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Kinetics in Chemistry Flashcards

Kinetics in Chemistry Flashcards
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How entropy changes as state of matter changes.
Solid has least entropy. Liquid has more entropy than solid. Gas has more entropy than liquid.
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Define the term: state function
A property that'll be the same whatever path was taken to achieve the current state.
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How entropy change (S) affects change in Gibbs Free Energy (Delta G)
Increased S means a negative Delta G when enthalpy decreases OR at low temperatures. Reduced S means a positive Delta G when enthalpy increases OR at high temperatures.
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How enthalpy change affects Gibbs Free Energy
When enthalpy increases, the change in Gibbs Free Energy (delta G) will be positive (non-spontaneous) when entropy decreases, OR at low temperatures when entropy increases.
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The unit of temperature measurement used when calculating Gibbs Free Energy.
Kelvin
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What the equilibrium constant (k) signifies
Large k means a spontaneous reaction. Small k means a non-spontaneous reaction. A k around 1 means equilibrium.
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In Hess's Law, how the enthalpy change (delta H) changes when you use the reverse of a reaction
Use the same magnitude (number) but flip the +/- sign.
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In Hess's Law, how the enthalpy change (delta H) changes when you multiply one step by an integer.
Multiply the delta H by that integer too.
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Define the term: thermochemical equation
A chemical equation that also provides the change in enthalpy (delta H) for the reaction.
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Define Hess's Law
You can find the enthalpy change for a reaction by adding up the enthalpy changes of the steps in the reaction.
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What water's specific heat capacity means
It's relatively high, so water changes temperature relatively slowly. Lakes and rivers stay liquid in fairly cold temperatures.
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What it means to have a high specific heat capacity
It means that substance requires a lot of heat input in order to change its temperature.
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How you find the specific heat capacity of a substance to use in calculations
It will be provided, or you can look it up in a table.
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Equation for the amount of heat needed to raise a substance's temperature by a certain amount, and what each term means.
Q = s * m * (Delta T), where Q = heat or energy, s = the specific heat capacity of the substance, m = mass of substance, & Delta T = change in temperature in degrees Celsius.
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Define the term: specific heat capacity
How much heat you need to make 1 gram of a certain substance be 1 Celsius degree hotter.
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Define the term: homogeneous reaction
A reaction whose reactants and products are all in the same state of matter (solid, liquid, or gas).
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Define the term 'intermediates' in the context of a chemical reaction
Middle-step compounds created during the reaction that then change to something else. They aren't reactants or products.
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Meaning of a rate order of 2
The rate is proportional to the square of the concentration of this reactant.
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Meaning of a rate order of 1
The rate is directly proportional to the concentration of this reactant.
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Meaning of a rate order of 0
Concentration of the reactant does not affect the rate of the reaction.
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40 cards in set

Flashcard Content Overview

This set of flashcards covers kinetics and thermodynamics. You can learn how to determine the rate of a reaction, and what it means for a reaction to be spontaneous. These cards can also help you remember how to calculate Gibbs Free Energy, which tells us the amount of energy that a reaction produces, and how enthalpy and entropy affect that quantity. And you'll review concepts like Hess's Law and the equilibrium constant.

