Kinetics and equilibrium Flashcards
(46 cards)
What is meant by the term activation energy
The minimum energy needed for a succesful reaction to occur or a succesful collision to occur
Why at a fixed temp does the rate of a reaction double when the conc doubles
As there are now twice the number of particles in a given volume so twice the number of collisions/ higher collision frequency
Why is it possible to use a simplified formula as a measure of the rate of reaction
As it is a fixed value there is a fixed endpoint
Give one reason why the reaction between hydrogen and chlorine is very slow at rtp
As not many particles have enough energy to react (Ea)
Explain why a small increase in temp can lead to a large increase in ror between h and cl
As MANY momre particles have an energy in excess of Ea so higher succesful collisions
Explain effect of increasing conc on..
More FREQUENT succesful collisions
Explain when equilibrium is reached
When the concentrations are CONSTANT not the same bc their different its when they are constant and level off
Use le chateliers principle to state whether a …
High as fwd reac is so using a higher temp = favour the forward reac, producing a higher yield of hydrogen at high temps the equilibrium shifts to the right to oppose the increase in temp.
Why is high operating pressure used in industry
As the reaction gets to equilibrium faster so more particles in a given vol so increased collision frequency
Explain why the catalyst is more effective when coated onto an unreactive honeycomb
As there is a bigger surface area so more effective collisions
Will there be any chance of yield if there are the same number of moles on both side with pressure
No make sure you check
State the effect if any on the value of kc of adding more hydrogen to the equilibrium mixture
No effect- only temp changes kc not conc or whatever.
Define enthalpy change
The heat or energy change at constant pressure
Define hess’ law
The enthalpy change is independent of the route taken
Define the standard enthalpy change of formation
The enthalpy change at constant pressure when 1 mole of a compound is formed from its constituent elements with all the reactants and products in their standard states.
Why can a value of something not be zero
As it is not in its standard state
Why is the standard enthalpy of formation of barium and aluminium both zero
As they are both elements
Why can an experiment have a much smaller experimental error
Due to a lower heat loss
Define the term standard enthalpy of combustion
The enthalpy change when 1 mol of a compound is completely burnt in oxygen under standard conditions
Define rate of reaction
The of change of concentration of a substance in a given unit of time
If they ask you what is happening to w if its a straight line
The rate is zero as all the… eg mg has reacted or been used up
If your working out the moles using the q/n thing what do i need to remember
If you have the q firstly make sure convert into kj. And if they give you a neutralisation value eg -51kj make it positive and do the kj/51
If they want you to find out the minimum conc of something mo/vo
So do the moles divided by v make sure you divide by 1000 in dm3
Suggest one possible risk to a person who uses a hand warmer containing sodium hydroxide and hcl
The container can split releasing corrosive chemicals, can burn hands
