Chemistry colloq 2

Question 1

Equilibrium

Answer 1

state in a reversible reaction where the rate of the forward reaction is equal to the rate of the reverse reaction, resulting in no net change in the concentrations of the reactants and products over time.

Question 2

2 types of equilibriums:

Answer 2

Homogeneous equilibrium: All reactants and products are in the same
state (e.g all gaseous)

Heterogeneous equilibrium: Reactants and products are in different
states

Question 3

1. If ΔG∘ < 0, the reaction is spontaneous under standard conditions, and
   the equilibrium will favor WHAT?
2. If ΔG∘ = 0, the reaction is non-spontaneous under standard conditions and the equilibrium will favor WHAT?
3. If ΔG∘ > 0, the reaction is non-spontaneous under standard conditions,
   and the equilibrium will favor the WHAT? (small Keq)

Answer 3

1. Products
2. Reactants
3. Reactants

Question 4

Le Chatelier’s principle:

Answer 4

“If a dynamic equilibrium is disturbed by changing the conditions, the
position of equilibrium will shift to counteract the change”

A+B ⇋ C+D

Question 5

4 things that can be added to chemical equilibrium

Answer 5

Concentration
Pressure
Temperature
Catalyst

Question 6

How change of concentration affects equilibrium
A+B ⇋ C+D

Answer 6

Increase in Reactants:
Adding more of a reactant causes the
equilibrium to shift to the right (toward the products) to consume the
added reactant.

Decrease in Reactants: Removing a reactant causes the
equilibrium to shift to the left (toward the reactants) to replace the
lost reactant.

AND VICE VERSA WITH PRODUCTS

Similarly, changes in the concentration of products will have the
opposite

Question 7

How change of pressure affects equilibrium
A+B ⇋ C+D

Answer 7

If pressure is increased by reducing the volume of the
system, the equilibrium shifts toward the side with fewer gas
molecules to reduce pressure.

If pressure is decreased (by increasing volume), the
equilibrium shifts toward the side with more gas molecules.

Question 8

How change of temperature affects equilibrium
A+B ⇋ C+D

Answer 8

• For an exothermic reaction (releases heat): Increasing temperature shifts the equilibrium to the left (toward reactants) as the system attempts to absorb the added heat.
• For an endothermic reaction (absorbs heat): Increasing
  temperature shifts the equilibrium to the right (toward products).

Question 9

Addition of a Catalyst

Answer 9

A catalyst speeds up the rate at which equilibrium is reached but does not shift the position of the equilibrium itself. It lowers the activation energy for both the forward and reverse reactions equally

Question 10

Dissociation Degree (α)

Answer 10

The degree of dissociation (α) refers to the how much of a substance
has dissociated into ions or smaller molecules when it dissolves in a
solvent

Question 11

Dissociation Degree (α)

numbers. Explainish

Answer 11

Question 12

Equilibrium Constant (Keq)

Answer 12

The equilibrium constant (Keq) describes the ratio of the concentrations of products to reactants at equilibrium for a reversible chemical reaction.

aA + bB ⇌ cC + dD

Exempel

Question 13

Solubility product constant (Ksp)

Answer 13

The solubility product constant (Ksp) is the equilibrium constant for the dissolution of nearly insoluble salts in a solution.

Ksp= [A+] × [B−]

[A+] is the concentration of the cation (A) in the solution at equilibrium.

[B−] is the concentration of the anion (B) in the solution at equilibrium.

Question 14

Ostwald’s dilution law and
Dissociation equilibrium constant
(Edis) OR (Kdis)

Answer 14

Ostwald’s dilution law is used to calculate the dissociation equilibrium
constant (Edis)

The dissociation equilibrium constant (Edis) describes the equilibrium
of the dissociation of a weak electrolyte in a solution.

Question 15

Common Ion Effect

Answer 15

The solubility of a salt decreases when a solution** already contains** one of the ions present in the salt, due to the shift in equilibrium to counteract the
change.

Question 16

Complex Compounds

• Structure of Complex Compound
• Central Metal Ion:
• Ligands:

Answer 16

• consist of a central metal ion or atom bound to surrounding ligands, which can be atoms, ions, or molecules.

Central metal
Definition: The metal ion or atom at the core of the complex.
Characteristics: Typically transition metals with varying oxidation
states.
Coordination Number: The number of ligand atoms directly bonded to
the central metal.

Ligands:
Definition: Molecules or ions that coordinate to the central metal.
Types: Monodentate (bind through a single site), bidentate (bind
through two sites), polydentate (bind through multiple sites).
Common Ligands: Water (H₂O), ammonia (NH₃), cyanide (CN⁻),
ethylenediamine (en), oxalate (C₂O₄
²⁻).

Question 17

Stability of Complex Compounds

NOT IMPORTANT

Answer 17

Question 18

Dissociation types:

Differences

Answer 18

Primary Dissociation

Definition: The initial breaking of ionic bonds, often releasing simple
ions or molecules.

Examples: Dissociation of [Co(NH₃)₆]Cl₃ into [Co(NH₃)₆]³⁺ and Cl⁻
ions.

Contributing Factors: Solubility in water, ionic strength of the medium,
and temperature.
———————————-
Secondary Dissociation

Definition: The breaking of covalent/coordination bonds, leading to
further disintegration of the complex.

Examples: Decomposition of [Co(NH₃)₆]³⁺ into Co²⁺ and ammonia
molecules.

