Advanced Reaction Topics

Reaction Rates Reaction Rates Redox Chemistry Redox Chemistry Equilibrium Equilibrium Acids and Bases Acids and Bases

Reaction Rates

Things that affect the rate of a reaction Things that affect the rate of a reaction Temperature Temperature Increasing the temperature 10°C doubles the reaction rate (typically) Increasing the temperature 10°C doubles the reaction rate (typically) Concentration Concentration Surface Area Surface Area Catalysts & Enzymes Catalysts & Enzymes Every reaction is different and has a different reaction rate. Every reaction is different and has a different reaction rate.

Collision Theory Reactions happen when molecules collide with each other Reactions happen when molecules collide with each other The reaction only happens IF: The reaction only happens IF: They collide with enough energy They collide with enough energy They collide with the right orientation. They collide with the right orientation.

How Do They Relate? Things that affect the rate of a reaction Things that affect the rate of a reaction Temperature Temperature Increasing temperature increases the kinetic energy in a collision. Increasing temperature increases the kinetic energy in a collision. Kinetic energy is the energy of motion of an object Kinetic energy is the energy of motion of an object More collisions will have enough energy to have an effective collision More collisions will have enough energy to have an effective collision

How Do They Relate? Things that affect the rate of a reaction Things that affect the rate of a reaction Concentration Concentration Increases the number of particles in the same volume and therefore the number of collisions Increases the number of particles in the same volume and therefore the number of collisions Surface Area Surface Area Increases the accessible area for collisions Increases the accessible area for collisions

How Do They Relate? Things that affect the rate of a reaction Things that affect the rate of a reaction Catalysts and Enzymes Catalysts and Enzymes Lower the amount of energy needed for a reaction to take place, so more effective collisions result Lower the amount of energy needed for a reaction to take place, so more effective collisions result

Redox Chemistry

Electrolysis Run a current through water. Run a current through water. Splits water into hydrogen and oxygen Splits water into hydrogen and oxygen 2H 2 O  2H 2 + O 2 2H 2 O  2H 2 + O 2

Oxidation Numbers Describes the relative amount of electrons associated with a particular atom. Describes the relative amount of electrons associated with a particular atom.

Finding Oxidation Numbers 1. Every uncombined element in its natural state has an oxidation number of zero. 2. The oxidation number of a monatomic ion is its charge.

Finding Oxidation Numbers 3. Remember the following: Fluorine in a compound is always -1 Fluorine in a compound is always -1 Hydrogen is a +1 normally in a compound. It is -1 when a hydride. Hydrogen is a +1 normally in a compound. It is -1 when a hydride. Oxygen is almost always -2 in a compound unless it is a peroxide (-1) Oxygen is almost always -2 in a compound unless it is a peroxide (-1) 4. The sum of the individual oxidation numbers on every atom in a species is equal to the overall charge on that species.

Oxidation Numbers Practice Give the oxidation number of every element in the following compounds. BaCl 2

Oxidation Numbers Practice Give the oxidation number of every element in the following compounds. KNO 3

Oxidation Numbers Practice Give the oxidation number of every element in the following compounds. P 4

Oxidation Numbers WB Practice Give the oxidation number of every element in the following compounds. CaS MgF 2 HNO 3 H 2 O 2

Vanadium Oxidation States Vanadium oxidation states.mov Vanadium oxidation states.mov Vanadium oxidation states.mov Vanadium oxidation states.mov

Uses of Redox Chemistry Batteries Batteries Car batteries Car batteries Alkaline batteries Alkaline batteries Electroplating Electroplating Corrosion Corrosion

Equilibrium

Fishbowl Demo Rules: Rules: No “goal-tending” No “goal-tending” Get water in beaker, not around it Get water in beaker, not around it

Fishbowl Demo What are the characteristics once it reaches equilibrium? What are the characteristics once it reaches equilibrium? The amount of “reactants” and “products” is not changing The amount of “reactants” and “products” is not changing “Reactions” are still occurring in both the forward and reverse direction. “Reactions” are still occurring in both the forward and reverse direction. The rate of the “reactions” is the same at equilibrium The rate of the “reactions” is the same at equilibrium

Characteristics of Equilibrium The amounts of the reactants and products do not change while the system is at equilibrium. The amounts of the reactants and products do not change while the system is at equilibrium.

