Chem Semester Exam

Chemical Bonding and Nomenclature Study Guide

Chemical Bonds:

1. Ionic Bonding

2. Covalent Bonding

3. Metallic Bonding

4. Covalent-Network Bonding

What is a chemical bond?

• Mutual electrical attraction between the nuclei and valence electrons of different atoms that binds the atoms together (minimizes potential energy and makes more atoms stable than when independent)

Ionic Bonding

What is Ionic Bonding?

• Chemical bonding that results from the electrical attraction between large numbers of cations and anions (transfer of electrons) 

• Also supports Law of Conservation of Matter

When bonding ionic compounds, you can ONLY transfer cations to anions.

ANY ionic compound is salt.

Covalent Bonding

• I- international

• U- union

• P - pure

• A - applied

• C - chemistry

What is Covalent Bonding?

• Chemical bonding  that results from the SHARING of electron pairs between two NON-METAL atoms (also called molecules)

What are the steps for Covalent Bonding?

1. Dot Notation

2. Sharing electrons with loops

3. Names

4. Drawing

5. Shape and Polarity

What are the naming rules?

1. First electron name stays the same

2. Second electron name change to -ide/-end

3. Use prefixes for subscripts

4. Never put mono on first element

What are the shapes?

1. Linear 

2. Bent

3. Trigonal Planor

4. Trigonal Pyramidel

5. Tetrahedral

What is the Covalent Bonding shortcut?

• Using math, determine how many electrons the atoms want and add them together, as well as determine how many electrons the atoms already have and add those together. Then subtract them and divide by 2

Metallic Bonding

What are molecular compounds?

• More complex than just a 1-2 shape molecule

What are structural formulas?

• Indicates the kind, number arrangement, and bonds but not the unshared pair of the electrons in a molecule

What is Metallic Bonding?

• Different form than ionic and covalent bonding. Differences come from the highly mobile valence electrons in a molecule

What elements use Metallic Bonding?

• Mostly transitional metals and underneath the stair case

Covalent-Network Bonding

What is Covalent-Network Bonding?

• Continuous network of bonded atoms (only non-metals) (ex. diamonds)

What are the structures of the 4 bonding types?

1. Ionic Compounds - Crystal Lattice

2. Covalent Bonding - Molecule Geometric Shapes

3. Metallic Bonding - Lattice (Substitutional and Interstitial)

4. Covalent-Network Bonding - Lattice and Geometric

Intermolecular Forces

What are Intermolecular Forces?

• Forces of attraction BETWEEN molecules

The covalent bond within a molecule is an intramolecular force

What is hydrogen bonding?

• When a hydrogen atom is bonded to an unshared pair of electrons in a nearby molecule

What is bond length?

• Distance between two bonded atoms at their minimum potential energy

What is bond energy?

• Energy required to break a chemical bond and form neutral isolated atoms

Water CANNOT conduct an electric current, it is ONLY when ions are in water.

Soap

What is soap made out of?

1. Lye, sodium hydroxide, potassium carbonate

2. Fats and oils

Lab

Analysis:

Examples:

Unit 6: Moles and Chemical Reactions

• Moles and Reactions

• Mole: A number (6.02 x 10²³)

• Amedeo Avogadro 🥑 (found the mole number)

• To find the mole in a compound (add the total mass of the 

elements = g/mole), which is the molar mass

• Counting with Moles

• 2 moles of Na₂S - 4 mol Na, 2 mol S

• 1 Dozen or 1 Mole

• Balancing Chemical Reactions

• Sodium + Chlorine → Sodium Chloride

• Na + Cl₂ → 2NaCl

• Rules of Balancing:

• Use mole (coefficients) in front of electrons/compounds

• Moles need to be whole numbers/reduced

• Never change subscripts

• Elements need to total the same on both sides

• DON’T start with oxygen or elements that are in multiple places

• Types of Chemical Reactions

• Synthesis (Direct Composition)

• A + B → AB

• Analysis (Decomposition)

