Chemistry 30: Chemistry 20 review

Ions

Atoms that gain or lose electrons to have an overall electrical charge

Cations

-Positive charged ions beacuse they lose electrons

-formed from metals

Anions (-)

Negative charged ions because they gain electrons

-formed from non metals

-...ide ion

What does the group number represent

The group number equals the number of electrons in valence shells and that will help predict number of electrons an atom will gain or lose

chemical compound

Contains two or more elements combined in fixed proportions and held together by chemical bonds which results from the force of attraction between atoms

molecular compound

-compounds formed between non metals atoms only

-elements share electrons to form a covalent bond

Diatomic elements

Some elements do not exist naturally as single atoms (unstable) and exist as molecules of two or more identical atoms

Ionic compounds

Compounds formed between a metal and a non-metal atom

-atoms transfer electrons creating ions that are held together in ionic bonds

Multivalent ionic compounds

- compounds that contain elements whose ions can take on more than one charge

-roman numerals are used to indicate the charge of the ion

evidence of chemical reaction (5)

- colour change

-odour change

-formation of gas

-formation of precipitate

-energy change

Conservation of mass

Mass of reactants= mass of products

Formation reaction

A+B---->AB

Single Replacement

A + BC --> B + AC

Double Replacement

AB + CD = AD + CB

Hydrocarbon Combustion

CH4+O2-----> CO2+H2O

mole (mol)

The mole is defined as the number of carbon atoms in exactly 12g of pure carbons

Molar mass =

The mass of one mole of an element, molecular compound, or an ionic compound

-g/mol

Mole ratio

In a balanced equation, the ratio between the numbers of moles of any two substances

amount (n)

Number of moles (mol) of substance present in any given mass

Types of experimental errors

1) Instrumental errors- instrument is only precise to half its smallest scale

2) chemical purity

3) side reactions

4)qualitative judgements

5) loss of solid during filtaration

%yield

Actual yield/ theoretical yield *100%

Limiting reagent

The reactant which limits the amount of product produced

Excess reagent

the reactant that is not completely used up in a reaction

Chemical bond

Hold entities together

intramolecular forces

Is the force within a molecule holding atoms together

-strength influences chemical reactivity

intermolecular forces

forces of attraction between molecules

-strength influences boiling and melting points

valence electrons

Electrons on the outermost energy level of an atom

-only valence electrons are involved in bonding and chemical reactions

Electronegativity

A measure of the ability of an atom in a chemical compound to attract electrons

What element has the highest electronegativity

Fluorine (4.0)

What element has the lowest electronegativity

Francium

Electronegativity and reactivity trend

-increases left to right

-bottom to top

Bonding

The electronegativites of atoms determine what type of bonding occurs between them as each atom will try to attract the bonding electrons toward itself

covalent bond

-between atoms with relatively high electronegativites

-covalent bond is defined as the simultaneous attraction of the two nuclei for the shared pair of the bonding electrons

-non-polar 0.0

-polar: 0

ionic bond

-significant difference in electronegativites

-ionic bond which is defined as the force of attraction between a cation and an anion

-EN>1.7

Metallic bonding

-between atoms with realitievlh low electronegativites

- metallic bond is defined as the simulataneous attraction between positive nuclei and mobile valene electrons in a metal

-EN varies

Covalent network bonding (diamond)

- a 3-D arrangement of atoms continuously linked throughout the crystal by strong covalent bonds

-most involve carbor or silicon

Bonding continum

Weakest: ionic, polar covalent, nonpolar covalent, network covalent- strongest

The period number

The number of energy levels= the period number of the element

The group number

Group number= number of valence electrons in an atom

Orbital

a region in an atom where there is a high probability of finding electrons

octet rule

every atom wants to have eight valence electrons in its outermost electron shell. When four valence orbitals are completely filled with electrons, the atom assumes the stable electron configuration of a nobel gas

bonding electrons

Unpaired electrons in the valence shells that are available for bonding

lone pair

Paired electrons that are unavailable for bonding

Lewis diagram

The method of showing the organization of the valence electrons in an atom

Sterochemistry (VSEPR)

