Thermochemistry
What basic role do catalysts play in chemical reactions according to their representation on an Energy Diagram?
They increase temperatures at which reactions take place
However they lower overall yields from given processes
They reduce activation energies needed for reactions making them quicker
Airborne agents speed-up breaking bonds amongst substrates only
Which of the following descriptions best characterizes the following reaction: H₂O (g) -> H₂O (l)?
activation energy will be negative
activation energy is 0
the end point will be higher than the starting point
the end point will be lower the the starting point
How does an increase in temperature generally affect the rate of a chemical reaction as depicted on an energy diagram?
It increases the number of molecules that can overcome the activation energy barrier.
It decreases the overall enthalpy change of the reactants and products.
It lowers the activation energy necessary for reactants to form products.
It changes an endothermic reaction into an exothermic one.
Considering the periodic trends, which element would likely have the highest ionization energy?
Nitrogen (N)
Helium (He)
Oxygen (O)
Fluorine (F)
In an energy profile for a reaction with both endothermic and exothermic steps, which step is displayed by the lowest point on a diagram?
Initial reactants in their ground state
Formation of final products with released heat
Intermediate compounds in exothermic transition phase
Transition state leading to endothermic step
When comparing atoms from Group I elements as they descend down their group, which one is expected to have the smallest second ionization energy?
Lithium (Li)
Sodium (Na)
Potassium (K)
Cesium (Cs)
If the final energy level on an energy diagram is lower than the initial energy level, this indicates that the reaction is ___.
cannot be determined
always undergoes change of state from gas to solid (deposition)
exothermic
endothermic

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What role does a catalyst play in modifying an enzyme-catalyzed biological reactions’ energy diagram?
It raises the initial energy of reactants
It changes the overall enthalpy change of the reaction.
It lowers the activation energy without altering the overall enthalpy change.
It decreases the final energy of products
Which factor would most likely increase the activation energy required for a chemical reaction to proceed?
Addition of a catalyst.
Higher concentration of reactants.
Increased temperature of the system.
Stronger bonding in the reactants.
In an exothermic reaction's potential energy diagram, what does it mean if there is significant distance between energies of reactants and products?
Reactant stability exceeds product stability and absorbs more heat from surroundings.
Products are less stable than reactants and require more inputted heat.
There is substantial release of energy from reactants turning into products.
Activation energies exceed total transferred energies impacting conservation laws.