• AB → A + B

• Single Replacement

• A + BC → B + AC

• Double Replacement

• AB + CD → CB + AD

• Combustion

• ? + O₂ → CO₂ + H₂O

• Formulas

• Chemical Formula: represents a compound or substance that has subscripts and symbols 

• EX: NaCl, H₂O, C₆H₁₁O₂

• Formula Unit (only ionic)

• EX: NaCl, CaF2

• Empirical Formula: 

• Covalent, but simplest ratio

• Molecular Formula: 

• Covalent, actual number of atoms in the compound, not simplest

• Structural Formula: 

• Typically only covalent, but maybe others 

• Demo 9 - Synthesis

• Magnesium + Oxygen → Magnesium Oxide

• 2Mg_(s) + O_2(g) -> 2MgO

• Has tongs holding up magnesium, lit it in fire, then produced light, watch glass underneath to catch ashes

• EX: flash bulb for old cameras 

• MgO uses - diets, photography, water, supplements, alloys, cars, and fireworks

• Hydrocarbons 

• CH₄ = Methane

• C₂H₆ = Ethane 

• C₃H₈ = Propane

• C₄H₁₀ = Butane

• C₅H₁₂ = Pentane

• C₆H₁₄ = Hexane

• C₇H₁₆ = Heptane

• C₈H₁₈ = Octane

• C₉H₂₀ = Nonane

• C₁₀H₂₂ = Decane

• Demo 10 - Double Replacement 

• Potassium  Iodide + Lead(II) Nitrate > Lead Diiodide + Potassium Nitrate

• 2KI_(aq) + Pb(NO₃)_2(aq) > PbI_2(s) + 2KNO_3(aq)

• Demo 11 - Single Replacement 

• Copper(II) + Silver Nitrate → Silver + copper nitrate

• Cu_(s) + 2AgNO_3(aq) → 2Ag_(s) + Cu(NO₃)_2(aq)

• Copper stick put into a flask that contained silver nitrate, the copper started crystallizing, water turned blue

• Chemical reactions don’t have to be immediate, some take time

• Reaction Symbols

• Catalysts - make chemical reactions go faster

• EX: Digestion (enzymes in body break down food to digest faster)

• Inhibitors - make chemical reactions go slower 

• EX: Refrigerator

• Demo 12 - Double Replacement with Decomposition

• Acetic Acid + Sodium Bicarbonate

• HC₂H₃O₂ + NaHCO₃ → NaC₂H₃O₂ + HCO₃

• Beaker container sodium bicarbonate (powder), then she poured acetic acid in the beaker with a flask, then it fizzed up.

Unit 7: Stoichiometry

What is stoichiometry?

• Comes from two greek words: 

• Stoichon → element

• Metron → measure

• When we do stoichiometry, we are saving time, money and resources

Examples: S’mores

3 Chocolate + 2 Graham Crackers + Marshmallows → S’more 

• Known: I want 50 s’mores for 50 juniors

• Unknown: How many boxes, bags of each ingredient do I need to buy?

- Need 13 chocolate bars (12 pubs in one bar so 4 people can use 1 bar)

Vocab Terms:

Limiting Reactant (L.R.)

- ex. chocolates

Excess Reactant (E.R.)

- ex. marshmallows and graham crackers

Theoretical Yield - (need limiting to find)

- ex. theoretically we can make 50 s’mores

Actual Yield - (will either be given or a reaction will have to take place to find it)

- ex. stuff happens, actually can only make 46 s’mores instead of the 50

Percent Yield 

• 46 actual s'mores50 theoretical x 100 = 92%

Mole Day Demo #13+14

Demo #13: Dry Ice

CO_2(s) - dry ice (-109℉)

• dry ice sublimes (solid to gas)

CO_2(s) + H₂O_(l) → H₂CO₃ (H₂O + CO₂)

What happened?

• We put water and pieces of dry ice into plastic water bottles and shut the caps tightly and threw them away from us. After they hit the ground, they blew up and created a loud noise

Demo #14: Sacrifice of a Gummy Bear

Potassium Chlorate → Potassium Chloride + Oxygen

2KClO₃ → 2KCl_(l + 3O_2(g)

△ - propane was used but not in the chemical equation, it was used as heat (catalyst)

4.73g1 x 1mol122g x 3mol2mol x 22.4L1mol = 1.30L

C₁₂H₂₂O₁₁ + 12O₂ → 11H₂O + 12CO₂

What happened?

