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Unit Four Note Packet�Chemical Reactions��Name: ___________________

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Video #1

Intro to Reactions, Review of Chemical and Physical Changes

Physical Change Similarities Chemical Change_____

Occurs when a substance Occurs when a substance is

undergoes a change in: transformed:

Examples: Examples:

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End of Video #1

Practice: Identify the particle diagrams as either a physical or a chemical change.

Why? Why?

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Video #2

Gas Stoichiometry

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Video #2�Gas Stoichiometry

Because PV=nRT has MOLES, can use it as a gateway to stoichiometry
Use PV=nRT to calculate moles, then use coefficients to turn mol A into mol B
OR use PV=nRT to convert mol A or B into P, V, or T

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Video #2

Gas Stoichiometry

What is the volume of CO₂ produced at 37⁰C and 1.00 atm when 5.60 g of glucose are used up when glucose is combusted?

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End of Video #2�Example – Try it!

Consider the reaction:

What mass of mercury (II) oxide is necessary to produce 0.248L of oxygen gas at 25°C and 1.5 atm?

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Video #3

Solution Stoichiometry

Using molarity as a new stoich tool

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Solution Stoichiometry

Converting between M of A to M or V of B
Molarity&volume A 🡪 mol A
Moles A 🡪 moles B (use coefficients here – need balanced chemical equation!)
Moles B 🡪 Molarity or liters B

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Solution Stoichiometry

List the species present in the combined solution before any reaction occurs, and decide what reaction will occur.
Write the balanced net ionic equation for this reaction.
Calculate moles of reactants.
Determine the limiting reactant, where appropriate.
Calculate the moles of the required reactant or product.
Convert to grams or volume (of solution), as required.

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Acid–Base Titrations

Titration – delivery of a measured volume of a solution of known concentration (the titrant) into a solution containing the substance being analyzed (the analyte).

Frequently used to determine molarity

Equivalence point – enough titrant added to react exactly with the analyte.
Endpoint – the indicator changes color so you can tell the equivalence point has been reached.

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Question

What is the molarity of an NaOH solution if 48.0 mL is needed to neutralize 35.0 mL of 0.144 M H₂SO₄?

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End of Video #3

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Video #4

Oxidation and Reduction (Review)

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Video #4�Redox Fundamentals (Review)

Oxidation: loss of electrons
Reduction: gain of electrons

LEO the lions says GER
LEO = loss of electrons, oxidation
GER = gain of electrons, reduction

Redox rxns result in electric current
Called ELECTROCHEMISTRY!

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Video #4�Reminder = ox, red AGENTS

Oxidizing agent = species that helps something ELSE become oxidized

It itself becomes reduced!

Reducing agent = helps something else reduce

It itself becomes oxidized!

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Video #4�Redox redux

2Mg (s) + O₂ (g) 2MgO (s)

2Mg 2Mg²⁺ + 4e^-

O₂ + 4e^- 2O^2-

Oxidation (lose e^-)

Reduction (gain e^-)

Electrochemical process = redox rxn where:

energy released by spont. rxn converted to electricity OR
electrical energy used to cause a nonspont. rxn to occur

0

2+

2-

If you consider Mg and O separately:

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End of Video #4�Redox Equations

Conservation of charge: e^- not lost in a chemical rxn
Nof e^- on left = nof e^- on right
Half-reactions separate red from ox
Show e^- as reactant or product
Sn²⁺(aq) + 2Fe³⁺(aq) 🡪 Sn⁴⁺(aq) + 2Fe²⁺(aq)
Ox. half reaction: e^- are products, lost; charge on species increases

Sn²⁺(aq) 🡪 Sn⁴⁺(aq) + 2e^-

Red. half reaction: e^- are reactants, gained; charge on species decreases

2Fe³⁺(aq) + 2e^- 🡪 2Fe²⁺(aq)

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Video #5

Dissolving vs. Dissociating
Electrolytes

Strong vs. Weak vs. Non
What compounds are in each category?

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Video #5�Solutes: Dissolving vs. Dissociating

Dissolving – process of forming a homogeneous mixture with a solvent

Dissociating – splitting into ions during the dissolving process
Ex.
Ex.

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Video #5�How would the following soluble ionic compounds dissociate?

NH₄Br

CaCl₂

Mg(NO₃)₂

K₃PO₄

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Video #5�Electrolytes

What is an electrolyte?

Why does it conduct?

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Video #5 - Electrolytes

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Video #5�Strong / Weak / Non Electrolytes

Strong

Weak

Non

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Video #5�Recognizing soluble salts

Ions that, if present, will produce a water soluble compound:

Ions that are GENERALLY soluble:

Ions that are GENERALLY insoluble:

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Seven Strong Acids: Completely Donate their proton(s) (complete dissociation)

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Eight Strong Bases: Completely dissociate from their hydroxide

Group 1A metal hydroxides

Heavy group 2A metal hydroxides

Forms lowercase “b” in per table
These hydroxides are also soluble!

