Introduction to Rate Law - AP Chemistry
Card 1 of 30
Identify the rate factor change if $[A]$ is doubled in $\text{rate}=k[A]^3$.
Identify the rate factor change if $[A]$ is doubled in $\text{rate}=k[A]^3$.
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$8\times$. Rate multiplies by $2^3 = 8$ when concentration doubles.
$8\times$. Rate multiplies by $2^3 = 8$ when concentration doubles.
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What are the units of $k$ for a zero-order rate law $\text{rate}=k$?
What are the units of $k$ for a zero-order rate law $\text{rate}=k$?
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$\text{mol},\text{L}^{-1},\text{s}^{-1}$. Zero-order $k$ has same units as rate itself.
$\text{mol},\text{L}^{-1},\text{s}^{-1}$. Zero-order $k$ has same units as rate itself.
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What are the units of $k$ for a second-order rate law $\text{rate}=k[A]^2$?
What are the units of $k$ for a second-order rate law $\text{rate}=k[A]^2$?
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$\text{L},\text{mol}^{-1},\text{s}^{-1}$. Second-order $k$ needs inverse concentration and time units.
$\text{L},\text{mol}^{-1},\text{s}^{-1}$. Second-order $k$ needs inverse concentration and time units.
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What is the general form of a rate law for $aA+bB\rightarrow$ products using orders $m$ and $n$?
What is the general form of a rate law for $aA+bB\rightarrow$ products using orders $m$ and $n$?
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$\text{rate}=k[A]^m[B]^n$. Shows how rate depends on concentrations raised to experimental powers.
$\text{rate}=k[A]^m[B]^n$. Shows how rate depends on concentrations raised to experimental powers.
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What does the rate constant $k$ represent in a rate law?
What does the rate constant $k$ represent in a rate law?
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Proportionality constant relating rate to reactant concentrations. Links reaction rate to concentrations through multiplication.
Proportionality constant relating rate to reactant concentrations. Links reaction rate to concentrations through multiplication.
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What is the overall reaction order for $\text{rate}=k[A]^m[B]^n$?
What is the overall reaction order for $\text{rate}=k[A]^m[B]^n$?
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$m+n$. Sum of all individual reaction orders gives overall order.
$m+n$. Sum of all individual reaction orders gives overall order.
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Which statement is correct: reaction orders come from stoichiometric coefficients or from experiment?
Which statement is correct: reaction orders come from stoichiometric coefficients or from experiment?
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From experiment (not from overall stoichiometric coefficients). Orders must be determined experimentally, not from balanced equation.
From experiment (not from overall stoichiometric coefficients). Orders must be determined experimentally, not from balanced equation.
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What does it mean if a reactant is zero order in the rate law?
What does it mean if a reactant is zero order in the rate law?
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Rate is independent of that reactant’s concentration. Zero power means concentration changes don't affect rate.
Rate is independent of that reactant’s concentration. Zero power means concentration changes don't affect rate.
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What does it mean if a reactant is first order in the rate law?
What does it mean if a reactant is first order in the rate law?
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Doubling its concentration doubles the rate. First power means rate changes proportionally with concentration.
Doubling its concentration doubles the rate. First power means rate changes proportionally with concentration.
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What does it mean if a reactant is second order in the rate law?
What does it mean if a reactant is second order in the rate law?
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Doubling its concentration quadruples the rate. Second power means rate changes with concentration squared.
Doubling its concentration quadruples the rate. Second power means rate changes with concentration squared.
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What is the rate law for an elementary step $A+B\rightarrow$ products?
What is the rate law for an elementary step $A+B\rightarrow$ products?
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$\text{rate}=k[A][B]$. Elementary steps use stoichiometric coefficients as orders.
$\text{rate}=k[A][B]$. Elementary steps use stoichiometric coefficients as orders.
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What is the rate law for an elementary unimolecular step $A\rightarrow$ products?
What is the rate law for an elementary unimolecular step $A\rightarrow$ products?
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$\text{rate}=k[A]$. Single molecule reactions are first order in that reactant.
$\text{rate}=k[A]$. Single molecule reactions are first order in that reactant.
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What is the rate law for an elementary termolecular step $A+B+C\rightarrow$ products?
What is the rate law for an elementary termolecular step $A+B+C\rightarrow$ products?
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$\text{rate}=k[A][B][C]$. Three-molecule collisions give third-order rate law.
$\text{rate}=k[A][B][C]$. Three-molecule collisions give third-order rate law.
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What is the rate law for an elementary step $2A\rightarrow$ products?
What is the rate law for an elementary step $2A\rightarrow$ products?
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$\text{rate}=k[A]^2$. Two identical molecules reacting gives second-order dependence.
$\text{rate}=k[A]^2$. Two identical molecules reacting gives second-order dependence.
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What is the definition of rate in terms of concentration change for reactant $A$ in $aA\rightarrow$ products?
What is the definition of rate in terms of concentration change for reactant $A$ in $aA\rightarrow$ products?
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$\text{rate}=-\frac{1}{a}\frac{d[A]}{dt}$. Negative sign shows reactant concentration decreases over time.
$\text{rate}=-\frac{1}{a}\frac{d[A]}{dt}$. Negative sign shows reactant concentration decreases over time.
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What is the definition of rate in terms of concentration change for product $P$ in $\rightarrow pP$?
What is the definition of rate in terms of concentration change for product $P$ in $\rightarrow pP$?