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Meaning of a rate order of 0
Concentration of the reactant does not affect the rate of the reaction.
Meaning of a rate order of 1
The rate is directly proportional to the concentration of this reactant.
Meaning of a rate order of 2
The rate is proportional to the square of the concentration of this reactant.
Define the term 'intermediates' in the context of a chemical reaction
Middle-step compounds created during the reaction that then change to something else. They aren't reactants or products.
Define the term: homogeneous reaction
A reaction whose reactants and products are all in the same state of matter (solid, liquid, or gas).
Define the term: specific heat capacity
How much heat you need to make 1 gram of a certain substance be 1 Celsius degree hotter.
Equation for the amount of heat needed to raise a substance's temperature by a certain amount, and what each term means.
Q = s * m * (Delta T), where Q = heat or energy, s = the specific heat capacity of the substance, m = mass of substance, & Delta T = change in temperature in degrees Celsius.
How you find the specific heat capacity of a substance to use in calculations
It will be provided, or you can look it up in a table.
What it means to have a high specific heat capacity
It means that substance requires a lot of heat input in order to change its temperature.
What water's specific heat capacity means
It's relatively high, so water changes temperature relatively slowly. Lakes and rivers stay liquid in fairly cold temperatures.
Define Hess's Law
You can find the enthalpy change for a reaction by adding up the enthalpy changes of the steps in the reaction.
Define the term: thermochemical equation
A chemical equation that also provides the change in enthalpy (delta H) for the reaction.
In Hess's Law, how the enthalpy change (delta H) changes when you multiply one step by an integer.
Multiply the delta H by that integer too.
In Hess's Law, how the enthalpy change (delta H) changes when you use the reverse of a reaction
Use the same magnitude (number) but flip the +/- sign.
What the equilibrium constant (k) signifies
Large k means a spontaneous reaction. Small k means a non-spontaneous reaction. A k around 1 means equilibrium.
The unit of temperature measurement used when calculating Gibbs Free Energy.
Kelvin
How enthalpy change affects Gibbs Free Energy
When enthalpy increases, the change in Gibbs Free Energy (delta G) will be positive (non-spontaneous) when entropy decreases, OR at low temperatures when entropy increases.
How entropy change (S) affects change in Gibbs Free Energy (Delta G)
Increased S means a negative Delta G when enthalpy decreases OR at low temperatures. Reduced S means a positive Delta G when enthalpy increases OR at high temperatures.
Define the term: state function
A property that'll be the same whatever path was taken to achieve the current state.
How entropy changes as state of matter changes.
Solid has least entropy. Liquid has more entropy than solid. Gas has more entropy than liquid.
How temperature affects entropy
Higher temperature means more entropy.
The formula for Gibbs Free Energy, and what each term means
G = H - TS. G is free energy. H is enthalpy. T is temperature. S is entropy.
The significance of the change in Gibbs Free Energy (Delta G)
This tells us how much useful energy a reaction produces, which we can harness for doing work. Negative Delta G means the reaction is spontaneous. Positive Delta G means it is nonspontaneous.
Define the term: spontaneous energy, and state its delta G (change in Gibbs Free Energy)
A reaction that happens on its own. Delta G is negative. Spontaneity depends on the temperature. Spontaneous doesn't mean fast.
Define the term: endothermic
A reaction that needs heat input to proceed. This requires an increase of enthalpy to the system.
Define the term: enthalpy change
How much heat/energy a process will take in or give off
Define the term: exothermic
A reaction that gives off heat. This reduces the amount of enthalpy in the system.
This is the role of the cathode in an electrochemical cell
To receive electrons from the anode
Define the term: reaction mechanism
Name for the series of events or steps in a chemical reaction
Units of reaction rate
Concentration change per unit of time. Sometimes change-of-Molarity per second, sometimes change-of-molarity per minute.
How temperature affects the rate constant k
Higher temperatures usually mean a higher k and a faster reaction.
How to calculate the rate constant k, and what each term means
k = A * e^(-Ea/RT). Ea = activation energy. A = How often reactants get near Ea. e = fraction of reactants that achieve Ea. T = temperature (Kelvin). R = 8.314 J/mol k
How to determine rate order
Only experimentally, by gathering data, not by looking at the reaction equation.
Define the term: reaction order
A term that describes whether and how the reactant concentration affects the reaction rate. It's determined experimentally.
The formula for the rate law with one reactant, and what each term means.
Rate = k * A^m. k is the rate constant. A is the concentration of reactant. m is the reaction order.
Define the term: activation energy
An amount of energy that is needed to start a chemical reaction. It looks like a hill on a graph of energy.
How many different rate constants there are
Lots! They're different for each reaction at each temperature.
Reaction rate
A value that describes how quickly a reaction will happen
Units of the rate constant k
Depends on the reaction order. Must be in units that result in the rate being molarity per unit of time (typically seconds). Units of M^(-n)/s, where n is the reaction order.
The equation you would use to determine the spontaneity of a reaction knowing its enthalpy and entropy changes
G = H - TS

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