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AP Chemistry: Reaction Rates

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Section 1

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Instantaneous Reaction

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Chemistry Science

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Mar 1, 2020

Cards (19)

Section 1

(19 cards)

Instantaneous Reaction

Front

This refers to the rate of a reaction at a specific time. This can be shown by a graph displaying concentration vs time, the slope being a specific time. You can find the rate at a specific concentration if you know the rate law constant, k. Note: Sample problem on page 15 of notes packet!

Back

Energy Profile Charts

Front

Shows activation energy, activation complex, and reveals whether a reaction is endothermic (Products have more energy than activation energy.) or exothermic. (Products have less energy than activation energy.)

Back

Reaction Rate (2)

Front

( [A] at t^2 ) - ( [A] at t^1 )/ t^2 - t^1

Back

One-step Reaction (A -> B)

Front

Rate = k [A] ; [A] is the concentration of reactant A, while k is a constant of mol/s. As [A] increases, rate increases. Furthermore, if [A] decreases, rate decreases as well. Note: [A] = [A]^1, and x^0 = 1. Reaction rate and reaction order are determined experimentally.

Back

Rate Determining Step

Front

The slowest elementary step determines the rate of the complex reaction. "You're as strong as your weakest link." Knowing the rate determining step can help chemists either speed up the reaction with a catalyst, or slow it down with an inhibitor.

Back

Factors of Chemical Reactions

Front

Activation Energy (high -> slow, low -> fast); structure and electron configuration (Do they bond at all?); concentration (more particles to collide with); surface area (more areas to collide); temperature (particles move faster, increasing chances of collision);

Back

Reaction Rate

Front

Change in Concentration/Change in Time (Concentration divided by Time)

Back

Activation Energy, Ea

Front

Activation energy is the minimum amount of energy needed to form the activated complex. This strongly effects the rate of reactions. High activation energy causes slower reactions, because particles need to reach the activation energy. Low activation is the opposite, causing fast reactions, as particles can easy reach the activation energy minimum.

Back

Reaction Mechanisms

Front

Most chemical reactions consist of a sequence of two or more simpler reactions, called elementary steps. The overall reaction is called a complex reaction. Note: Sample problem on page 15 of notes packet!

Back

Intermediate

Front

These are the elementary steps of a complex reaction you can cancel out, similar to in math. A product is made in one step, then used in another, cancelling it out.

Back

First Order Reactions

Front

( ln [A]t ) = -kt + ( ln [A]0 ) Remember, ln is natural log, countered by e. Note: Sample problem on page 14 of notes packet!

Back

Catalysts

Front

Catalysts speed up chemical reactions by lowering activation energy without actually participating in the reaction itself. A natural, biological catalysts our own bodies have are enzymes, which are comparable to puzzle pieces.

Back

Rate Law/Reaction Order

Front

Rate = k [A]^m [B]^n ; The deals with initial rates by comparing rates with concentrations. Rate = k [A]^1 is a first order in [A]. Rate = k [A]^3 is a third order in [A]. Rate = k [A]^1[B]^2 is a first order in [A], a second order in [B], and a third order overall. Note: Sample problem on page 12 of notes packet!

Back

Inhibitor

Front

Unlike a catalyst, inhibitors inhibit, or slow down, a reaction. A common inhibitor many know are food preservatives, such as in meat, meant to slow down rotting, or to stop it completely.

Back

Second Order Reactions

Front

1 / ( [A]t ) = kt + ( 1 / ( [A]0 ) ) Remember, ln is natural log, countered by e.

Back

Examples of Fast Reactions

Front

instantaneous combustion

Back

Collision Theory

Front

Theory that atoms, molecules and ions must collide to react. Orientation is also important for this to occur.

Back

Activated Complex

Front

This is an intermediate substance formed during the reaction. It can either form products, stay together separately, or break apart.

Back

Examples of Slow Reactions

Front

rusting

Back