CHEM 155 Lecture 4: Chemical Kinetics in Physical Chemistry
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Questions and Answers

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?

    <p>The total number of molecules involved in the reaction</p> Signup and view all the answers

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

    <p>Volume</p> Signup and view all the answers

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

    <p>The relationship between reactant concentrations and reaction rate</p> Signup and view all the answers

    What is the molecularity of an elementary reaction defined as?

    <p>The number of reactant molecules involved in a reaction</p> Signup and view all the answers

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

    <p>The slowest step</p> Signup and view all the answers

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

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

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

    <p>It becomes a reactant for another elementary reaction</p> Signup and view all the answers

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

    <p>Many paths leading to different products</p> Signup and view all the answers

    What determines the speed at which a reaction can proceed?

    <p>The slowest step in the mechanism</p> 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?

    <p>Chemical equilibrium</p> Signup and view all the answers

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

    <p>Rate is constant and independent of the concentration</p> 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?

    <p>Reversible reactions</p> Signup and view all the answers

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

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

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

    <p>Remains constant at all concentrations</p> Signup and view all the answers

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

    <p>Molecularity and order are equal</p> Signup and view all the answers

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

    <p>Proper orientation and sufficient kinetic energy of colliding molecules</p> Signup and view all the answers

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

    <p>Energy from the kinetic energy of reacting molecules before collision</p> Signup and view all the answers

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

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

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

    <p>Transition state theory</p> Signup and view all the answers

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

    <p>Rate constant (k)</p> Signup and view all the answers

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

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

    What is formed during a collision between reactant molecules?

    <p>Transition state</p> Signup and view all the answers

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

    <p>Slow down due to electron cloud repulsion</p> Signup and view all the answers

    What is the activated complex also known as?

    <p>Transition state</p> Signup and view all the answers

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

    <p>Weakens</p> 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?

    <p>Endothermic</p> Signup and view all the answers

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

    <p>Activation energy</p> Signup and view all the answers

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