Questions and Answers
What does the rate of a reaction measure?
What does a negative ∆G indicate about a reaction?
It indicates that the reaction is spontaneous.
Spontaneity of a reaction is related to its speed.
False
What is the general form of a rate equation?
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The slope of the concentration vs time plot generally approaches _____ as the reaction approaches equilibrium.
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What happens to reactant concentration as time goes on?
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Match the following concepts with their definitions:
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What can the order of a reaction with respect to a particular species be defined as?
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Study Notes
Rates of Chemical Reactions
- Reaction rate reflects the speed of reactant consumption or product formation.
- Rate is quantified as the change in concentration over time.
- Rate Law relates the rate of a reaction to the rate constant and reactant concentrations.
- Reaction orders indicate how the rate depends on the concentration of reactants.
Spontaneity and Reaction Speed
- A reaction is spontaneous if the Gibbs free energy change (∆G) is negative.
- Spontaneity indicates thermodynamic favorability, not speed.
- Example: The transformation of diamond to graphite is spontaneous but extremely slow.
Rate Equation
- General form of the rate equation: Rate = k(reactants).
- Differential rate law example: (-\frac{d[A]}{dt} = k[A][B]).
- The rate constant (k) is specific to each reaction and influenced by various factors.
Empirical Observations of Reaction Rates
- Observing how reactant and product concentrations change over time is fundamental in kinetics.
- L. Wilhelm's study in 1850 laid groundwork through the inversion of sucrose with a polarimeter.
- Various methods for measuring concentration include spectrophotometry and potentiometry.
Concentration Over Time
- As a reaction progresses, reactant concentration decreases while product concentration increases.
- Intermediate species may appear and then disappear during reaction progress.
Rate Change and Stoichiometry
- For a generalized reaction (aA + bB \rightarrow cC + dD), the rate law reflects the relationship between reactants and products.
- The rate at which products form is calculated as (\frac{1}{c} \frac{d[C]}{dt} = f[A][B][C][D]).
- Rates for other species are related by the stoichiometric coefficients.
Order of Reaction
- Overall order of a reaction is the sum of the powers of reactants in the rate law.
- Reaction order indicates how the rate depends on each reactant's concentration.
Experimental Determination of Reaction Order
- For the reaction: (F_2(g) + 2 ClO_2(g) \rightarrow 2FClO_2(g)), data collection includes concentration values and initial rates for various experiments.
- Initial rate dependence on ([F_2]) and ([ClO_2]) can help deduce reaction orders.
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Description
This quiz covers fundamental concepts in chemical kinetics, including reaction rates, rate laws, and spontaneity of reactions. It examines how reaction rates are quantified and the relationship between concentration and reaction speed. Test your understanding of these principles and their applications.
