Chemistry: 14 T

In general, for a reaction rate to double, a rise in temperature of how many degrees Celsius is required?

10°C

Spontaneous reactions always occur rapidly.

False. Even though a specific reaction may be spontaneous, it will not proceed rapidly unless the initial energy barrier is overcome.

A thermodynamically favorable reaction proceeds spontaneously.

False. Some thermodynamically favorable reactions proceed at an extremely slow rate, others are rapid, others need an energetic push to get started, and still others proceed on their own.

Doubling the concentration of a reactant always causes the reaction rate to double.

False. The concentration of a reactant is always directly proportional to the reaction rate. For hydrogen gas, doubling the concentration doubles the reaction rate; other rates of a reaction are affected by their specific reactant's concentration.

A reaction that has a high activation energy is more likely to occur than a reaction with a low activation energy.

False. The lower the activation energy, the faster the reaction will occur because the activation energy is the minimum amount of kinetic energy that must be possessed by the colliding molecules before they can react.

The rate law for the reaction 4HBr (g) + O₂ (g) → 2H₂O (g) + 2Br₂ (g) is this: rate = k[O2][HBr]. What will happen to the reaction rate if the HBr concentration is tripled?

It will increase ninefold.

If a reaction is second order in a particular reactant, how would tripling the concentration of that reactant affect the rate of the reaction?

The rate would increase ninefold.

The elementary step that is the fastest of a reaction mechanism and therefore limits how fast the reaction will occur is called the rate-determining step.

The rate-determining step is the slowest step of a reaction mechanism.

A rate law with a specific rate constant allows you to calculate how fast a reaction will occur.

True

An inhibitor is used to reduce a catalyst's undesirable effects, such as the spoiling of food.

True

A catalyst does not affect the concentration of products formed in a reaction; it affects only the rate at which they are produced.

True.

Any factor that increases the number of effective collisions increases the reaction rate.

True.

a theoretical, unstable, high-energy, transitional substance in a reaction

activated complex

the minimum amount of kinetic energy that must be possessed by reactants before they can react

activation energy

The process of molecules of one substance collecting on the surface of another is called

adsorption.

Any substance that changes a reaction rate without being permanently changed or consumed is called a(n)

catalyst.

explains why reactions occur at greater or slower rates, depending on reaction conditions

collision theory

What do the square brackets around reactants in a rate law formula represent?

concentration

According to the collision theory, what two conditions must be met in order to have a reaction between colliding molecules?

enough force and proper orientation

Which of the following is a special and distinct class of catalysts composed of naturally occurring biological substances?

enzyme

Rate laws are determined

experimentally.

An energy diagram that is higher on the right side (end) than on the left side (start)

has a positive DH and is endothermic.

Solid materials that are capable of adsorbing molecules of gases or liquids onto their surfaces are called __________ catalysts.

heterogeneous

In a(n) __________ reaction, the reactants exist in two different phases.

heterogeneous.

In a(n) __________ reaction, all the reactants and products are in the same phase or state of matter.

homogeneous

Substances formed in one step of a complex reaction and consumed in the next step are called

intermediates.

the study of the rates of reactions and the steps by which they occur

kinetics

What is the term for the study of how the human body processes medication?

pharmokinetics

an equation that mathematically describes how fast a reaction can occur

rate law

the series of steps that make up a reaction

reaction mechanism

indicates how the rate of a reaction is affected by a specific reactant's concentration

reaction order

usually tells how fast reactants change into products, using units describing the change in concentrations such as molarity per second or moles per second

reaction rate

What potentially dangerous type of chemical reaction can occur if reaction rates are not controlled?

spontaneous combustion