1st Law of Thermodynamics

The 1st Law of Thermodynamics is the Law of Conservation of Energy. Which specifically states energy can neither be created nor destroyed - only converted from one form of energy to another.

Types of Systems

1. Open - Matter and Energy can move freely.

2. Closed - Matter cannot move freely, but energy can.

3. Isolated - Matter and Energy cannot move freely.

Equation:

Physics: U = Q - W; Work is done by the system

Chemistry: U = Q + W; Work is done on the system

Note: W = (-) done by the system

W = (+) done on the system

Q = + (absorbs Heat) Endothermic

Q = - (loses Heat) Exothermic

2nd Law of Thermodynamics

The 2nd Law of Thermodynamics is the Law of Entropy which states that the state of entropy of the entire universe, as an isolated system, will always increase over time.

• Spontaneous Reactions:

Spontaneous reactions are exergonic, wherein energy is released during the reaction. These reactions occur once the conditions for the reaction is met, and don’t need an external energy input to create the reaction

Examples:

• Combustion reactions, such as the burning of wood, are typically spontaneous as they release energy.

• Dissolution of salt in water is a spontaneous process due to the increase in disorder.

• Non-spontaneous Reaction:

Non-spontaneous reactions are endergonic, wherein energy is needed to produce the reaction. These reactions occur when an energy input is made on the reactants. Sometimes, these reactions are reversible and can go “backwards” as well as “forwards.”

Examples:

• The electrolysis of water to produce hydrogen and oxygen gas is a non-spontaneous reaction under standard conditions. It requires an external electrical energy input to split water molecules.

• The synthesis of ammonia from nitrogen and hydrogen gas is another example of a non-spontaneous reaction that requires high pressure and temperature in the Haber process to proceed.

Thomsen-Berthelot Principle - almost all exothermic reactions are spontaneous.

Equation:

k = [AB]² / [A]² [B]

k = k_r / k_p

Example:

k = [Br₂][F₂]⁵ / [BrF₃]²

Le Chatelier’s Principle

Le Chatelier's Principle states that when a system at equilibrium is subjected to a stress (such as a change in temperature, pressure, or concentration), the system will adjust to partially counteract the effect of the stress and re-establish a new equilibrium state.

Factors that affect chemical equilibrium

• Concentration changes

A + 2B → C + D

→

The equilibrium shifts to the right if you increase the concentration of A;

A + 2B → C + D

←

and to the left, if you decrease the concentration of A.

• Pressure changes

A + 2B → C + D

→

The equilibrium moves to the right if you increase the pressure on the reaction;

A + 2B → C + D

←

and to the left, if you decrease the pressure on the reaction.

3 ways to change the pressure of an equilibrium mixture are:

1. Add or remove a gaseous reactant or product,

2. Add an inert gas to the constant-volume reaction mixture, or

3. Change the volume of the system.

• Temperature changes

A + 2B → C + D ∆H = +250 kJ mol^-1

←

The equilibrium moves to the left if you increase the temperature of the reaction;

A + 2B → C + D ∆H = -250 kJ mol^-1

→

and to the right, if you decrease temperature of the reaction.

• Addition of a Catalyst

Bronsted Acids and Bases

• A Brønsted-Lowry acid is any species that is capable of donating a proton -H⁺

• A Brønsted-Lowry base is any species that is capable of accepting a proton, which requires a lone pair of electrons to bond to the H⁺

• Water is amphoteric, which means it can act as both a Brønsted-Lowry acid and a Brønsted-Lowry base.

1. Brønsted Acid:

   • Example: Hydrochloric Acid (HCl)

     • Acidic Reaction: In water, hydrochloric acid donates a proton to water molecules, forming hydronium ions (H₃O⁺) and chloride ions (Cl⁻).

     • Chemical Equation: HCl + H₂O → H₃O⁺ + Cl⁻

2. Brønsted Base:

   • Example: Ammonia (NH₃)

     • Basic Reaction: Ammonia acts as a base by accepting a proton from water molecules, forming ammonium ions (NH₄⁺) and hydroxide ions (OH⁻).