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�All acids and bases other than 7SA/8SB are weak!

Video #5

Weak Electrolytes – What compounds are they?

Incomplete dissociation 🡪 partially ionized
Do not donate proton or generate hydroxide completely

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End of Video #5�Nonelectrolytes

NO dissociation

Molecular compounds: No ions involved so no current!
Insoluble salts (solubility rules)
Solids, liquids, gases

must be (aq) to be an electrolyte!

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Practice

The diagrams below show three compounds, AB₂(1), AC₂(2), AD₂(3), dissolved in water. Put them in order from strongest to weakest electrolyte.

(1)

(2)

(3)

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Video #6

Aqueous Reactions

Precipitation
Particle Diagrams

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Video #6�Types of Aqueous Reactions

Precipitation
Acid–Base
Oxidation–Reduction

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Video #6�Precipitation Reaction

Double replacement reaction in which a solid forms and separates from the solution.

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Video #6 - Precipitation Reaction

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End of Video #6 - The Reaction of K₂CrO₄(aq) and Ba(NO₃)₂(aq)

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Try it – Draw a molecular-level representation of the product mixture

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Determine the products and identify the precipitate in the following reactions

Aqueous solutions of calcium chloride and sodium carbonate are mixed.

Aqueous solutions of aluminum chloride and potassium hydroxide are mixed.

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Video #7

A/B Definitions
Dissociation Reactions
Polyprotic acids

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Video #7�Definitions of Acids and Bases

Arrhenius: Acids produce H⁺ ions in solution, bases produce OH^- ions
Brønsted–Lowry: Acids are proton (H⁺) donors, bases are proton acceptors

HCl + H₂O → Cl^- + H₃O⁺

CO₃^2- + H₂O ↔ HCO₃^1- + OH^-

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Video #7�Amphoterism

Amphoteric substances behave as both acids and bases

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Video #7 - Strong vs. Weak Acids

Strong acids (SA) –

Weak acids (WA) –

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Video #7 – �Acid Dissociation Rxns (K_a)

When acid added to water, dissociates into ions, donates H⁺ to water

i.e. acts like an acid!

Can be shortened as:

IF SA (strong acid), then this rxn is one way
IF WA (weak acid), then rxn is in equilibrium

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Video #7�Base Dissociation Rxns (K_b)

When base added to water, accepts a proton FROM WATER

i.e. ACTS LIKE A BASE!

IF SB, then rxn is one way
IF WB, then rxn is in equilibrium

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Video #7�Try it!

Write the acid dissociation rxn for acetic acid

Write the base dissociation rxn for ammonia, NH₃ (btw learn the formula for ammonia NOW)

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End of Video #7�Polyprotic Acids

Monoprotic acids: only one ionizable proton
Polyprotic acids: more than one ionizable proton

KEY:

First acid dissociation (K_a1) rxn for sulfurous acid:

Second acid dissociation (K_a2) rxn for sulfurous acid:

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Video #8

Conjugate A/B Pairs
How to determine if a salt is acidic, basic, or neutral

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Video #8�Conjugate acids and bases

HA(aq) + H₂O(l) H₃O⁺(aq) + A^-(aq)

Conjugate base:

Conjugate acid:

Conjugate acid-base pair:

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Video #8 - Question

What is the conjugate base of each of the following acids: HClO₄, H₂S, PH₄⁺, HCO₃^-?

What is the conjugate acid of each of the following bases: CN^-, SO₄^2-, H₂O, HCO₃^-?

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The stronger an acid, the weaker its conjugate base

Weak acids have weak conjugate bases
Ex. HCl vs. HC₂H₃O₂

Strengths of A/B

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Video #8�Strengths of A/B

Strong acid:

Completely dissociate

Have far more products than reactants

Yields a weak conjugate base

Conjugate base is much weaker base than water

Weak acid:

Incompletely dissociate

Have far more reactants than products

Weaker the acid, stronger its conjugate base

Conjugate weak base is stronger base than water

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Video #8 - Evaluating Salts as Acidic/Basic/Neutral

Consider each ion in a salt and ask if it is a conjugate of a SA/WA or SB/WB
Ex. NH₄Cl and NaBr

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End of Video #8�Evaluating Salts as Acidic, Basic, or Neutral

Na₂CO₃

KCl

FeBr₃

CaF₂

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Video #9

Net Ionic Equations (choose either A, B, C, or D videos)

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Video #9

Net Ionic Equations (choose either A, B, C, or D videos)

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Video #9

Net Ionic Equations (choose either A, B, C, or D videos)

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Video #9

Net Ionic Equations (choose either A, B, C, or D videos)

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Video #9

Net Ionic Equations (choose either A, B, C, or D videos)