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$\text{rate}=\frac{1}{p}\frac{d[P]}{dt}$. Positive derivative shows product concentration increases over time.
$\text{rate}=\frac{1}{p}\frac{d[P]}{dt}$. Positive derivative shows product concentration increases over time.
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What are the units of rate for concentration in $\text{mol},\text{L}^{-1}$ and time in seconds?
What are the units of rate for concentration in $\text{mol},\text{L}^{-1}$ and time in seconds?
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$\text{mol},\text{L}^{-1},\text{s}^{-1}$. Rate measures concentration change per unit time.
$\text{mol},\text{L}^{-1},\text{s}^{-1}$. Rate measures concentration change per unit time.
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What are the units of $k$ for a first-order rate law $\text{rate}=k[A]$?
What are the units of $k$ for a first-order rate law $\text{rate}=k[A]$?
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$\text{s}^{-1}$. First-order $k$ has time inverse units only.
$\text{s}^{-1}$. First-order $k$ has time inverse units only.
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Identify the rate factor change if $[A]$ is halved in $\text{rate}=k[A]^2$.
Identify the rate factor change if $[A]$ is halved in $\text{rate}=k[A]^2$.
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$\frac{1}{4}\times$. Rate multiplies by $(\frac{1}{2})^2 = \frac{1}{4}$ when concentration halves.
$\frac{1}{4}\times$. Rate multiplies by $(\frac{1}{2})^2 = \frac{1}{4}$ when concentration halves.
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Identify the overall order for $\text{rate}=k[A]^{\frac{1}{2}}[B]^{\frac{3}{2}}$.
Identify the overall order for $\text{rate}=k[A]^{\frac{1}{2}}[B]^{\frac{3}{2}}$.
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$2$. Add exponents: $\frac{1}{2} + \frac{3}{2} = 2$.
$2$. Add exponents: $\frac{1}{2} + \frac{3}{2} = 2$.
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What are the units of $k$ for a zero-order rate law $\text{rate} = k$?
What are the units of $k$ for a zero-order rate law $\text{rate} = k$?
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$\text{M},\text{s}^{-1}$. Units: $k = \text{rate}$ since no concentration dependence.
$\text{M},\text{s}^{-1}$. Units: $k = \text{rate}$ since no concentration dependence.
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Identify $m$ if doubling $[A]$ makes the rate double (with other reactants constant).
Identify $m$ if doubling $[A]$ makes the rate double (with other reactants constant).
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$m = 1$. Rate doubles means $(2)^m = 2$, so $m = 1$.
$m = 1$. Rate doubles means $(2)^m = 2$, so $m = 1$.
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What is the method called that uses two trials to solve for reaction orders from rate data?
What is the method called that uses two trials to solve for reaction orders from rate data?
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Method of initial rates. Compares initial rates at different concentrations to find orders.
Method of initial rates. Compares initial rates at different concentrations to find orders.
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Identify $m$ if doubling $[A]$ makes the rate quadruple (with other reactants constant).
Identify $m$ if doubling $[A]$ makes the rate quadruple (with other reactants constant).
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$m = 2$. Rate quadruples means $(2)^m = 4$, so $m = 2$.
$m = 2$. Rate quadruples means $(2)^m = 4$, so $m = 2$.
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Identify $m$ if doubling $[A]$ makes the rate unchanged (with other reactants constant).
Identify $m$ if doubling $[A]$ makes the rate unchanged (with other reactants constant).
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$m = 0$. Rate unchanged means $(2)^m = 1$, so $m = 0$.
$m = 0$. Rate unchanged means $(2)^m = 1$, so $m = 0$.
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What is the overall reaction order for $\text{rate} = k[A]^2[B]^1$?
What is the overall reaction order for $\text{rate} = k[A]^2[B]^1$?
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$3$. Sum all exponents: $2 + 1 = 3$.
$3$. Sum all exponents: $2 + 1 = 3$.
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What does the rate constant $k$ represent in a rate law?
What does the rate constant $k$ represent in a rate law?
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Proportionality constant relating rate to reactant concentrations. Links reaction rate to concentrations; temperature-dependent.
Proportionality constant relating rate to reactant concentrations. Links reaction rate to concentrations; temperature-dependent.
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What is the general form of the rate law for $aA + bB \to$ products?
What is the general form of the rate law for $aA + bB \to$ products?
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$\text{rate} = k[A]^m[B]^n$. Exponents $m$ and $n$ are reaction orders, not stoichiometric coefficients.
$\text{rate} = k[A]^m[B]^n$. Exponents $m$ and $n$ are reaction orders, not stoichiometric coefficients.
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What are the units of reaction rate when concentration is in $\text{M}$ and time is in seconds?
What are the units of reaction rate when concentration is in $\text{M}$ and time is in seconds?
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$\text{M},\text{s}^{-1}$. Rate is change in concentration per unit time.
$\text{M},\text{s}^{-1}$. Rate is change in concentration per unit time.
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What are the units of $k$ for a first-order rate law $\text{rate} = k[A]$?
What are the units of $k$ for a first-order rate law $\text{rate} = k[A]$?
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$\text{s}^{-1}$. Units: $\frac{\text{M},\text{s}^{-1}}{\text{M}} = \text{s}^{-1}$.
$\text{s}^{-1}$. Units: $\frac{\text{M},\text{s}^{-1}}{\text{M}} = \text{s}^{-1}$.
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