Intro to Kinetics

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Intro to Kinetics
2011-04-27 10:02:45
Reaction rates potential energy diagrams

Review of terms for NYS Regents Chemistry Unit on Kinetics
Show Answers:

  1. State the two conditions of molecules for a collision to be effective
    Molecules must collide with the proper orientation and speed (energy)
  2. Define Activation Energy
    Activation Energy is the minimum amt of energy substances must have for a reaction to occur
  3. According to Ref J, will this reaction occur? Explain
    Zn (s) + MgCl2 (aq)
    No Zinc is less active than Mg and can not replace it
  4. Explain which substances will react:
    NaCl(s) with AgNO3(s)
    or HCl(aq) with NaOH(aq)
    The aqueous solutions will react, not the solid reactants, due to the free moving particles in a solution.
  5. Which type of substance reacts faster, ionic cmpds or covalent?
    Ionic substances react faster than covalent.
  6. In terms of collision theory, why does an increase in temperature inc the rate of a rxn?
    An inc in temp speeds up the molecules thus inc the number of collisions. The result is an inc in the rate of the rxn.
  7. In terms of energy, why does addition of a catalyst speed up a rxn?
    A catalyst lowers the activation energy and so inc the rate of the reaction.
  8. Explain why pressure only affects gases.
    Gases can be affected by pressure because thier molecules are so far apart unlike a solid or liquid whose particles are close together.
  9. Define activated complex
    The activated complex is a short-lived substance that must be formed in order for a reaction to occur.
  10. Define endothermic
    Endothermic reaction has a net gain of heat. Energy is a reactant.
  11. Define Exothermic
    Exothermic is a net loss of heat. Energy is a product.
  12. How is ∆ H calculated?
    ∆ H = energy of products - energy of reactants
  13. What is enthalpy?
    Enthalpy is the change in heat of a rxn or ∆ H
  14. State the units in which heat and temperature are measured
    Heat is measured in Joules and temperature is measured in celsius or kelvin.
  15. Of what is temperature a measure?
    Temperature is a measure of kinetic energy.

  16. Is this rxn exothermic or endothermic?
    Rxn is endothermic

  17. Label A, B, and C
    • A is the Activation Energy of the forward rxn, B is A. E. of reverse, and C is change in heat.
  18. For any reversible reaction, Compare the ∆ H of the forward with the ∆ H of the reverse.
    The ∆ H of the forward reaction is always equal to the ∆ H of the reverse.
  19. On a potential energy diagram, what values can a catalyst not change.
    • A catlyst does not change the value of
    • ∆ H, the reactants or the products.
  20. Compare the value of the reactants and products in an exothermic rxn.
    The products are at a lower potential energy than the reactants in an exothermic rxn.