Comprehensive Chemistry Guide: Properties, Reactions, and Concepts

Posted on Apr 26, 2024 in Chemistry

Chemical Properties

Chemical properties describe the changes that occur during a reaction.

Chemical Changes

Chemical changes involve the formation of new substances when elements or compounds combine.

Physical Changes

Physical changes affect the form or appearance of a substance without altering its chemical composition.

Physical Properties

Physical properties describe the observable characteristics of a substance, such as color, density, and melting point.

Naming Compounds

  1. Write the name of both elements (first element then second).
  2. Change the ending of the second element to -ide.
  3. Place prefixes in front of each element based on the number of atoms present.

Prefixes

  • Mono
  • Di
  • Tri
  • Tetra
  • Penta
  • Hexa
  • Hepta
  • Octa
  • Nona
  • Deca

Isotopes

Isotopes are atoms with the same number of protons but different numbers of neutrons.

Atomic Notation

The atomic number is written as a subscript on the left of the element symbol, and the mass number is written as a superscript on the left of the element symbol.

Periodic Law

The periodic law states that elements, when listed in order of their atomic numbers, fall into recurring groups with similar properties.

Element Families

  • Nonmetals: 1, 6, 7, 8, 15, 16, 34
  • Metalloids: 5, 14, 32, 33, 51, 52, 84
  • Transition metals: 21-30, 39-48, 72-80, 104-112
  • Alkali earth metals: 4, 12, 20, 38, 56, 88
  • Alkali metals: 3, 11, 19, 37, 55, 87
  • Halogens: 9, 17, 35, 53, 85, 117
  • Noble gases: 2, 20, 28, 36, 54, 86, 118

Phases of Matter

  • Solid
  • Liquid
  • Gas

Changes of State

  • Solid → Liquid = Melting
  • Liquid → Gas = Evaporation
  • Liquid → Solid = Freezing
  • Gas → Liquid = Condensation
  • Gas → Solid = Deposition
  • Solid → Gas = Sublimation

Trends in Electronegativity

Electronegativity increases as you move from left to right across a period and decreases as you move down a group.

Balancing Reactions

  1. Write the unbalanced chemical equation.
  2. Make a list of the atoms in each element.
  3. Multiply the number of atoms in each element.
  4. Place coefficients in front of molecules.
  5. Check the equation.
  6. Write the balanced chemical equation.

Single Replacement Reactions

AB(aq) + C → A + CB(aq)

Double Replacement Reactions

AB + CD → AD + CB

Net Ionic Equations

Net ionic equations show only the ions that are directly involved in the chemical reaction.

Spectator Ions

Spectator ions are ions that do not participate in the chemical reaction and are found in solution both before and after the reaction.

Polar Bonds

Polar bonds have an unequal distribution of charge between the two atoms.

Polar Molecules

Polar molecules have an asymmetric distribution of charge.

Nuclear Reactions

Nuclear reactions involve collisions between atomic nuclei or between an atomic nucleus and a subatomic particle.

Properties of Acids

  • Sour taste
  • Electrolytes
  • Corrosive
  • pH less than 7
  • Turn blue litmus red
  • Conduct electricity

Properties of Bases

  • Bitter taste
  • Slippery/soapy feeling
  • pH more than 7
  • Turn red litmus blue

Valence Electrons

Valence electrons are the electrons in the outermost shell of an atom.

Electron Configuration for Atoms

Write the energy level (period), then the subshell to be filled, and the superscript (number of electrons in that subshell).

Electron Configuration for Ions

:

first identify the configuration for the neutral atom. Then, add or remove electrons depending on the ion’s charge


Dot structures:

diagrams that represent the valence electrons of atoms within a molecule.

Names of shapes for dot structures:

Linear: 180° bond angles.

Trigonal Planar: 120° bond angles.

Tetrahedral: ≈109.5° bond angles.

Trigonal Bipyramidal: 90° & 120° bond angles.

Octahedral: 90° bond angles.

Hydrogen bonds:

forms a special type of dipole-dipole attraction when a hydrogen atom bonded to a strongly electronegative atom exists in the vicinity of another electronegative atom with a lone pair of electrons.

Solubility:

degree to which a substance dissolves in a solvent to make a solution (usually expressed as grams of solute per liter of solvent)

How temp affects solubility:

Increasing temperature results in increased kinetic energy

How pressure affects solubility:

At low pressure, a gas has a low solubility

Ideal gasses: 

one for which both the volume of molecules and forces between the molecules are so small that they have no effect on the behavior of the gas.

Name of hydrocarbons: 

  • Pick the longest chain for base name
  • Number it to figure out where the side chain is 

Name endings:

2. ethane                           7. heptane                   12. Dodecane

3. propane                         8. Octane   

4. butane                            9. Nonene 

5.  pentane                       10. Decane 

6. Hexane                          11. Undecane

Organic functional groups:

Hydroxyl, methyl, carbonyl, carboxyl, amino, phosphate and sulfhydryl

Isomers:

Isomers are two (or more) molecules that share the same molecular formula.

Metric conversions: 

kilo = k = 1000 or 103        Mili = m = 10-3        Nano = n= 10-9

centi = cm = 0.01 or 10-2    Micro = µ = 10-6  


Significant figures:

Rules: 1. all non zero digits are significant 2. all interior zero’s between two non zero digits are significant 3. trailing zeros after decimal place are significant 4. trailing zero’s before the decimal place are significant 5. leading zero’s before the first non zero digits are NOT significant 6. avoid trailing zero’s before an implied decimal place.

multiplying/dividing rule: the result of calculation carries the same number of sig figs as the factor with the least amount of sig figs.

add/subtract rule: the result of calculation carries the same number of sig figs as the factor with the least amount of sig figs.

Density:

D=m/v

Mole calculations:

divide the given weight of the substance by it’s molar mass

Molar mass for molecules:

g/mol

Nuclear half life: 

T=t/n,

T is the length of a half-life, t is how much time has passed, n is the number of half-lives that have passed.

Mass percent:

mass/ Total mass X 100

Molarity: 

M= n/v 

M= molar concentration n= moles of solute v= liters of solution 

Dilution: 

M1V1 = M2 V2

M1= initial molarity   V1= initial volume in L

M2= final molarity     V2= final volume in L

Ideal gas equation: 

PV=nRT

P= pressure    V=volume     n= amount of substance 

R= ideal gas constant   T= temperature 

Combined gas law: 

P1V1 / T1 = P2 V2 / T2

P1 = 1st pressure    P2= 2nd pressure    

 V1 = 1st volume     V2 = 2nd volume 

T1 = 1st temp.        T2 = 2nd temp


Percent Composition:

mass %= mass/ total mass X 100

Empirical formula:

1. Making use of the molar mass from the PTOE, change the mass of every element to moles  2. divide every mole value by the lowest # of moles computed 3. round to the nearest whole #. this is denoted by subscripts in the empirical formula & is the mole ratio of the elements.

ex. C8 H6 O4 (divide by 2) –> C2 H3 O2  (simplify till it can’t be anymore)