Contributing Factors: Acid-base reactions, redox reactions, thermal
stability

Question 19

Acids, Bases, and Salts:

Answer 19

Acids: Substances that donate H⁺ ions; categorized into strong (e.g., HCl, HNO₃) and weak acids (e.g., CH₃COOH). Strong acids fully ionize in water, while weak acids partially ionize.

Bases: Substances that accept H⁺ ions or donate OH⁻ ions; include strong bases (e.g., NaOH) that fully dissociate and weak bases (e.g., NH₃) that partially dissociate.

Salts: Formed by the neutralization reaction between acids and bases, with types (neutral, acidic, basic) determined by the strength of the acid and base from which they
derive.

Question 20

pH and pOH

Answer 20

pH measures acidity (pH < 7), neutrality (pH = 7), or alkalinity (pH > 7) of solutions.
Formulas for calculating pH, pOH, and dissociation constants (Ka, Kb, pKa, pKb) were introduced.

Question 21

Brønsted-Lowry Theory:

Answer 21

Defines acids as proton donors and bases as proton acceptors. Discusses conjugate acid-base pairs formed during reactions.

Question 22

pH effects on the Body:

NOT VERY IMPORTANT

Answer 22

Strong acids and bases can cause tissue damage. Conditions like acidosis (pH < 7.35) and alkalosis (pH > 7.45) disrupt physiological balance, with significant impacts on the nervous, cardiovascular, and respiratory systems.

Question 23

Salt Hydrolysis

Answer 23

Explains how salts influence solution pH depending on the acid-base strengths of their components (neutral, acidic, or basic salts).

Question 24

Colligative Properties:

Answer 24

Properties like
- vapor pressure lowering
-boiling point elevation
- freezing point depression
- osmotic pressure

depend on solute particle number, not identity.

Question 25

Osmosis and Osmotic Pressure:

Answer 25

Describes solvent movement across membranes, driven by solute concentration differences.

Provides formulas for calculating osmotic pressure.

Question 26

Solution Tonicity

Answer 26

Defines
- isotonic (equal solute concentration)
- hypertonic (higher solute concentration outside cells)
- hypotonic solutions (lower solute concentration outside cells)

and
their medical applications.

Question 27

General Principles of Potentiometric Titration:

not very important

Answer 27

Potentiometric titration tracks the potential change of a solution during a chemical reaction, using electrodes to monitor the equivalence
point without the need for visual indicators.

Question 28

Equivalence Point (Reaction End-Point):

Answer 28

The equivalence point is where the titrant and analyte react in exact stoichiometric proportions, marked by a sharp potential change on the titration curve

Question 29

Buffer Region

Answer 29

The buffer region is the part of the curve where the solution resists pH or potential changes,
caused by the coexistence of a weak acid/base and its conjugate pair.

Question 30

Half-Neutralization Point:

Answer 30

The half-neutralization point occurs when half the analyte is neutralized, and the pH (or potential) at this point corresponds to the pKa (or pKb) of the analyte.

Question 31

Using Titration Graph to Recognize Electrolytes

Answer 31

The shape and features of the titration curve, such as initial pH, buffer regions, and equivalence point behavior, help identify whether the substances are strong/weak acids,
bases, or redox agents.

Question 32

What is a buffer system?

Answer 32

A buffer system is a solution that resists changes in pH when:

small amounts of acid (H⁺ ions) or base (OH⁻ ions) are added.

Question 33

The 4 main elements of a buffer

Answer 33

1. Weak Acid and its Conjugate Base (Salt):
- Example: Acetic acid (CH3COOH) and acetate (CH3COO−).

• These components react with added bases or acids to stabilize pH.

2. Weak Base and its Conjugate Acid (Salt):
- Example: Ammonia (NH3) and ammonium ion (NH4+).

• These components function similarly but in systems where bases are more prevalent.

3. Weak bivalent acid and its acidic salt (The weak acid can
donate two protons (H⁺)
- Example: H2CO3 (weak bivalent acid) and HCO3- (acidic salt/conjugate base)

• These components function similarly but in systems where
  bases are more prevalent.

4. Two salts of the same polyvalent acid (differing in 1 hydrogen ion)
- The salt that contains greater number of H + acts as the acid in a buffer system

Question 34

Principles of Maintaining pH in
Buffer Systems

Answer 34

𝐻𝐴 ⇔ 𝐻+ + 𝐴−

Le Chatelier’s Principle:

When an external change (like addition of H+ or OH−) disturbs the
equilibrium of the buffer system, the system adjusts by shifting the
equilibrium to minimize the change. (see explanation above)

Question 35

DO YOU RECOGNISE??

Question 36

Example

Question 37

Buffer capacity (β)

3 components

Answer 37

The ability of a buffer solution to resist
changes in pH when small amounts of acid or base are added. It
measures the “strength” of a buffer in maintaining a stable pH. Unit is
mol/L.

* Concentration of buffer components: Higher concentrations of
the weak acid (HA) and its conjugate base (A−) result in a higher
buffer capacity.

*Ratio of acid to base: Buffer capacity is maximum when the
concentrations of the weak acid and its conjugate base are equal
(pH = pKa).

* Volume of the buffer: Larger volumes have greater buffer capacity
because they can neutralize more added acid/base without
significant pH changes.

Question 38

Calculations buffer capacity

Question 39

Effective buffer pH region

• range

Answer 39

Question 40

Buffer system in human body

pH in human blood

Applications in medicine

Answer 40