Chemistry I Final - Second Semester (Chapter 6 - 13?)

Topic List: Metals, Molecules (names and Lewis structures), Molecules (Shape, polarity, resonance, formal charge), Molecules (acids, comparison of ionic and molecular compounds), Chemical change (equations and types of chemical change), Chemical change (activity series & Single replacement reactions), Chemical Change (Double replacement reactions), Counting matter (the mole), counting matter (mass, moles, and particles), mole ratios in compouds, formulas of hydrates, percent compostion, empirical formulas, stoichiometry (mole ratios + mass and mole ratios in chemical change + limiting reactants + percent vs theoretical yield)

kapeesh

atoms form covalent bonds by sharing electrons to become stable

kapeesh?

Covalent Bond

Chemcial bond formed when atoms share electrons

Molecule

formed when 2 or more atoms bond

Diatomic Molecules

exist because 2 atom molecules are more stable than one

ex. H₂, F₂

Dr. H BrONClIF

mnemonic to remember the diatomic molecules (7)

• Hydrogen

• Bromine

• ….

Bonding Pair

what is this called?

Lone Pair

now what about this?

Sigma bond

single covalent bond that occurs occur when the pair of shared electrons is in an area centered between the two atoms

Single Bond

1 sigma bond

Double Bond

form when 2 pairs of electrons are shared between 2 atoms

1 sigma bond + 1 pi bond

Triple Bond

form when 3 pairs of electrons are shared

1 sigma bond + 2 pi bonds

Ich verstehe

NAMING BINARY MOLECULAR COMPOUNDS:

• first element is the entire name

• second element is the root + “ide”

• prefixes of the elements indicate the number of atoms for each element

Verstehst du?

mono-

prefix for 1

di-

prefix for 2

tri-

prefix for 3

tetra-

prefix for 4

penta-

prefix for 5

hexa-

prefix for 6

hepta-

prefix for 7

octa-

prefix for 8

nona-

prefix for 9

deca-

prefix for 10

more; less

the strength of covalent bonds depends on the distance between the nuclei

• ____ distance = ____ strength

Bond dissociation energy

amount of energy required to break a bond

greater

the energy needed to break a bond is _______ when the length is shorter

Endothermic Reaction

more energy is needed to break a bond than is released

Exothermic Reaction

more energy is released breaking the bond than is needed

entiendo

HOW TO MAKE LEWIS STRUCTURES:

• Find valence electron total
  HCL → 1 + 7 = 8

• Put the least electronegative atom in the center (never H)

• Put 2 electrons between the atoms to form a single bond
  H : Cl

• Complete the octet for the outside atoms
  ..
  H : Cl :

  ^..

• If center atom doesn’t have an octet, move electrons to form double or triple bonds as needed

¿lo entiendes?

je comprends

NAMING ACIDS:

• first word is “hydro” - [root] - “ic”

• second word is “acid”

ex. HCL → hydro | chloric | acid

comprendre?

Acids

any substance that releases hydrogen atoms in water

Binary Acids

acid with 2 elements (no oxygen)

Oxyacid

acid with hydrogen and oxyanion

!

NAMING OXYACIDS:

• per-/hypo- + [root] + -ic/-ous + “acid”

• if the oxyanion name ends in “ite”, the oxyacid ends with “ous”

• If the oxyanion name ends in “ate”, the oxyacid ends with “ic”
  ex. HClO₄ → per | chloric | acid

?

Pi Bond

formed when parallel orbitals overlap and share elements

Structural Formula

letter symbols + bonds showing relative positions of atoms

Space Filling Model

what is this picture an example of ???

Lewis Structure

dots or a line symbolizing a single covalent bond

Ball and Stick Model

what is this picture an example of ??

Resonance Structure

more than 1 valid lewis structure for a molecule or ion

• bond lengths are identical to each other

• intermediate between single and double bonds

understando

OCTET RULE EXCEPTIONS:

• NO₂ has 5 valence electrons from N ans 12 from 0

• it can’t form an exact number of electron pairs

understando?

Coordinate Covalent Bonds

1 atom donates both electrons to share with an ion that needs two

expanded octet

3rd group of atoms with >8 valence electrons electrons

• elements in period 3 or higher have d-orbital and can form over 4 covalent bonds

Dipole

uneven charges at the end of a polar bond

Polar Covalent Bonds

uneven sharing of electrons resulting from one element being more electronegative than the other (it attracts more of the electrons to itself)

Solubility

a substances ability to be dissolved

• polar and ionic dissolve in polar

• non polar dissolve in non polar

(like dissolves like)

Van der Waals forces

the weak attraction between molecules

• vary in strength, but are weaker than bonds in ionic compounds

Intermolecular forces

• London dispersion force (van der waals force)

• dipole-dipole

• hydrogen bonding

Dipole-Dipole Interaction

force between 2 oppositely charged ends of 2 polar molecules

Hydrogen Bonding

especially strong dipole-dipole force between H and either F, O, or N atoms on dipoles

O ye mi

PROPERTIES OF COVALENT BONDS:

Physical properties are usually caused by intermolecular forces

• Low melting point

• Low boiling point

• many are soft solids

• crystal lattice, but with less attraction

ṣe o ye ọ?