Characteristics of Equilibrium Consider: N 2 + 3H 2 ⇌ 2NH 3 Consider: N 2 + 3H 2 ⇌ 2NH 3 Notice the double half arrows

Characteristics of Equilibrium The forward and reverse reactions still both occur but at the same rate. The forward and reverse reactions still both occur but at the same rate. For this reason, equilibrium can also be called dynamic equilibrium For this reason, equilibrium can also be called dynamic equilibrium

Equilibrium Constants We can calculate the equilibrium constant for a reaction at equilibrium by measuring the concentrations of each species involved, then determining the ratio of products to reactants. We can calculate the equilibrium constant for a reaction at equilibrium by measuring the concentrations of each species involved, then determining the ratio of products to reactants. K eq >1 means that the reaction favors (makes more) products K eq >1 means that the reaction favors (makes more) products K eq <1 means that the reaction favors (makes more) reactants K eq <1 means that the reaction favors (makes more) reactants

Equilibrium Constants

Practice Problem

Practice Problem

Making Changes to an Equilibrium System How does changing the amount of one species affect the equilibrium? How does changing the amount of one species affect the equilibrium? An equilibrium system must respond to changes. An equilibrium system must respond to changes. A dynamic system must respond to any changes made. A dynamic system must respond to any changes made.

Le Chatelier's Principle “When a stress is placed on an equilibrium system, the equilibrium will shift to relieve that stress.” “When a stress is placed on an equilibrium system, the equilibrium will shift to relieve that stress.” The equilibrium may shift to the right The equilibrium may shift to the right To make more Products To make more Products To reduce the amount of Reactants To reduce the amount of Reactants The equilibrium may shift to the left The equilibrium may shift to the left To make more Reactants To make more Reactants To reduce the amount of Products To reduce the amount of Products

Le Chatelier's Principle CoCl 4 2– + 6H 2 O ⇌ Co(H 2 O) Cl – (blue)(pink) exothermic What is the stress on the equilibrium if 12M HCl is added? Which way does the equilibrium shift to relieve the stress? Why? What will it look like?

Le Chatelier's Principle CoCl 4 2– + 6H 2 O ⇌ Co(H 2 O) Cl – (blue)(pink) exothermic What is the stress on the equilibrium if H 2 O is added? Which way does the equilibrium shift to relieve the stress? Why? What will it look like?

Le Chatelier's Principle CoCl 4 2– + 6H 2 O ⇌ Co(H 2 O) Cl – (blue)(pink) exothermic What is the stress on the equilibrium if Ag + is added? Which way does the equilibrium shift to relieve the stress? Why? What will it look like?

Le Chatelier's Principle CoCl 4 2– + 6H 2 O ⇌ Co(H 2 O) Cl – (blue)(pink) exothermic What is the stress on the equilibrium if heat is added? Which way does the equilibrium shift to relieve the stress? Why? What will it look like?

Le Chatelier's Principle CoCl 4 2– + 6H 2 O ⇌ Co(H 2 O) Cl – (blue)(pink) exothermic What is the stress on the equilibrium if heat is removed (cooling)? Which way does the equilibrium shift to relieve the stress? Why? What will it look like?

Le Chatelier's Principle 2NO 2 (g) ⇌ N 2 O 4 (g) brownish red colorless exothermic If we cool the gasses which way does the equilibrium shift? Why? What will it look like?

Le Chatelier's Principle 2NO 2 (g) ⇌ N 2 O 4 (g) brownish red colorless exothermic If we warm the gasses which way does the equilibrium shift? Why? What will it look like?