     • Chemical Equation: NH₃ + H₂O → NH₄⁺ + OH⁻

Rate Law

The study of the rate of chemical reactions is called Chemical Kinetics

Rate = k[A]^x[B]^y

Orders

• Zero: A →B, Rate = k[A]⁰ — m¹s^-1

• 1st Order: A→B, Rate = k[B]¹ OR k[B] — s^-1

• 2nd Order: A→B, Rate = k[A]² — m^-1s^-1

• 3rd Order: A→B, Rate = k[A]³ — m^-2s^-1

Examples:

1. ClO^- (aq) + H₂O (l) → HClO (aq) + OH^- (aq) (fast)

I^- (aq) + HClO (aq) → HIO^- (aq) + Cl^- (aq) (slow)

OH^- (aq) + HIO (aq) → H₂O (l) + IO^- (aq) (fast)

Overall Reaction — ClO^- (aq) + I^- (aq) → Cl^- (aq) +IO^- (aq)

Intermediate — HIO

Molecularity for each step — Bimolecular

2. H₂ + ICl → HI + HCl

   HI + ICl → I₂ + HCl

Overall Reaction — H₂ + 2 ICl → I₂ + 2 HCl

Intermediate — HI

Rate — k[H₂][ICl]

Molecularity — Bimolecular

3. NO + NO → N₂O₂

   N₂O₂ + O₂ → 2 NO₂

Overall Reaction — 2 NO₂ + O₂ → 2 NO₂

Intermediate — N₂O₂

Rate — k[NO]²[O₂]

Molecularity — Termolecular

PPT

Beirut Explosion & Agent Orange

The Beirut Explosion is one the largest non-nuclear explosions in history. It occurred on August 4th, 2020, and had an explosive force of 1.1 kilotons of TNT(Trinitrotoluene). Which is equivalent to 3.3 Magnitude Earthquake.

It was caused by 2.75 kT of Ammonium Nitrate, a fertilizer, stored improperly with fireworks.

AMMONIUM NITRATE

NH₄NO₃

Ammonium nitrate is an explosive substance, but it’s used as a fertilizer.

2 NH₄NO₃ (s) → 2 N₂O (g) + 4 H₂O

"Agent Orange" is a chemical herbicide and defoliant. A tactical "rainbow herbicide". It was used by the US in the Vietnam War as requested by South Vietnam in order to remove the hiding advantage of the NVA.

(2,4-D) - DICHLOROPHENXYACETIC ACID

C₈H₆Cl₂O₃

(2,4,5-T) - TRICHLOROPHENXYACETIC ACID

C₈H₅Cl₃O₃

Attack of the Dead Men & The Halifax Disaster

The Attack of the Dead Men was an incident in WW1 between the Russian Empire and German Empire. The Germans attacked the Russian Forces with the Chlorine and Bromine Gas, incapacitating many Russian soldiers in the process. But the remaining Russians wrapped their faces in bandages charged at the German line, leading to the Germans seeing the resemblance of the Russians to the dead.

CHLORINE & BROMINE GAS

Br₂ + Cl₂ →Br + HCl

Bromine and Chlorine Gas combined with hydrogen in the air through water vapors creates hydrochloric acid and monatomic bromine.

On the morning of 6 December 1917, the French cargo ship SS Mont-Blanc collided with the Norwegian vessel SS Imo in the harbor of Halifax, Nova Scotia, Canada. Mont-Blanc, laden with high explosives, caught fire and exploded, devastating the Richmond district of Halifax. The explosion was the largest human-made explosion at the time, releasing 2.9 kT of TNT. (12 TJ)

TRINITROTOLUENE

C₇H₅N₃O₆ or C₆H₂(NO₂)₃CH₃

2 C₇H₅N₃O₆ → 3 N₂ + 5 H₂ + 12 CO + 2 C

BENZOL

C₆H₆

PICRIC ACID

C₆H₃N₃O₇

NITROCELLULOSE - GUN COTTON

C₆H₇O₂(OH)₃

Sarin Gas Attack & The Great London Smog

In 1995, members of the Aum Shinrikyo cult released sarin gas in the Tokyo subway system. This chemical weapon attack targeted Tokyo's busiest subway lines during rush hour.

SARIN

C₄H₁₀FO₂P

Sarin is a nerve agent that disrupts acetylcholine breakdown

In 1952, prolonged pollution and unusual weather patterns trapped smoke and pollutants over London, leading to a thick, deadly smog. Londoners burned high-sulfur coal, releasing sulfur dioxide (SO₂) into the air. The sulfur dioxide reacted with the oxygen, created sulfur trioxide (SO₃), then the sulfur trioxide reacted with water vapor to create sulfuric acid (H₂SO₄).

Formula 1:

2 SO₂ (g) ​+ O₂​ (g) → 2 SO₃ (g)

Formula 2:

SO₃ (g) + H₂O (g)→ H₂SO₄ (g)​