Maahi's Chemistry Connections

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Thermochemistry

Chemical reactions that involve transfer of heat between system and surroundings

Endothermic

More heat energy is added than what is released

Bond breaking

Exothermic

Bond making

More heat energy is released than what is added

Standard Enthalpy Change

Neutralization

enthalpy change when a strong acid and base react together to form one mole of water under standard conditions

1. Calculate the number of moles of acid and base using n=cv 2. Determine the limiting reactant 3. Add the volumes of acid and base together (where 1cm^3=1g) to get the mass 4. Use Q=mc∆T to calculate enthalpy change 5. Use ∆H=Q/n

Chemical Bonding and Structure

Bond Strength

measure of energy required to break bond

Bond Length

measure of the distance between two bonded nuclei

Covalent Structures

nonmetals (0 ≤ ΔEN ≥ 1.7)

Ionic Bonding

metals and nonmetals (ΔEN ≥ 1.8)

Hybridization

formed when two atomic orbitals, each containing one electron, overlap to from a new combined orbital

Vespr Theory: used to predict 3D molecular geometry based on the atoms/ions valence shell electron bond pairs

Molecular Polarity

partial charge distribution of atoms in a compound is uneven which is dependent on individual molecular geometry and symmetry

Intermolecular Forces

forces that exist between molecules London Dispersion Forces → all molecules(polar/nonpolar) Dipole-Dipole/Hydrogen Bonding → polar

Periodicity

Non-Metals

gain electrons in reactions (anions)

Metals

lose electrons in reactions (cations)

Periodic Trends

Melting and Boiling Point

Decreases down a group/ Increases across a period until group 14 and then decreases

Electronegativity

Atomic Radius

Increases down a group/ Decreases across a period

Ionization Energy/ Electron Affinity

Decreases down a group/ Increases across a period

Atomic Structure

Standard Notation

Orbital

Each orbital has a specific energy level, with 1s being the lowest energy level

Hund's Rule: orbitals of same sublevel are filled singly, then paired up Aufbau Principle: electrons are added to lowest energy level first Pauli Exclusion Principle: no more than two electrons per orbital and they must spin oppositely

Electron Configuration

Ionization energy: minimum energy required to remove an electron from a neutral gaseous atom/moleule in its ground state x^(n-1)(g) → x^n+(g) + e⁻

Stoichiometry Relationships

Isotopes: atoms of the same element with different mass numbers, but similar chemical properties

Mass spectrometer

Titrations: technique where solutions of known concentration is used to determine concentration of unknown solution (n=CV)

Limiting Reactant: the first reactant to be consumed completely in a chemical reaction Excess Reactant: the reactant that could keep reacting if limiting reactant had not been done

Mole Concept

Avogadro's Constant 6.02×10²³ objects/mol⁻¹

Molar Mass (g/mol)

M=m/n

Mole (mol)

n=m/M

n=N/L

Measurement and Data Processing

Accuracy

Systematic Errors: Flaw in the actual experimental design, defect with instrument or the way the measurement was taken

Precision

Random Errors: Uncontrolled variables in an experiment

Scientific Notation: used to make numbers and quantities easier to comprehend and write

Significant Figures: the number of digits reflecting the precision of a given measurement

Graphing Techniques

Lab Equipment

Maahi's Chemistry Connections