Chalter 19

Question 1

What happens if ALL THE UNITS CANCEL DOWN FOR KC, what to say

Answer 1

will just say NO UNITS

Question 2

How to do kc expression

Answer 2

Products to power. Of moles / reactants to power of moles

Question 3

Calculating KC required what type of concentrations?

Answer 3

Must have the CONCENTRATIONS AT EQUILIBORUM SO MUST WORK THESE OTU FIRST

Question 4

How to do KC expression for homogenous and heterogenous EQUILIBIRUM?

Answer 4

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!

Question 5

Again what to ignore heterogenous

Answer 5

MUSR IGNORE SOLID AND LIQUID AS CONCS ARE CONSTANT

Question 6

How ti find moles at equiloborum?

HOW TO FIND CONC as that is what is needed for KC

Answer 6

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!

Question 7

How ti find cinc again kc

Answer 7

Divide moles at EQUILIBIRUM / total volume

Question 8

How to use experimental titration to find KC

If using AQEUOUS CATALYST, and one of products is WATER, WHAT TODO

Answer 8

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

Question 9

How to check if a mixture is truly under equiloborum

Answer 9

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

Question 10

Mole fraction. Partial pressure Kp

Answer 10

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

Question 11

Checks

Answer 11

Mole fractions should add to total moles

Partial pressures should add to toal pressure

Question 12

Units for KP?

Don’t lack for KPa

Answer 12

Same way, but might have to cancel usign ATMA or KPA etc

For KPa, don’t make a capital 😭

Question 13

What if it’s a HETEROGENOUS EQUATION, what to write down?

Answer 13

Must only use GASES, KP only for gases

It follows that any hetorhenous EQUILIBIRUM only use aqueous or gases

Question 14

Again what is the only thing that will change K

Answer 14

Only thing that changes is it TEMP
Any conc pressure etc keeps it constsnt- that’s the whole Point

Question 15

Cheat
how to determine if thr KP increases or decrease with an increase temp depending on if forward reavtion is endo or exo

Answer 15

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

Question 16

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)

Answer 16

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.

Question 17

How to prove le chestier shifts for when conc is increased at same temp

Say conc of products

Answer 17

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

Question 18

How to predict equkibkrum shift for PRESSURE INCREASE

Answer 18

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

Question 19

EQUILBKRUM predictions summary

Answer 19

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

Question 20

How do catalysts affect rate of reaction and k constsnt

Answer 20

Increases rate if reavtion

But has nothing to do with K CONSTANT AT ALL

rate for forwards and backward reactions are just achieved quicker