Chalter 19 Flashcards
What happens if ALL THE UNITS CANCEL DOWN FOR KC, what to say
will just say NO UNITS
How to do kc expression
Products to power. Of moles / reactants to power of moles
Calculating KC required what type of concentrations?
Must have the CONCENTRATIONS AT EQUILIBORUM SO MUST WORK THESE OTU FIRST
How to do KC expression for homogenous and heterogenous EQUILIBIRUM?
Homogenous = all species the same = do it as normal fine
Heterogenous = DIFFERENT STATES
I’m this case it’s assumed that the SOLID AND LIQUID species concs are ESSENTIALLY CONSTNAT
SO IGNORE THEM!
Again what to ignore heterogenous
MUSR IGNORE SOLID AND LIQUID AS CONCS ARE CONSTANT
How ti find moles at equiloborum?
HOW TO FIND CONC as that is what is needed for KC
Write down moles at start and everything you know
Work out the ratios of what must have reacted
ALWAYS SUBTRAVT SECOND ROW
Remmeber moles at the end DOESNT HAVE TO BE MOLES at start, moles dome have to be conserved
For KC, find con by dividing by TOTAL VOLUME, as it’s a mixture
= don’t make mistake of ignoring because they a,k have same divisor, that’s why there is squares!
How ti find cinc again kc
Divide moles at EQUILIBIRUM / total volume
How to use experimental titration to find KC
If using AQEUOUS CATALYST, and one of products is WATER, WHAT TODO
First only can do titration if some product is acid
Leave you reactants and allow them to come to equiliborum for one WEEK
Next do a titration to accustelth determine how many moles of acid they’re at equiloborum!
Remember if using a catalyst, do a control titration on it to spremember ti subtract these form total (acid moles)
2) OKAY if one of the products Is water and caltyst is AWEUOUS make sure to take this it is count in reactions
Remember once you have one changes you have all, left is subtravt, right is add
Now divide by total volume
How to check if a mixture is truly under equiloborum
After however long you gave to reach it, give another rvintirl the same time
If they end up getting the same concentrations, that means it’s likely they both went to EQUILBKRUM
Mole fraction. Partial pressure Kp
Kp is same thing but only when all things are gases
Here workmout mole fraction = mole / total moles and multiply by partial pressure
But if they give you PRESSURE AT EQUILIBIRUM can just use that straight as it’s proprtinsl to moles at room TEMPERTAURE
Remmebe to make ti curly brackets
Checks
Mole fractions should add to total moles
Partial pressures should add to toal pressure
Units for KP?
Don’t lack for KPa
Same way, but might have to cancel usign ATMA or KPA etc
For KPa, don’t make a capital 😭
What if it’s a HETEROGENOUS EQUATION, what to write down?
Must only use GASES, KP only for gases
It follows that any hetorhenous EQUILIBIRUM only use aqueous or gases
Again what is the only thing that will change K
Only thing that changes is it TEMP
Any conc pressure etc keeps it constsnt- that’s the whole Point
Cheat
how to determine if thr KP increases or decrease with an increase temp depending on if forward reavtion is endo or exo
To Remmeber =
If forward exo the equiloborum will shift ot the left
Thing about this, this will decrease top and increase the bottoms
Therefore KP DECREASES
But if forced endo and shifts there
The top increase and bottom decrease = KP INCREASES
But now we have to explain why the equiloborum shifts
Now that we know where kp goes, using kp , edp,ain why the equkibkrum shifts the direction ti does without le Chatellier
2) how ti say it in exam tehnciaue form)
Say you increase temp and Kp increases at higher temp
The kp expression is less than new kp, so must increase
This is aciheiged the FASTEST, when the top increase and bottom decreases
This literally causes a shift to the RIGHT , done explained
2) explain it by saying to math. The KP, products must increase and revstnstnrs decrease, therefore eaukibkrum shifts to the right.
How to prove le chestier shifts for when conc is increased at same temp
Say conc of products
Increasing the conc of the reactant wil, cause KC to lower in the reaction
But this must stay the same, so Kc must go up again
This is achieved by products increasing and reactants decreasing
As a result this causes an equilibrium shift to the RIGHT
How to predict equkibkrum shift for PRESSURE INCREASE
Increase TOTAL PRESSUEE will increase partial pressure of REAVTNAT AND GASES
This will change the KP depending on the powers
You need to reverse this so KP stays the same
- it follows that you’ll need to decrease the side with higher power and increase the side with lower to negate the change
Thus the equilibrium shifts accordingly
EQUILBKRUM predictions summary
Temoewrure
1) remember how to figure out what happens to KP with increase temo if forward exo endo
- now use the fact that it increases/ decreased to explain how change happens. If it increases, then you’ll have to increase top and decrease bottom, shift to the right etc
2) conc
# k stays the same so increasing conc of left side decreases k, needs to go up again so reactant decrease product increase shifts to right
3) pressure
# increasing pressure increases pressure for ALL
- must look out powers to Det one if kp increases or decreases
- then make adjustment
In each case determine what happens usign le chat.lied and then try to justify it
How do catalysts affect rate of reaction and k constsnt
Increases rate if reavtion
But has nothing to do with K CONSTANT AT ALL
rate for forwards and backward reactions are just achieved quicker