Le Chatelier's Principle 2NO 2 (g) ⇌ N 2 O 4 (g) brownish red colorless exothermic If we release pressure on the gasses which way does the equilibrium shift? Why? What will it look like?

Acids and Bases

Hydrochloric Acid HCl(aq) HCl(aq) What type of compound is it? What type of compound is it? What type of electrolyte is hydrochloric acid? What type of electrolyte is hydrochloric acid?

Hydrochloric Acid Why does it light up? Why does it light up? What must be present in solution? What must be present in solution? Is hydrochloric acid an ionic compound? Is hydrochloric acid an ionic compound? No. It is in a small subset of covalent compounds. No. It is in a small subset of covalent compounds.

Hydrochloric Acid It must be making some ions in solution It must be making some ions in solution What are the ions? What are the ions? HCl + H 2 O  H 3 O + (aq) + Cl - (aq) HCl + H 2 O  H 3 O + (aq) + Cl - (aq)

Hydrochloric Acid H 3 O + is called the hydronium ion H 3 O + is called the hydronium ion Things that make hydronium ions in water are called acids. Things that make hydronium ions in water are called acids.

A Word About Hydronium Depending on how you look at it acids make Depending on how you look at it acids make H + - hydrogen ion H + - hydrogen ion H 3 O + - hydronium ion H 3 O + - hydronium ion The two are interchangable The two are interchangable H + + H 2 O  H 3 O + H + + H 2 O  H 3 O + Anytime you see one it can mean the other. Anytime you see one it can mean the other.

Common Acids Hydrochloric acid (HCl) Hydrochloric acid (HCl) Muriatic acid Muriatic acid Sulfuric acid (H 2 SO 4 ) Sulfuric acid (H 2 SO 4 ) Battery acid Battery acid Nitric acid (HNO 3 ) Nitric acid (HNO 3 ) Acetic acid (HC 2 H 3 O 2 ) Acetic acid (HC 2 H 3 O 2 ) Vinegar Vinegar Phosphoric acid (H 3 PO 4 ) Phosphoric acid (H 3 PO 4 ) Citric Acid Citric Acid Lactic Acid Lactic Acid Ascorbic Acid Ascorbic Acid Vitamin C Acetylsalicylic Acid Acetylsalicylic Acid Aspirin Stearic Acid Stearic Acid

Common Bases Sodium hydroxide Sodium hydroxide Lye, Caustic Soda Lye, Caustic Soda Calcium hydroxide Calcium hydroxide Lime Lime Magnesium hydroxide Magnesium hydroxide Milk of magnesia Milk of magnesia Ammonia Ammonia Sodium hypochlorite Sodium hypochlorite Bleach Sodium hydrogen carbonate Sodium hydrogen carbonate Baking Soda Calcium carbonate Calcium carbonate Chalk Tums

Acids and Bases Definitions Definitions Acid – a substance that dissociates and produces hydronium ions in water Acid – a substance that dissociates and produces hydronium ions in water Base – a substance that dissociates and produces hydroxide ions in water Base – a substance that dissociates and produces hydroxide ions in water

Acid and Base Definitions HCl (aq) + NaOH (aq)  NaCl + H 2 O HCl (aq) + NaOH (aq)  NaCl + H 2 O HCl dissociates and produces hydronium ions: HCl dissociates and produces hydronium ions: HCl (aq)  H + + Cl - HCl (aq)  H + + Cl - H + + H 2 O  H 3 O + H + + H 2 O  H 3 O + Acid Acid NaOH dissolves in water to form Na + and OH - NaOH dissolves in water to form Na + and OH - NaOH (aq)  Na + + OH - NaOH (aq)  Na + + OH - Base Base

Acid and Base Definitions Relations between the base definitions are not as simple. Relations between the base definitions are not as simple. NaOH dissolves in water to form Na + and OH - NaOH dissolves in water to form Na + and OH - Arrhenius Base Arrhenius Base NaOH + H +  Na + + H 2 O NaOH + H +  Na + + H 2 O Brønsted-Lowry Base Brønsted-Lowry Base Hydroxides are both Arrhenius and Brønsted-Lowry Bases. Hydroxides are both Arrhenius and Brønsted-Lowry Bases.

