Questions and Answers
Which pairs of variables are directly proportional?
Which phase changes are classified as endothermic?
Which of the following reactions are endothermic?
An exothermic reaction is always negative.
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Which chemical changes are classified as exothermic?
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What factors determine whether a collision between two reactant molecules will result in a reaction?
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Which factors will decrease the number of collisions that result in a chemical reaction?
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What would increase the number of collisions in the reaction A + B ⟶ C?
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Name some factors that might influence the rate of a chemical reaction.
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Which of the following factors will not increase the rate of the reaction A + B ⟶ AB?
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What is the order of the reaction when 2NO(g) + O2(g) ⟶ 2NO2(g)?
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Study Notes
Proportional Relationships in Chemistry
- Pressure (P) and Temperature (T), Temperature (T) and Volume (V), Pressure (P) and moles (n), and Volume (V) and moles (n) are directly proportional.
- Pressure (P) and Volume (V) are inversely proportional.
Phase Changes Classification
-
Endothermic Processes:
- Solid to liquid (melting)
- Liquid to gas (vaporization)
- Solid to gas (sublimation)
-
Exothermic Processes:
- Gas to liquid (condensation)
- Liquid to solid (freezing)
- Gas to solid (deposition)
Reaction Classification
-
Endothermic Reactions:
- Microwave popcorn popping
- Boiling water
-
Exothermic Reactions:
- Burning a match
- Burning rocket fuel
- Chemical reaction in heat packs
Identifying Exothermic Reactions
- Exothermic reactions always have a negative change in enthalpy (-ΔH).
Chemical Changes Classification
-
Endothermic Changes:
- Chemical reactions that feel cold to the touch, like in cold packs used for injuries.
-
Exothermic Changes:
- Reactions like burning wood or using pocket hand warmers that feel hot upon reaction.
Collision Factors for Reactions
- Correct orientation during particle collisions is necessary.
- Sufficient collision energy is needed to exceed activation energy.
Factors Reducing Reaction Collisions
- Increasing the volume of the reaction vessel leads to fewer collisions.
- Lowering temperature reduces kinetic energy of particles.
- Decreasing reactant concentration results in fewer collisions.
Collision Likelihood in Reactions (A+B⟶C)
-
Increases collisions:
- Raising reaction temperature
- Increasing concentration of reactant B
-
No effect:
- Lowering activation energy
-
Decreases collisions:
- Lowering temperature
- Decreasing concentration of reactants
Influencing Chemical Reaction Rates
- Factors that increase reaction rates include:
- Adding a catalyst
- Changing the temperature
- Altering the concentration of reactants
- Modifying reactant surface area
- Nature of the reactants
Reaction Rate Influences (A+B⟶AB)
- Factors that do not increase the rate of reaction:
- Increasing concentration of product AB
- Decreasing kinetic energy of molecules
Reaction Kinetics of Nitric Oxide and Oxygen
- Reaction: 2NO(g) + O2(g) ⟶ 2NO2(g)
- Doubling the concentration of oxygen doubles the reaction rate.
- Doubling concentrations of both reactants increases the reaction rate by a factor of eight.
- The reaction is first-order in oxygen and second-order in nitric oxide.
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Description
Prepare for your chemistry exam with these handy flashcards covering key concepts. You'll review direct and inverse proportionalities, phase changes, and the classification of reactions. Perfect for quick revisions before the test!
