Unit 1 - Section 6 Flashcards
What is Le Chatelier’s principle?
If a reaction at equilibrium is subject to a change in concentration, pressure or temperature, the position of equilibrium will move to counteract the change
What would be the effect on the equilibrium reaction of 2SO2 + O2 2SO3 (Delta)H = -197 kJ mol -1 If: 1) the pressure increase 2) the temperature increase
1) if the pressure increase then, because there are 3 moles on the left and 2 on the right, the reaction would go to the right
2) if temperature increased then, because the forwards reaction is exothermic (a negative (delta)H ), the equation would shift to the left to cool it down
How do you work out the equilibrium constant? (Kc)
aA + bB dD + eE
[D]^d [E]^e
—————-
[A]^a [B]^b
Where A,B,C and D are concentrations
How do you find out the units for Kc?
Because all the concentrations are in moldm^-3 then you must cancel them out with what’s on bottom
If the only moldm^-3 is on he bottom change it to mol^-1 dm^3
How does changing the temperature effect the Kc?
The reaction will change to either cool or heat the reaction ( depending on what way the (delta)H is) so the concentration of that side of the equation will increase, changing the Kc
What effect would changing the concentration of the reaction do to the Kc?
Nothing as the reaction will react to change this back to the normal Kc
What effect would adding a catalyst have on the Kc?
Adding a catalyst would have no effect on the position of equilibrium and therefore no effect on the Kc
What is oxidation?
A loss of electrons
What is reduction?
A gain of electrons
What is a redox reaction?
When something is oxidised in a reaction but something else is reduced
What is an oxidation state?
It tells you how many electrons the element has donated or accepted
What are the rules of oxidation states?
1) elements on there own have an oxidation state of 0
2) elements bonded to the same element has an oxidation state of 0
3) oxygens oxidation states in a compound is almost always -2
4) if hydrogen is bonded it will have a +1 charge unless bonded to a metal wear it would be a +1 charge
How do you write a half equation?
Write the element and how that elements charge has changed (eg if it has become negative it would add electrons to it and if it has become positive then it would have lost electrons)