7.2.5

Change in conditions	Nature of the reaction at equilibrium	Effect on Kc	Effect on equilibrium to keep the Kc constant	Notes
Use in Haber Decreasing the pressure of a gaseous reaction	Increase in volume/pressure, when reactants react into product.	Decrease	Shift to the right to favour the product	You are changing the condition to go against the nature of the reaction at equilibrium so fewer products is produce and Kc decrease. The system then balances this out by shifting the equilibrium to the right to produce more products. This one is use in Haber process.
Use in Contact Increasing the pressure of a gaseous reaction	Decrease in volume/pressure, when reactants react into product.	Decrease	Shift to the right to favour the product	You are changing the condition to go against the nature of the reaction at equilibrium so fewer products is produce and Kc decrease. The system then balances this out by shifting the equilibrium to the right to produce more products. This one is use in Contact process.
Use in both Decreasing the temperature of an exothermic reaction	Exothermic when reactants react into product	Decrease	Shift to the right to favour the product	You are changing the condition to go against the nature of the reaction at equilibrium so fewer products is produce and Kc decrease. The system then balances this out by shifting the equilibrium to the right to produce more products. This one is use in Contact/Haber process.
Use in both Adding a catalyst	Doesn’t matter	No effect	No effect	Adding catalyst will increase the rate of reaction but make no effect to the equilibrium. However, both Contact/Haber process use catalyst since they lower the pressure so the collision frequency, KE of particle(less than Ea) and rate of reaction decrease. So they use catalyst to compensate.

7.2.4

A catalyst do not affect the eqiulibrium. It just increase and make the rate of reaction faster so equilibrium is reach faster.
Linking topic6-7
Increasing rate of reaction will make the reaction reach the equilibrium/"end point"/plateau in the graph faster (decreasing the rate will make it reach slower). But changing the rate do not affect the equilibrium and shifting the equilibrium do not affect the rate.

7.2.3 Apply Le Chatelier's principle to predict the effect on the value of Kc if pressure or volume or concentration is changed

Le Chatelier's Principle
At equilibrium the Kc of the reaction will remain constant. So if the product is remove, the reactant will react to qiuckly replace those product to keep the Kc constant, we say the eqiulibrium shift to the right to favor more prodcut. Similarly, if we add more reactant, they will qiuckly react to produce more product to keep the Kc constant, eqiulibrium shift to the right. From this this we conclude that, if the system, at eqiulibrium, experienced a change, the eqiulibrium will shift to minimize the effect of those change.

Change in conditions	Nature of the reaction at equilibrium	Effect on Kc	Effect on equilibrium to keep the Kc constant	Notes
Increase concentration of reactants	Constant concentration of  reactant/product	Decrease	Shift to the right to favour the product	You are putting in more reactants and decreasing the Kc so the system balances this out by shifting the equilibrium to the right to produce more products.
Removing the products after they have been formed	Constant concentration of  reactant/product	Decrease	Shift to the right to favour the product	You are putting in more reactants and decreasing the Kc so the system balances this out by shifting the equilibrium to the right to produce more products.
Increasing the pressure of a gaseous reaction	Increase in volume/pressure, when reactants react into product.	Increases	Shift to the left to favour the reactant	You are changing the condition to favour the nature of the reaction at equilibrium so more product is produce and Kc increase. The system then balances this out by shifting the equilibrium to the left to get more reactants.
Decreasing the pressure of a gaseous reaction	Decrease in volume/pressure, when reactants react into product.	Increases	Shift to the left to favour the reactant	You are changing the condition to favour the nature of the reaction at equilibrium so more product is produce and Kc increase. The system then balances this out by shifting the equilibrium to the left to get more reactants.
Decreasing the temperature of an endothermic reaction	Endothermic when reactants react into product.	Increase	Shift to the left to favour the reactant	You are changing the condition to favour the nature of the reaction at equilibrium so more product is produce and Kc increase. The system then balances this out by shifting the equilibrium to the left to get more reactants.
Increasing the temperature of an exothermic reaction	Exothermic when reactants react into product	Increase	Shift to the left to favour the reactant	You are changing the condition to favour the nature of the reaction at equilibrium so more product is produce and Kc increase. The system then balances this out by shifting the equilibrium to the left to get more reactants.
Decreasing the pressure of a gaseous reaction	Increase in volume/pressure, when reactants react into product.	Decrease	Shift to the right to favour the product	You are changing the condition to go against the nature of the reaction at equilibrium so fewer products is produce and Kc decrease. The system then balances this out by shifting the equilibrium to the right to produce more products. This one is use in Haber process.
Increasing the pressure of a gaseous reaction	Decrease in volume/pressure, when reactants react into product.	Decrease	Shift to the right to favour the product	You are changing the condition to go against the nature of the reaction at equilibrium so fewer products is produce and Kc decrease. The system then balances this out by shifting the equilibrium to the right to produce more products. This one is use in Contact process.
Decreasing the temperature of an exothermic reaction	Exothermic when reactants react into product	Decrease	Shift to the right to favour the product	You are changing the condition to go against the nature of the reaction at equilibrium so fewer products is produce and Kc decrease. The system then balances this out by shifting the equilibrium to the right to produce more products. This one is use in Contact/Haber process.
Adding a catalyst	Doesn’t matter	No effect	No effect	Adding catalyst will increase the rate of reaction but make no effect to the equilibrium. However, both Contact/Haber process use catalyst since they lower the pressure so the collision frequency, KE of particle(less than Ea) and rate of reaction decrease. So they use catalyst to compensate.

