Topic 10 Flashcards
Is this reaction reversible or not and why?
H_2 + O => H_2O
There is very little reactants left over so its irriversable
How do you determine if a reaction is reversable?
- Depends on the concentrations of Reactants and Products
- Even if the reaction goes to 99% completion there is a small reverse reaction occurring but if over 99% consider it a completed reaction
What is equilibrium and how is it attained?
Where the concentrations of reacts and products do not change in a closed system
- The rate of the forward reaction decreases over time
- The rate of the backward reaction increases
- Where eventually the rates of the forward reaction and backward reaction become equal
What is Dynamic Equilibrium?
Where the forward and backward reaction rates are equal and are happening at the same rate
How is dynamic equilibrium attained and what are the conditions?
Conditions
- Reversible reaction
- Closed system
How dynamic equilibrium is attained
- Simultaneous forward and backward reactions
- Forward rate = Backwards rate
- Concentrations of reactants + products constant (don’t change)
What happens to position of equilibrium when you increase concentration?
- Increase concentration of reactants
- Rate of forward increases
- More product forms + product concentration increases
- Equilibrium moved to the right (more product compared to original amount)
How can pressure be changed and how does it effect position of equilibrium?
- The reaction must be gaseous
- Pressure can increase by decreasing volume (Visa versa)
- Pressure of gaseous mixture = no of gas molecules in a given volume
- Using more moles of the reactants in the same volume (Visa versa)
Pressure shifts to the position with fewer moles of gas
What overall effect does increasing temperature have on both products and reactants?
- Both forward and backward reactions increase
- Rate of Endothermic reaction will have a greater increase(more heat available to be taken in)
- Rate of Exothermic reaction will have a lower increase
Is this reaction exothermic or endothermic
The enthalpy change is positive so its endothermic
Enthalpy of Products are higher than that of the reactant
Is this reaction exothermic or endothermic
The enthalpy change is negative so its exothermic
Enthalpy of Reactants are higher than that of the products
What is the effect of a catalyst on the position of equilibrium?
- Decreases activation energy for both reactions
- So rate of both reactions are increased
- Position of equilibrium is not effected
What are the conditions of the Haber Process and why aren’t they different?
- Reaction between Nitrogen and Hydrogen is extremely slow because the NN triple bond
- This activation energy is high so an iron catalyst is used
- This needs a low temperature so be effective BUT a TOO LOW means the rate of reaction is too slow
- So 450 is used as a compromise
- A pressure would be needed to match the 450 temp
- 100atm = 12-13% (Too low to be productive - Slows rate of reaction)
- 400atm = 27 -28% (Too high to be economical)
- 250atm is the compromise
What is the formula Kc and what does it show?
Kc is the equilibrium constant where
If 1 > Kc then the reaction favours the left hand side
If 1 < Kc then the reaction favours the right hand side
How do you work out Kc with concentrations and volume?
How do you work out Kc using concentration and NO Volume?