Acid-Base Definitions Monoprotic acid – an acid that has one ionizable hydrogen Monoprotic acid – an acid that has one ionizable hydrogen HCl, HNO 3 HCl, HNO 3 Diprotic acid – an acid that has two ionizable hydrogens Diprotic acid – an acid that has two ionizable hydrogens H 2 SO 4 H 2 SO 4

Acid-Base Definitions Triprotic acid – an acid that has three ionizable hydrogens Triprotic acid – an acid that has three ionizable hydrogens H 3 PO 4 H 3 PO 4 What kind of acid is acetic acid, HC 2 H 3 O 2 ? What kind of acid is acetic acid, HC 2 H 3 O 2 ? Monoprotic Monoprotic Typically only hydrogens written first are ionizable. Typically only hydrogens written first are ionizable.

Autolysis of Water Water spontaneously splits itself Water spontaneously splits itself 2H 2 O ⇌ H 3 O + + OH – 2H 2 O ⇌ H 3 O + + OH – An equilibrium system. An equilibrium system. Makes equal parts hydronium and hydroxide Makes equal parts hydronium and hydroxide Equal parts acid and base Equal parts acid and base Water is neutral. Water is neutral.

Autolysis of Water We will use brackets to represent molarity We will use brackets to represent molarity [H 3 O + ] is the molarity of the hydronium ion. [H 3 O + ] is the molarity of the hydronium ion. When acids and bases are dissolved in water [H 3 O + ][OH – ] = K w = 1x When acids and bases are dissolved in water [H 3 O + ][OH – ] = K w = 1x10 -14

Acid Base Reactions Look on your reference table Look on your reference table Most acid-base reactions fall under the category of double replacement; however, there are some that do not. Most acid-base reactions fall under the category of double replacement; however, there are some that do not. We are only going to consider the ones that are double replacement! We are only going to consider the ones that are double replacement!

Acid Base Reactions Acid Base Neutralization Reaction Acid Base Neutralization Reaction Hydrochloric acid and sodium hydroxide solutions are mixed Hydrochloric acid and sodium hydroxide solutions are mixed

Acid Base Reactions Acid Base Neutralization Reaction Acid Base Neutralization Reaction Acetic acid and barium hydroxide solutions are mixed. Acetic acid and barium hydroxide solutions are mixed.

Acid Base Reactions Acid Base Neutralization Reaction Acid Base Neutralization Reaction HA + B  A + HB HA + B  A + HB Transfer of hydrogen ions (H + ) Transfer of hydrogen ions (H + ) Hydrochloric acid and sodium sulfide solutions are mixed. Hydrochloric acid and sodium sulfide solutions are mixed.

Acids Hydrochloric acid Hydrochloric acid Is it an electrolyte? Is it an electrolyte? Why is it an electrolyte? Why is it an electrolyte? Acetic acid Acetic acid Is it an electrolyte? Is it an electrolyte? Why is it an electrolyte? Why is it an electrolyte? Why doesn’t it light up as much as hydrochloric acid? Why doesn’t it light up as much as hydrochloric acid?

Strength of Acids and Bases Hydrochloric acid completely dissociates Hydrochloric acid completely dissociates HCl + H 2 O  H 3 O + + Cl - HCl + H 2 O  H 3 O + + Cl - Acetic acid doesn’t make as many ions Acetic acid doesn’t make as many ions Acetic acid partially dissociates Acetic acid partially dissociates HC 2 H 3 O 2 + H 2 O ⇌ H 3 O + + C 2 H 3 O 2 – HC 2 H 3 O 2 + H 2 O ⇌ H 3 O + + C 2 H 3 O 2 – Around 0.5% of acetic acid molecules make hydronium ions Around 0.5% of acetic acid molecules make hydronium ions Reactant side is very favored. Reactant side is very favored.