• We heated the potassium chlorate until it became a liquid. We then put the gummy bear into the liquid and it exploded like a firework. The first reaction was decomposition, the second was combustion.

• KNOW the mole map

Molarity of Solutions

Molarity → the concentration of solutions

M =  molsliters

• Higher molarity means more concentrated

• Lower molarity means less concentrated

How do you make a solution?

Tools:

• Volumetric flasks

• Distilled water

Steps:

1. dH₂O

2. Add chemical

3. More dH₂O in the flask bottom

4. Even more dH₂O up to the meniscus line

• KNOW Part 1, 2, and 3 of the lab

Acids, Bases, and Salts Study Guide

The pH Scale

• pH = power/potential of hydrogen

• Examples above ^

Salts

• An ionic compound composed of a cation from a base and an anion from an acid

Example: Base + Acid → Salt + Water

• HCl + NaOH → NaCl + H₂O

Acids:

• A substance that produces hydronium ions when dissolved in water (donates H⁺)

• HCl + H₂O → H₃O⁺ + Cl^- 

• HCl and Cl are conjugate pairs 

• H₂O and H₃O are conjugate pairs

Conjugate pairs: one proton difference

Characteristics of Acids:

• Sour taste - citrus fruit, sour patch kids

• Changes color

• Conducts electric current

• Some react to metals to release H₂

• Have a pH of less than 7

Acid Examples:

• CH₃COOH in vinegar

• Ascorbic Acid (vitamin C)

• Carbonic Acid (H₂CO₃) in soft drinks

Bases

• A substance that produces hydroxide ions when dissolved in water (receives H⁺)

• NH₃ + H₂O → NH₄⁺ + OH^-

• NH₃ and NH₄ are conjugate pairs

• H₂O and OH are conjugate pairs

• On the reaction side, the NH₃ takes an H from the H₂O to produce NH₄

Characteristics of Bases:

• Bitter

• Changes Color (acid-base)

• Slippery 

• Conducts electric current

• pH greater than 7

Base Examples:

• Eggs

• Bleaches, soaps, toothpastes

• Seawater

Demo #15: pH Rainbow

• Never put water into acid, always put acid into water so the acid won’t splash back at you

Observations:

• Placed acid drops into a graduated cylinder after putting distilled water and indicator in and it turned yellow

• Base was then added to the side of the flask and so it slid to the bottom and created a rainbow with purple at the bottom (most basic) and red at the top (most acidic)

Logarithms

Exponential Formula:

b^x = y

• 2³ = 8 = 2x2x2

• 10³ = 1000

Logarithm Formula:

log_b y = x

• pH = -log[H⁺]

• [H⁺] units: molesliters = molarity

Examples of Concentration to pH:

1. HCl             -log(.0025) = 2.6

[H⁺]              pH = 2.6

.0025M

2. 0.525M       -log(.525) = 0.280

                    pH = 0.280

Examples of pH to Concentration:

10^-pH = M

1. pH = 11.35        10^-11.35 = 4.467x10^-12M

Demo #16: Neutralization of M.O.M.

M.O.M. → Milk of Magnesia

• Base (less hydrogens)

• pH = 10.5

• ACIDS HAVE MORE HYDRONIUM

• BASES HAVE MORE HYDROXIDE

Steps of the Demo:

1. Distilled water

2. M.O.M.

3. Universal indicator (turned it a deep purple color)

4. HCl (turned it pink-ish red at first

→ Quickly (even with the ice as an inhibitor) turned yellow to green to blue

Concentration of just the Hydrogen:

• pH10.5 = 10^-10.5 = 3.16 x 10^-11 M

Concentration of the entire M.O.M.:

• Magnesium Hydroxide

Mg(OH)₂

M = 1.414

Chemical Equation:

Mg(OH)₂ + 2HCl_(aq) → MgCl₂ + 2H₂O