Covalent Network solids

solids composed of only atoms interconnected by a network of covalent bonds

• Quartz

• Diamond

Chemical Reaction

the rearrangement of atoms to form a new substance

• change in temp

• change in color

• odor/gas

• bubbles forming

Reactants

starting substance

Products

substances formed

Reversible

⇋

precipitate formed

↓

gas formed

↑

aqueous solution

• (aq)

• has 1 or more dissolved substances in water

solid

(s)

liquid

(l)

gas

(g)

Word Equation

what is this?:

aluminum (s) + bromine (l) → aluminum bromine (s)

Skeleton Equations

chemical equations are also called

chemical equation

statements using chemical formulas to show identities and relative amounts of the substance

Coefficient

chemical equation number written in front of a reactant or product to show the lowest whole number ratio of the amounts

Synthesis

2 or more substances react to form a more complex main substance

Decomposition

complex substances breaks down into simple substances

• Requires heat, light, or electricity

Single replacement

atoms of one element replaces another element’s atom in a compound

• strong metals displace weak metals

Double Replacement

When ions exchange between 2 compounds

• acid-base reactions

• produce water, precipitates, or gas

Precipitate

solid product in a reaction

Combustion

Oxygen reacts with a substance and releases heat and light energy

• also technically a synthesis reaction

Solute

dissolved substance

solvent

the most plentiful substance; what the solute is dissolved into

Complete Ionic equations

show all the particles in a solution as they exist

• only written for double displacement reactions

Mole

• SI unit to measure the amount of a substance

• equal to 12g of pure C₁₂ (in terms of how many atoms are in it)

• 6.022 × 10²³

Avogadro’s number

6.022 × 10²³

Molar mass

mass (g) of one mole of any pure substance

• found by adding up the atomic mass of all the elements in the substance

Molar Volume (gas)

volume 1 mol occupies at 0 degrees C and 1.00 atm (pressure)

• 1 mol of gas occupies 22.4 L

Percent Composition

percent by mass of an element in a compound (can be determined by chemical formula)

(Mass of element in 1 mol of a compound / molar mass of compound) * 100

Empirical Formula

compounds smallest whole number mole ratio of the elements

ex. H₂O₂ → HO

can be the same as the molecular formula

Molecular Formula

specifies actual number of atoms of each element in the formula unit of the substance

• whole number multiple of the empirical formula

Hydrate

compound that has a specific number of water molecules bound to its atoms

• ex: Na₂CO₃ ‧ 10H₂O

Anhydrous

hydrous compounds after heating

Stoichiometry

study of quantitative relationship between amount of reactants and products

• chemical reactions stop when a reactant runs out

• based on the law of conservation of mass

• relationships derived from balanced chemical equation

Mole ratio

ratio between the number of moles of any substance in a balanced equation

Number of mole ratios written

n(n - 1)

n = number of species in a chemical reaction

Limiting Reactants

limits the extent of the reaction and determines the amount of product formed

Excess Reactants

unused reactants

rozumim

HOW TO FIND THE LIMITING REACTANT:

Problem: The reaction of chlorine gas with solid phosphorus (P₄) produces solid phosphorus pentachloride. When 22.5 g chlorine reacts with 29.0 g P₄, which reactant is limiting?

• Balance the equation
  10Cl₂(g) + P₄(s) → 4PCl₅(s)

• Convert the gram amounts of both elements into moles
  22.5 × 1 / 70.892 = 0.317
  29 × 1 / 123.7512 = 0.234

• Divide the mol amounts you just found (0.317, 0.234) by the respective coefficients from the balanced equation
  0.317 / 10 = 0.0317
  0.234 / 1 = 0.234

• The lowest number from step 3 is the limiting reactant
  0.0317 < 0.235

  
  chlorine is the limiting reactant

Rozumíte?

Ymmaerraen

HOW TO FIND THE MASS OF THE EXCESS REACTANT:

Equation: 10Cl₂(g) + P₄(s) → 4PCl₅(s)

Limiting Reactant: Chlorine (22.5g = 0.317 mol)

Excess Reactant: Phosphorus (29.0g = 0.234 mol)

• Since we know that chlorine is the limiting reactant, use mole ratios to find out how many moles phosphorus will actually be used
  0.317 mol Cl × 1 mol P₄ / 10 mol Cl₂ = 0.0317 mol P₄

• convert mol to g
  0.0317 mol P₄ × 123.7512 = 3.93

• subtract the amount used with the amount given in total
  29.0 - 3.922 = 25.078

Ymmärrätkö?

Theoretical yeld

maximum amount of a product that can be produced from a given amount of reactant

• if two reactant amounts are given, find the limiting reactant, and then solve

Actual Yield

The amount of a substance actually produced

Percent Yield

actual yield / theoretical yield × 100

Suspension

mixtures containing particles that settle if undisturbed

Colloids

heterogenous mixtures with particles sized 1-100nm (intermediate)

• do not settle out

Brownian movmenet

jerky, random movements of particles in a liquid colloid (from particle collisions)

Tyndall Effect

when dispersed colloid particles scatter light

miscible

two liquids that are soluble in each other are ________

Insoluble

substance that does not dissolve

Immiscible

liquids that can be mixed but then separate are __________