CHEM 155 Lecture 4: Chemical Kinetics in Physical Chemistry

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What is the branch of physical chemistry that deals with the rate of reactions?

Chemical Kinetics (correct)

Chemical Equilibrium

Thermodynamics

Quantum Mechanics

Why are average rates sometimes not useful in chemical kinetics?

They are too complex to calculate accurately

They do not consider the factors influencing reaction rates

They only focus on the beginning of a reaction

They cover a large time interval where the reaction rate changes significantly (correct)

What is an elementary reaction in chemistry?

A reaction influenced by catalysts

A reaction that occurs in multiple steps

A simple reaction that happens in a single step (correct)

A reaction that involves high temperatures

What does the term 'molecularity' refer to in chemical kinetics?

The total number of molecules involved in the reaction Signup and view all the answers

Which factor does not influence the rate of a reaction according to chemical kinetics?

Volume Signup and view all the answers

What aspect of a reaction does the order of reaction in chemical kinetics describe?

The relationship between reactant concentrations and reaction rate Signup and view all the answers

What is the molecularity of an elementary reaction defined as?

The number of reactant molecules involved in a reaction Signup and view all the answers

Which step in a reaction is usually considered the rate-determining step?

The slowest step Signup and view all the answers

Can the molecularity of a complex reaction be determined by looking at the overall reaction?

No, it is impossible to determine from the overall reaction Signup and view all the answers

In consecutive reactions, what role does the product formed in one elementary reaction play?

It becomes a reactant for another elementary reaction Signup and view all the answers

In parallel or side reactions, how many paths do the reacting substances typically follow?

Many paths leading to different products Signup and view all the answers

What determines the speed at which a reaction can proceed?

The slowest step in the mechanism Signup and view all the answers

What is the term used to describe the situation when the rate of the forward reaction equals the rate of the backward reaction?

Chemical equilibrium Signup and view all the answers

In a zero order reaction, what is the relationship between the rate and the concentration of reactants?

Rate is constant and independent of the concentration Signup and view all the answers

What is the term used to describe reactions where the products formed also react to give back the reactants?

Reversible reactions Signup and view all the answers

What is the significance of the half-life of a reaction?

It shows how long it takes for half of the reaction to be completed Signup and view all the answers

For a first order reaction, what is true about its half-life?

Remains constant at all concentrations Signup and view all the answers

What can be said about the molecularity and order in an elementary reaction?

Molecularity and order are equal Signup and view all the answers

What is required for a chemical reaction to take place according to the collision theory?

Proper orientation and sufficient kinetic energy of colliding molecules Signup and view all the answers

Where does the energy for bond breaking in a chemical reaction come from?

Energy from the kinetic energy of reacting molecules before collision Signup and view all the answers

What is the correct orientation of colliding molecules for a successful reaction?

Orientation that ensures direct contact between atoms involved in bond breaking and forming Signup and view all the answers

Which theory assumes that simply a collision between reactant molecules does not cause a reaction?

Transition state theory Signup and view all the answers

What does the rate of a chemical reaction depend on according to the text?

Rate constant (k) Signup and view all the answers

What is the role of activation energy in the Arrhenius equation?

To speed up the reaction by providing a threshold energy barrier Signup and view all the answers

What is formed during a collision between reactant molecules?

Transition state Signup and view all the answers

What happens to the fast approaching reactant molecules during a collision?

Slow down due to electron cloud repulsion Signup and view all the answers

What is the activated complex also known as?

Transition state Signup and view all the answers

What happens to the B-C bond when a partial bond forms between atoms A and B?

Weakens Signup and view all the answers

If the potential energy of the products is greater than that of the reactants, what can be said about the reaction?

Endothermic Signup and view all the answers

What is the difference in potential energy between the reactants and the activated complex called?

Activation energy Signup and view all the answers