Mod 5 EQUILIBRIUM AND ACID REACTIONS: Static and dynamic equilibrium Flashcards
Inquiry question: What happens when chemical reactions do not go through to completion?
True or false: Reversible reactions always reaches completion.
False. The reaction never reaches completion because the products can be re-formed into reactants
Describe the process in reversible reactions.
Forward reaction (reactants → products) happens at a fast rate at the beginning but eventually decreases and backward reaction (products → reactants) happens at a slow rate at the beginning but eventually increases (eventually their rates will reach equilibrium)
Describe the difference between static equilibrium and dynamic equilibrium
Static equilibrium only allows for reactants to convert to products, with the reactants being completely used up during the reaction, reaching completion.
Dynamic equilibrium allows for the reaction to occur vice versa when enough energy is present to stimulate particles colliding.
Identify open, closed, and isolated systems
Open system - both matter and energy leave the system
Closed system - matter is conserved, but energy can still be exchanged with the environment
Isolated system - insulated, both matter and energy are preserved
Write the equation for Gibbs Free Energy, identifying what each variable means (include units)
△G = △H - T△S
G - gibbs free energy (measured in J/kJ)
H - enthalpy (measured in J/kJ)
T - temperature (measured in Kelvin)
S - entropy (measured in J/K, joules per kelvin)
Identify what is Gibbs Free Energy
Gibbs free energy is the associated with a chemical reaction that can be used to do work.
What are the conditions for a chemical reaction to be considered _ _ _ - _ _ _ _ _ _ _ _ _ _ _, _ _ _ _ _ _ _ _ _ _ _, or at _ _ _ _ _ _ _ _ _ _ _, based on the value of the Gibbs free energy change (ΔG) respectibely?
△G > 0, _ _ _ - _ _ _ _ _ _ _ _ _ _ _ (endergonic, work energy is _ _ _ _ _ _ _ _)
△G < 0, _ _ _ _ _ _ _ _ _ _ _ (exergonic, work energy is _ _ _ _ _ _ _ _)
△G = 0, at _ _ _ _ _ _ _ _ _ _ _
△G > 0, [non-spontaneous] (work energy is released)
△G < 0, [spontaneous] (exergonic, work energy is absorbed)
△G = 0, at [equilibrium]
Would this reaction occur?
Scenario:
- Forward reaction is exothermic, with negative ∆S
→ driven by favourable enthalpy change (because exothermic means enthalpy change is negative) - Reverse reaction is therefore endothermic(the opposite of the forward reaction), positive ∆S
Yes, as it is driven by favourable entropy change (because we like when things are messy and disordered)
Would this reaction occur?
Scenario:
- Forward reaction is endothermic, positive ∆S
→ Driven by favourable entropy
- Reverse reaction is exothermic, negative ∆S
Yes, as it is driven by favourable enthalpy
How would this be thought of as:
(△H = -ve) is an energetically favourable reaction
Think of it as all reactions want to release energy rather than absorb it
How would this be thought as:
(△S = +ve) is an entropically favourable reaction
Think of it as you favour messy room over clean room because to clean your room you need to put energy into it
Would this reaction occur?
Scenario:
- Forward reaction is exothermic, positive ∆S
→ Drive by both favourable enthalpy and entropy - Reverse reaction is therefore endothermic, negative ∆S
Reaction will not occur as there is nothing that drives it
What are the characteristics of irreversible, non-equilibrium reactions? (Hint: change in enthalpy and entropy)
Irreversible, non-equilibrium reactions have a forward reaction that favors both a change in enthalpy and entropy (∆H < 0 and ∆S > 0). Consequently, their reversion reaction is always non-spontaneous due to both an unfavorable change in enthalpy and entropy (∆H > 0 and ∆S < 0). The Gibbs free energy of these reactions is negative at all temperatures, indicating that they are always spontaneous; thus, the reverse reaction is always nonspontaneous
Fill in the blanks:
In an open system, combustion reactions are always _ _ _ _ _ _ _ _ _ _ _ _ because carbon dioxide and water leave the system.
In a closed system, combustion reactions are _ _ _ _ _ _ _ _ _ _ _ _ because carbon dioxide and water do not _ _ _ _ _ due to the reaction having a _ _ _ _ _ _ _ _ change in ∆G at all temperatures
irreversible, irreversible, react, positive
Why is it crucial to convert entropy from joules per kelvin per mole (J/K/mol) to kilojoules per kelvin per mole (kJ/K/mol) for accurate calculations?
Converting entropy units from joules to kilojoules ensures consistency in units throughout the calculation process, preventing errors and maintaining accuracy.
Fill in the blank:
Photosynthesis requires a lot of light energy (∆H > 0), there is also a _ _ _ _ _ _ _ _ in entropy because the final product produced is a large solid _ _ _ _ _ _ _ molecule (∆S < 0). For this reason, the reaction is _ _ _ - _ _ _ _ _ _ _ _ _ _ _. Theoretically, it wouldn’t occur but a biological _ _ _ _ _ _ _ _ (enzyme that is chlorophyll) initiates this reaction. The _ _ _ _ _ _ _ reaction of photosynthesis does not take place because the activation energy is too _ _ _ _ in the absence of a suitable catalyst. It only occurs in an _ _ _ _ system which means that matter leaves the system and isn’t retrieved back (e.g O2 leaves the system through stomata, pores in leaves).
decrease, glucose, nonspontaneous, catalyst, reverse, high, open
State the three rules of collision theory
The particles must:
1. Collide
2. Collide with sufficient kinetic energy (minimum is activation energy)
3. Collide with correct orientation
Identify and describe the factors that affect collision rate
Concentration:
- An increased concentration means increased likelihood of successful collisions, increasing reaction rate.
- Decreased concentration means fewer particles that collides, meaning the likelihood of successful collisions happening is small, decreasing reaction rate
Pressure:
- Increased pressure = decreased volume (inversely proportionate to each other).
Meaning that the atoms have higher potential to collide, increasing reaction rate.
- Decreased pressure = increased volume
Less possibility of colliding as particles have more potential positions they could occupy, decreasing reaction rate
Temperature
- Increased temperature increases kinetic energy of particles which speeds the collision rate, increasing reaction rate
- Decreased temperature decreases kinetic energy that slows down particle collision, decreasing reaction rate
Define catalyst
A substance that speeds up the reaction rate by lowering activation energy.
True or false: Catalysts do not shift the position of equilibrium
True, because catalysts only speeds up the rate of a forward and reverse reaction to the same extent. This does not alternate the position of equilibrium whatsoever