Note- If Kc increase the equilibrium will shift to the left to balance it out. If Kc decrease then the equilibrium will shift to the right to balacne it out.

7.2.2 The extent of a reaction from the magnitude of Kc

1.       What does the word magnitude mean?

Magnitude means size. It’s how big something is. Ignore the direction and the positive or negative sign.

2.       Explain why the three reactions above do not have units for Kc

Because the amount of term on the numerator and denominator cancel out, there are same amount of terms so the unit cancel out. It can also be said the amount of moles of reactant is equal to the amount of mole of the product.

3. Deduce the extent of the reaction if Kc is

a. significantly larger than 1

This means that there is lots of product being produce in comparison to the reactant. The numerator (concentration of product) is significantly bigger than the denominator (concentration of reactant). The number of moles of product is bigger than the number of moles of the reactant. So the reaction goes nearly to completion. At equilibrium.

b. between 0.01 and 100

This means that there is amount the same significant concentration product and reactant presented at equilibrium. The concentration of product (numerator) is about the same as the concentration of reactant (denominator). The amount of moles of product is about the same as the number of mole of reactant.

c. extremely small

This means that the reaction barely proceeds. At equilibrium, there is significantly more concentration of reactant compare to the concentration of the product. The amount of moles of reactant is bigger than the amount of moles of product.

7.2.1 Equalibrium constant Kc

'7.2.1 I can deduce the equilibrium constant K_c for homogenous reactions'

a. What can change the value of Kc

Only temperature can change the value of Kc

b. The reaction must be at ____________ for the value of Kc to be calculated

The reaction must be at equilibrium for the value of Kc to be calculated

c. Define the term homogeneous

A homogeneous reaction is when all reactants and products are all at the same state(either gas, ligiud or aqueous (solid and solid ae less likely to react with each other)). If the reactants and products are not at the same state then it's a heterogenous reaction.

Extra Notes

The Kc can only be calculated when the reaction is at its equilibrium and it's a homogenous reaction.

Same experiment with same constant temperature can have different value of Kc due to the uncertainty of the apparatus use.

Rules for the unit of Kc:

Each terms have the unit of mol/dm3. If there is the same number of terms on the numerator and denominator then the unit cancel out. If there is 1 more term on the numerator then the unit is mol/dm3. Basically we can work out the unit by looking at the amount of terms in the numerator and denominator and subtract them.

Equilibrium constant expression:

Concentration of product is always the numerator (on top) and concentration of reactant is the denominator (at the bottom)

Each concentration is rasied to the power of its coefficient in the balance equation (the moles in the balance equation)

If there is more than 1 products or reactants. The terms are multiplied by each other.

General formula: