Rates of Reaction

Flashcards for vocabulary related to rates of reaction.

Rate of Reaction

The speed at which chemical reactions occur.

Objectives of Studying Rates of Reaction

Define rate of reaction, identify affecting factors, predict effects on rates, interpret graphical data.

Rate of Reaction Definition

The speed at which a chemical reaction occurs.

Measuring Rates of Reaction - Reactants

Concentration of reactants decreases during a reaction.

Measuring Rates of Reaction - Products

Concentration of products increases during a reaction.

Determining Rate of Reaction

Measure decrease in reactant concentration or increase in product concentration over time.

Volume of Gas Produced

A property to measure rates of reaction when one of the products is a gas.

Decrease in Mass

A property to measure rates of reaction if a product is a gas allowed to escape.

Precipitate Formation

Appearance of a precipitate can be measured to determine rate of reaction.

Collision Theory

Chemical reactions involve breaking original bonds in reactants and forming new bonds in products.

Conditions for Reaction - Collision

Reactant particles must collide with each other.

Conditions for Reaction - Activation Energy

Reactant particles must collide with enough activation energy.

Conditions for Reaction - Orientation

Reactant particles must collide with the correct orientation.

Effective Collision

Collisions that result in a reaction when all three factors are met.

Rate of Reaction Dependence

The rate of reaction depends on the number of effective collisions occuring.

General Shape of Rate Curves

Rate curves have the same basic shape when a measured property is plotted against time.

Rate Curve - Beginning

The gradient is steepest, indicating the reaction rate is highest at the beginning.

Rate Curve - Proceeding

The gradient becomes shallower, indicating the reaction rate is decreasing as the reaction proceeds.

Rate Curve - End

The curve becomes horizontal, the gradient becomes zero, indicating the reaction has reached completion.

Limiting Reactant

The reactant that is used up first.

Factors Affecting Reaction Rate

Includes temperature, concentration, surface area, and catalysts.

Photochemical Reactions

Reactions initiated by light.

Pressure Effect

Increasing pressure on gaseous reactants increases the rate of reaction.

Temperature Rule

The higher the temperature, the higher the rate of reaction.

Increased Temperature Explanation

Reactant particles gain kinetic energy and move faster.

Temperature Graphical

Graph of rate of reaction against temperature is an upward curve.

Concentration Rule

The higher the concentration of the reactant, the higher the rate of reaction.

Concentration Explanation

Increasing reactant concentration increases reactant particles per unit volume.

Concentration Graphical

Graph of rate of reaction against concentration is a straight line.

Surface Area Rule

The smaller the particles of a reactant, the higher the rate of reaction.

Surface Area Explanation

Small solid particles have a larger total surface area.

Catalyst

A chemical substance that alters the rate of reaction and remains unchanged.

Inhibitor

A negative catalyst, slows down a reaction.

Catalyst Principle

Catalysts work by providing an alternative pathway for the reaction.

Effects of Increasing Factors

Increasing temperature, concentration, surface area, or adding a catalyst.

Rate Curve - Increased Factors

Steeper gradient and becomes horizontal sooner.

Effects of Decreasing Factors

Decreasing temperature, concentration, surface area, or adding an inhibitor.

Rate Curve - Decreased Factors

Shallower gradient and becomes horizontal later.

Activation Energy

The energy required to break the original bonds in the reactants.

Catalyst Mechanism

A catalyst lowers the activation energy required.

Effective collisions

Collisions that result in a reaction.

Light Intensity

As light intensity increases the rate of reaction increases.

Products

The concentration of the products increases during a reaction

Temperature and Kinetic Energy

If temperature of the reaction increases the reactant particles gain kinetic energy

Concentration of reactants

If the concentration of the reactants increases, the reactant particles per unit volume increases

Surface Area

The decrease in particle size, the greater the surface area exposed to the particles of the other reactant

Rate Curves

If a measured property is plotted against time, a rate curve is obtained.

Properties Plotted Against Time

Volume of gas produced, mass of reaction, concentration.

Catalyst or Inhibitor

They can either speed up a reaction – Catalyst or slow down a reaction – Inhibitor (negative catalyst)

Reaction Rate

The speed at which a chemical reaction occurs.