[CHEMICAL REACTIONS] Chemical Equilibria ➡️ Reaction Stoichiometry

Proverbs 16:3

TRUE

[CHEMICAL EQUILIBRIA]

TRUE OR FALSE:

Reversible reactions are the only one that have equilibrium

TRUE

[CHEMICAL EQUILIBRIA]
TRUE OR FALSE:

Irreversible reactions cannot have equilibrium

TRUE

[CHEMICAL EQUILIBRIA]
TRUE OR FALSE:

Once a reversible reaction is finished, there will be stagnation in the number of reactants and products (i.e. equilibrium). At this point, the rate of forward and backward reactions (which have been always changing before equilibrium) now become constant.

$$K_{eq} = [products] / [reactants]$$

[CHEMICAL EQUILIBRIA]

Equilibrium constant:

TRUE

[CHEMICAL EQUILIBRIA]

TRUE OR FALSE:
High $K_{eq}$ → More Product

TRUE

[CHEMICAL EQUILIBRIA]
TRUE OR FALSE:
Low $K_{eq}$ → More Reactant

TRUE

[CHEMICAL EQUILIBRIA]
TRUE OR FALSE:
Some factors ("stresses") may once again change the forward and backward reactions.

Stress

[CHEMICAL EQUILIBRIA]

_____ disturbs the balance the equilibrium

Le Chatelier’s principle

[CHEMICAL EQUILIBRIA]
The _______ states that a stress given to a reaction in equilibrium will be balanced by shifting the reaction away from that stress.

• Concentration

• Pressure

• Temperature

[CHEMICAL EQUILIBRIA]

Possible Sources of Stress [3]

Table 20. Stresses covered by the Le Chatelier's principle

• Increase something – shift away from that side ("common ion effect")

• Decrease something – shift to that side

Example:

[Le Chatelier’s principle Possible Sources of Stress]

How the reaction shifts in Concentration:

Common-ion effect

[Le Chatelier’s principle Possible Sources of Stress]

_______ was the creation of more precipitate

Make sure first that

1) all reactants and products are gases

2) there is inequality in total moles (focus on the side with MORE moles)

Example: just assume that these are gases

• Increase pressure – shift away from that side

• Decrease pressure – shift to that side

If volume, analyze in reverse (P and V are inversely proportional as per the Boyle's law)

Example [1]

Example [2]

Since both side are thesame, there will be no effect (no shift will happen either forwar or backward)

[Le Chatelier’s principle Possible Sources of Stress]

How the reaction shifts in Pressure:

Determine first of the reaction is exothermic or endothermic

If exothermic, imagine heat to be a PRODUCT

• Heating – to reactant (backward)

• Cooling – to product (forward)

Example:

If endothermic, imagine heat to be a REACTANT

• Heating – to product (forward)

• Cooling – to reactant (backward)

Example:

[Le Chatelier’s principle Possible Sources of Stress]

How the reaction shifts in Temperature:

Unsaturated solution

More solute dissolves

a. Unsaturated solution

b. Saturated solution

c. Supersaturated solution

Saturated solution

No more solute dissolves

a. Unsaturated solution

b. Saturated solution

c. Supersaturated solution

Supersaturated solution

Added crystals grow

a. Unsaturated solution

b. Saturated solution

c. Supersaturated solution

• Acid-base equilibria

• Solubility equilibria

• K_a and K_b [meaning]

• K_sp [meaning]

• Unsaturated solution

• Saturated solution

• Supersaturated solution

Specific equilibrium examples:

a) Acid-base equilibria – K_a and K_b (refer to part VI)

b) Solubility equilibria K_sp (compared with ions in sample "Q")

• If Q < K_sp: _____

• If Q = K_sp: _____

• If Q > K_sp":_______

Stoichiometry

[REACTION STOICHIOMETRY]
______ deals with the quantity of reactants and products involved in chemical reactions

Limiting reagent

[REACTION STOICHIOMETRY]
______is a substance completely consumed in a chemical reaction. If this runs out, reaction stops.

Excess reagent

[REACTION STOICHIOMETRY]
______ is a substance present in quantities greater than needed for the limiting reagent.

Excess reagent

[REACTION STOICHIOMETRY]
If the limiting reagent runs out, the ______ is left behind.

Theoretical yield

[REACTION STOICHIOMETRY]
_______is the amount of product created based purely on calculation

Actual yield

[REACTION STOICHIOMETRY]

_______ is the amount of product created based purely on what is reflected in the actual experiment

Percent yield

[REACTION STOICHIOMETRY]

______ is the ratio of the actual yield to the theoretical yield ((AY/TY) x 100%)