reciprocal.
$K_{\text{rev}}=\frac{1}{K}$. Reversing flips products and reactants, so K becomes its reciprocal.
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What is the relationship between $K_p$ and $K_c$ for ideal gases in terms of $\Delta n$?
What is the relationship between $K_p$ and $K_c$ for ideal gases in terms of $\Delta n$?
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$K_p=K_c(RT)^{\Delta n}$. Relates pressure and concentration equilibrium constants via ideal gas law.
$K_p=K_c(RT)^{\Delta n}$. Relates pressure and concentration equilibrium constants via ideal gas law.
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What is the activity value used for any pure solid or pure liquid in an equilibrium expression?
What is the activity value used for any pure solid or pure liquid in an equilibrium expression?
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$1$. Pure solids and liquids have unit activity by definition.
$1$. Pure solids and liquids have unit activity by definition.
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Identify the correct $K_p$ if $K_c=0.50$, $\Delta n=2$, and $RT=25$ for an ideal-gas reaction.
Identify the correct $K_p$ if $K_c=0.50$, $\Delta n=2$, and $RT=25$ for an ideal-gas reaction.
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$312.5$. $K_p = 0.50 × 25^2 = 312.5$ using $K_p = K_c(RT)^{\Delta n}$
$312.5$. $K_p = 0.50 × 25^2 = 312.5$ using $K_p = K_c(RT)^{\Delta n}$
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Identify the correct $K$ for the overall reaction if $K_1=2.0\times10^3$ and $K_2=5.0\times10^{-2}$ are added.
Identify the correct $K$ for the overall reaction if $K_1=2.0\times10^3$ and $K_2=5.0\times10^{-2}$ are added.
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$1.0\times10^2$. $K_{\text{overall}} = (2.0×10^3)(5.0×10^{-2}) = 1.0×10^2$
$1.0\times10^2$. $K_{\text{overall}} = (2.0×10^3)(5.0×10^{-2}) = 1.0×10^2$
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Identify the correct $K$ when $K=3.0$ and the balanced equation coefficients are doubled.
Identify the correct $K$ when $K=3.0$ and the balanced equation coefficients are doubled.
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$9.0$. $K_{\text{new}} = 3.0^2 = 9.0$ when coefficients are doubled.
$9.0$. $K_{\text{new}} = 3.0^2 = 9.0$ when coefficients are doubled.
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Identify the correct $K$ when $K=4.0$ for $A\rightleftharpoons B$ and the reaction is reversed.
Identify the correct $K$ when $K=4.0$ for $A\rightleftharpoons B$ and the reaction is reversed.
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$0.25$. $K_{\text{rev}} = \frac{1}{4.0} = 0.25$ by the reversal rule.
$0.25$. $K_{\text{rev}} = \frac{1}{4.0} = 0.25$ by the reversal rule.
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Which species are omitted from $K$ expressions for heterogeneous equilibria: pure solids, pure liquids, or both?
Which species are omitted from $K$ expressions for heterogeneous equilibria: pure solids, pure liquids, or both?
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Both pure solids and pure liquids are omitted. Their activities are constant at 1, so they don't affect K.
Both pure solids and pure liquids are omitted. Their activities are constant at 1, so they don't affect K.
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What is the equilibrium-constant expression for $aA+bB\rightleftharpoons cC+dD$ using partial pressures?
What is the equilibrium-constant expression for $aA+bB\rightleftharpoons cC+dD$ using partial pressures?
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$K_p=\frac{(P_C)^c(P_D)^d}{(P_A)^a(P_B)^b}$. Same form as $K_c$ but uses partial pressures instead of concentrations.
$K_p=\frac{(P_C)^c(P_D)^d}{(P_A)^a(P_B)^b}$. Same form as $K_c$ but uses partial pressures instead of concentrations.
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Identify the correct $K$ if $\Delta G^\circ=0$ at a given temperature.
Identify the correct $K$ if $\Delta G^\circ=0$ at a given temperature.
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$1$. When $\Delta G^\circ = 0$, then $\ln K = 0$, so $K = 1$.
$1$. When $\Delta G^\circ = 0$, then $\ln K = 0$, so $K = 1$.
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What is the general rule for how $K$ changes when all coefficients are multiplied by $n$?
What is the general rule for how $K$ changes when all coefficients are multiplied by $n$?
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$K_{\text{new}}=K^n$. Multiplying coefficients by n raises K to the nth power.
$K_{\text{new}}=K^n$. Multiplying coefficients by n raises K to the nth power.
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What is the general rule for how $K$ changes when two reactions are added to give an overall reaction?
What is the general rule for how $K$ changes when two reactions are added to give an overall reaction?
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$K_{\text{overall}}=K_1K_2$. When reactions add, their equilibrium constants multiply.
$K_{\text{overall}}=K_1K_2$. When reactions add, their equilibrium constants multiply.
