Chemistry Final Exam Study Guide Notes

Semester 1

Types of Chemical Bonds

• Ionic Bond: Formed between a metal and a nonmetal due to the transfer of electrons.
• Covalent Bond: Formed between two nonmetals due to the sharing of electrons.

Determining Bond Type

• To determine whether elements will form an ionic or covalent bond, consider their electronegativity difference. A large difference typically indicates an ionic bond, while a small difference indicates a covalent bond.
  • Strontium and oxygen: Ionic
  • Nitrogen and fluorine: Covalent
  • Sulfur and chlorine: Covalent
  • Potassium and nitrogen: Ionic

Naming Ionic Compounds

• Calcium Fluoride: $CaF_2$
• Sodium Oxide: $Na_2O$

Formulas for Ionic Compounds

• Lithium Oxide: $Li_2O$
• Magnesium Chloride: $MgCl_2$

Identity of an Atom

• The number of protons determines the identity of an atom. This is also known as the atomic number.

Subatomic Particles

• Gallium-70:
  • Protons: 31
  • Neutrons: 39
  • Electrons: 31
• Strontium-87:
  • Protons: 38
  • Neutrons: 49
  • Electrons: 38
• Tin-119:
  • Protons: 50
  • Neutrons: 69
  • Electrons: 50

Isotopes

• Isotopes are atoms of the same element with different numbers of neutrons, leading to different mass numbers.

Organization of the Periodic Table

• The modern periodic table is organized by increasing atomic number (number of protons) and grouped by similar chemical properties.

Valence Electrons

• Lithium (Li): 1
• Neon (Ne): 8
• Helium (He): 2
• Oxygen (O): 6

Characteristics of Metals

• Characteristics: Luster, conductivity, malleability, ductility, lose electrons to form cations.
• Location: Left side of the periodic table.

Characteristics of Nonmetals

• Characteristics: Dull, nonconductive, brittle, gain electrons to form anions.
• Location: Right side of the periodic table.

Periodic Trends

• More electronegativity: Br
• Higher ionization energy: Br
• Smallest atomic radius: Br
• Greater electron affinity: Br

Groups on the Periodic Table

• Alkali Metals: Group 1, 1 valence electron
• Alkaline Earth Metals: Group 2, 2 valence electrons
• Halogens: Group 17, 7 valence electrons
• Noble Gases: Group 18, 8 valence electrons (except Helium, which has 2)

Balancing Chemical Equations

• $1 C + 1 S<em>8 → 1 CS</em>2$
• $6 Cs + 1 N<em>2 → 2 Cs</em>3N$

Law of Conservation of Mass

• The law of conservation of mass states that mass is neither created nor destroyed in a chemical reaction. The number of atoms of each element must be the same on both sides of the equation.

Semester 2

Molar Mass

• Water ($H_2O$): $(2 \times 1.008) + 16.00 = 18.016$ g/mol
• Methane ($CH_4$): $12.01 + (4 \times 1.008) = 16.042$ g/mol

Mole Road Map

• The mole road map is used to convert between mass, moles, and number of particles using molar mass and Avogadro's number ($6.022 \times 10^{23}$).

• Number of molecules in 1.20 moles of $O_2$: $1.20 \text{ moles} \times (6.022 \times 10^{23} \text{ molecules/mole}) = 7.23 \times 10^{23}$ molecules

• Mass in grams of 4.10 moles of $H_2O$: $4.10 \text{ moles} \times 18.016 \text{ g/mole} = 73.8656$ g

Activity Series Table

• The activity series table is a list of elements ranked in order of their reactivity. Elements higher on the list will displace elements lower on the list in a single replacement reaction.

Exothermic and Endothermic Reactions

• Exothermic Reaction: A reaction that releases heat to the surroundings. The change in enthalpy ($\Delta H$) is negative.
• Endothermic Reaction: A reaction that absorbs heat from the surroundings. The change in enthalpy ($\Delta H$) is positive.

Graphs of Exothermic/Endothermic Reactions

• Exothermic reactions show a decrease in energy as reactants convert to products.
• Endothermic reactions show an increase in energy as reactants convert to products.

Classifying Reactions

• $N<em>2 (g) + O</em>2 (g)+ 180 \text{ kJ} → 2NO (g)$: Endothermic
• $2NO<em>2 (g) → N</em>2O_4 (g) + 57.6 \text{ kJ}$: Exothermic
• $PCl<em>3 (g) + Cl</em>2 (g) → PCl_5 + 92.5 \text{ kJ}$: Exothermic

Catalysts

• A catalyst lowers the activation energy of a reaction, providing an alternate pathway. Catalysts do not change whether a reaction is exothermic or endothermic.

Latent Heat

• Latent Heat of Fusion: The heat required to change a substance from a solid to a liquid at its melting point.
• Latent Heat of Vaporization: The heat required to change a substance from a liquid to a gas at its boiling point.

Heating Curve

• Segments:
  • Temperature change: Specific heat
  • Phase change: Latent heat

Specific Heat Calculation

• Formula: $q = mc\Delta T$, where q is heat, m is mass, c is specific heat, and $\Delta T$ is the change in temperature.
• $q = (15 \text{ g}) \times (7.2 \text{ J/g°C}) \times (85°C - 25°C) = 6480 \text{ J}$

Mass Calculation

• Using $q = mc\Delta T$, rearrange to solve for mass: $m = q / (c\Delta T)$
• $m = 8750 \text{ J} / (0.9025 \text{ J/g°C} \times 65°C) = 149.1 \text{ g}$

Factors Affecting Reaction Rate (Collision Theory)

• Temperature: Increasing temperature increases the kinetic energy of molecules, leading to more frequent and energetic collisions.
• Concentration: Higher concentration leads to more frequent collisions.
• Surface Area: Increased surface area (for solids) allows for more contact and collisions.
• Catalyst: Provides an alternative reaction pathway with a lower activation energy, speeding up the reaction.

Le Chatelier’s Principle

• Le Chatelier’s Principle states that if a change of condition (stress) is applied to a system in equilibrium, the system will shift in a direction that relieves the stress.
  • Stressors: Changes in concentration, temperature, pressure (for gaseous reactions).