Strength of Acids and Bases Strong acid or base – an acid or base that completely reacts with water to form hydronium ions or hydroxide ions. Strong acid or base – an acid or base that completely reacts with water to form hydronium ions or hydroxide ions. Strong acids – hydrochloric, sulfuric, nitric Strong acids – hydrochloric, sulfuric, nitric Strong bases – LiOH, NaOH, KOH, RbOH, CsOH, Ca(OH) 2, Sr(OH) 2, Ba(OH) 2 Strong bases – LiOH, NaOH, KOH, RbOH, CsOH, Ca(OH) 2, Sr(OH) 2, Ba(OH) 2

Strength of Acids and Bases Weak acid or base – an acid or base that partially reacts with water to form hydronium ions or hydroxide ions. Weak acid or base – an acid or base that partially reacts with water to form hydronium ions or hydroxide ions. Weak acids – everything except the strong acids Weak acids – everything except the strong acids Weak bases – everything except the strong bases Weak bases – everything except the strong bases

Strong Acid Weak Acid

Strength of Acids and Bases Strength does not describe concentration Strength does not describe concentration Consider Consider A bottle of “glacial” acetic acid (99%) A bottle of “glacial” acetic acid (99%) A bottle of concentrated sulfuric acid (98%) A bottle of concentrated sulfuric acid (98%) Both have (nearly) the same concentration Both have (nearly) the same concentration Acetic acid will not ionize as much in water as sulfuric acid will Acetic acid will not ionize as much in water as sulfuric acid will Acetic acid is a “weak” acid Acetic acid is a “weak” acid

Concentration of Acids If not all acids completely dissociate in water If not all acids completely dissociate in water The concentration of the acid molecules is different for every acid The concentration of the acid molecules is different for every acid The concentration of the hydronium ion in different acids is different The concentration of the hydronium ion in different acids is different Need a system that describes the concentration of acids. Need a system that describes the concentration of acids.

pH pH = -log [H 3 O + ] pH = -log [H 3 O + ] Also define a relationship for the amount of base Also define a relationship for the amount of base pOH = -log [OH – ] pOH = -log [OH – ]

How are pH and pOH related? How do you reverse a log? How do you reverse a log? 10 -pH = [H 3 O + ] 10 -pH = [H 3 O + ] 10 -pOH = [OH – ] 10 -pOH = [OH – ] 14 = pH + pOH

Practice Problems What is the pH of a solution with [H + ] of 1.0x10 -3 M? What is the pH of a solution with [H + ] of 1.0x10 -3 M?

Practice Problems What is the pOH of a solution with [H + ] of 1.0x10 -3 M? What is the pOH of a solution with [H + ] of 1.0x10 -3 M?

Practice Problems What is the [OH - ] of a solution with a pH of 9.00? What is the [OH - ] of a solution with a pH of 9.00?

Practice Problems What is the [OH - ] of a solution with an [H 3 O + ] concentration of 1.0x10 -5 M? What is the [OH - ] of a solution with an [H 3 O + ] concentration of 1.0x10 -5 M?

Practice Problems What is the pH of a solution with a hydronium ion concentration of 2.55x10 -4 M? What is the pH of a solution with a hydronium ion concentration of 2.55x10 -4 M?

Practice Problems What is the pOH of a solution that has a hydronium ion concentration of 5.50x10 -8 M? What is the pOH of a solution that has a hydronium ion concentration of 5.50x10 -8 M?

Indicators Colored compounds that are sensitive to changes in pH Colored compounds that are sensitive to changes in pH Indicators will change color based on how acidic or basic the conditions around it are Indicators will change color based on how acidic or basic the conditions around it are Chemical reaction with the acids or bases Chemical reaction with the acids or bases

Universal Indicator Universal Indicator is a mixture of different indicators. Universal Indicator is a mixture of different indicators. Resulting color depends on each of the four indicator’s states Resulting color depends on each of the four indicator’s states