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What is the relationship between $K_p$ and $K_c$ for gases using $\Delta n_{\text{gas}}$?
What is the relationship between $K_p$ and $K_c$ for gases using $\Delta n_{\text{gas}}$?
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$K_p=K_c(RT)^{\Delta n_{\text{gas}}}$. Relates pressure and concentration constants via ideal gas law.
$K_p=K_c(RT)^{\Delta n_{\text{gas}}}$. Relates pressure and concentration constants via ideal gas law.
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How does $K$ change if all coefficients in the balanced reaction are multiplied by $n$?
How does $K$ change if all coefficients in the balanced reaction are multiplied by $n$?
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$K_{\text{new}}=K^n$. Each species' exponent multiplies by $n$, so $K$ raises to $n$.
$K_{\text{new}}=K^n$. Each species' exponent multiplies by $n$, so $K$ raises to $n$.
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How does $K$ change if the balanced reaction is reversed?
How does $K$ change if the balanced reaction is reversed?
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$K_{\text{rev}}=\frac{1}{K}$. Reversing swaps products and reactants, inverting $K$.
$K_{\text{rev}}=\frac{1}{K}$. Reversing swaps products and reactants, inverting $K$.
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What is the value of the activity used for any pure solid or pure liquid in an equilibrium expression?
What is the value of the activity used for any pure solid or pure liquid in an equilibrium expression?
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$a=1$. By definition, pure solids/liquids have unit activity.
$a=1$. By definition, pure solids/liquids have unit activity.
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Which species are omitted from $K$ for a heterogeneous equilibrium: pure solids, pure liquids, or aqueous solutes?
Which species are omitted from $K$ for a heterogeneous equilibrium: pure solids, pure liquids, or aqueous solutes?
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Pure solids and pure liquids are omitted. Their activities equal 1, so they don't affect $K$.
Pure solids and pure liquids are omitted. Their activities equal 1, so they don't affect $K$.
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What is the general equilibrium constant expression $K_p$ for $aA+bB\rightleftharpoons cC+dD$ (gases)?
What is the general equilibrium constant expression $K_p$ for $aA+bB\rightleftharpoons cC+dD$ (gases)?
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$K_p=\frac{(P_C)^c(P_D)^d}{(P_A)^a(P_B)^b}$. Uses partial pressures instead of concentrations for gases.
$K_p=\frac{(P_C)^c(P_D)^d}{(P_A)^a(P_B)^b}$. Uses partial pressures instead of concentrations for gases.
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What is the general equilibrium constant expression $K_c$ for $aA+bB\rightleftharpoons cC+dD$?
What is the general equilibrium constant expression $K_c$ for $aA+bB\rightleftharpoons cC+dD$?
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$K_c=\frac{[C]^c[D]^d}{[A]^a[B]^b}$. Products raised to stoichiometric coefficients over reactants.
$K_c=\frac{[C]^c[D]^d}{[A]^a[B]^b}$. Products raised to stoichiometric coefficients over reactants.
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Find $K$ for $\frac{1}{2}\times$ the reaction if the original reaction has $K=1.6\times10^{-5}$.
Find $K$ for $\frac{1}{2}\times$ the reaction if the original reaction has $K=1.6\times10^{-5}$.
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$K_{\text{new}}=4.0\times10^{-3}$. $K_{\text{new}}=(1.6\times10^{-5})^{1/2}=4.0\times10^{-3}$.
$K_{\text{new}}=4.0\times10^{-3}$. $K_{\text{new}}=(1.6\times10^{-5})^{1/2}=4.0\times10^{-3}$.
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Find $K_{\text{rev}}$ if $K=5.0\times10^{-4}$ for the forward reaction.
Find $K_{\text{rev}}$ if $K=5.0\times10^{-4}$ for the forward reaction.
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$K_{\text{rev}}=2.0\times10^3$. $K_{\text{rev}}=\frac{1}{5.0\times10^{-4}}=2.0\times10^3$.
$K_{\text{rev}}=2.0\times10^3$. $K_{\text{rev}}=\frac{1}{5.0\times10^{-4}}=2.0\times10^3$.
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Identify the equilibrium direction if $K=4.0\times10^{-6}$ for a reaction written as products over reactants.
Identify the equilibrium direction if $K=4.0\times10^{-6}$ for a reaction written as products over reactants.
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Reactant-favored (equilibrium lies to the left). $K<<1$ means reactants predominate at equilibrium.
Reactant-favored (equilibrium lies to the left). $K<<1$ means reactants predominate at equilibrium.
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Identify the equilibrium direction if $K=2.0\times10^3$ for a reaction written as products over reactants.
Identify the equilibrium direction if $K=2.0\times10^3$ for a reaction written as products over reactants.
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Product-favored (equilibrium lies to the right). $K>>1$ means products predominate at equilibrium.
Product-favored (equilibrium lies to the right). $K>>1$ means products predominate at equilibrium.
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