The study of the 3-D shape of the molecules and ions and how this affects their reaction

VSEPR theory

valence shell electron pair repulsion theory

-the theory requires that the number of valence electrons be known

-shape of molecules can be determined from lewis diagram

-electron pairs try to push each other as far away as possible while still bonding to the central atom

Non-polar covalent bond

Equal sharing of bonding electrons

-formed between like atoms or atoms with the same electronegativity

-EN=0.0

polar covalent bond

A covalent bond in which electrons are not shared equally

-unlike atoms

-bond dipole: when there is an electronegativity difference between 2 bonded atoms (0

Non-polar Molecule

If a molecule has bond dipoles and it is symmetrical, all the dipoles cancel out and the molecule will be non polar

polar molecule

A molecule that has electrically charged areas.

-unsymmetrical

intramolecular bonds

-attraction between atoms within a molecule

-strong bonds

-ionic

-polar covalent

-non-polar covalent

-network covalent

Intermolecular bond

-attraction between molecules

-affects physical properties----these forces must be overcome in order for phase change to occur

-weak forces

What are three types of intermolecular forces

-london dispersion forces

-dipole-dipole

-hydrogen bond

London Dispersion Forces

are a type of force acting between atoms and molecules.

-weak forces

-results from the random movement of electrons in molecules

-creates a temporary dipole

-all molecules have LD forces

What 2 factors influence LD forces strength

1) the number of electrons------ more electrons, the stronger the forces

2) the shape of molecule---- the stronger the molecules can get to each other, the stronger the attraction

Dipole-Dipole

-polar molecules

hydrogen bond

-when a hydrogen atom is bonded directly to a very electronegative atom such as F,O,N

-the large difference in electronegativites between hydrogen and the other atom produce highly polar bonds

-strongest of all intermolecualr bonds

Boiling and melting points

-the greater the intermolecular bond strength between the molecules of a compound, the higher the melting and boiling points

-this is due to the increased energy which must be supplied to break the strong intermolecular bonds between the molecules

crystal lattice

the regular pattern in which a crystal is arranged

-ions in ionic compounds pack together very closely to arrange themselves in repeating 3-D patterns

-an empirical formula shows the simplest whole number ratio of ions in ionic compounds

Properties of ionic compounds

-hard, solid, and brittle

-high boiling and melting points

- liquida and solutions conduct electricity

Physical properties of metallic compounds

-shiny, silvery

-flexible, maeable, and ductile

-electrical conductivity

-crystalline

4 properties of gases

-highly compressible

-diffuse into free spaces

-move rapidly in constant motion

-always fill their container

4 variables that describe a gas

-volume (L)

-temperature (K)

-pressure (atm or kpa)

-amount (mol)

Relationship between the amount of gas and pressure

-the higher the amount the particles, the higher the pressure due to increased collisions

Volume of a gas and pressure

-as volune decreases, the pressure increases

Temperature and pressure

-higher the temperature, the higher the pressure

What is temperature measured in

Kelvins

(273.15)

Boyles law

P1V1=P2V2

-as the pressure of a gas changes, the volume varies inversely

Charles law

-volume of a gas is directly proportional to its temperature

-v1/T1= v2/T2

What is the combined gas law?

P1V1/T1=P2V2/T2

Kinetic Molecular Theory (KMT)

It is a model to explain the behavior of gaseous particles

-if a gas follows all the points of KMT, it is said to be ideal

What are 4 points of KMT

1) particles are in constant, random, straight line movement

2) the volume of gas particles is negligible beacuse particles are far apart

3) gas particles do not attract or repel

4) kinetic energy is proportional to the temperature

Molar volume of a gas

Units: l/ mol

STP: 22.4 L/mol

SATP 24.8 L/mol

molar volume meaning

- 1 mol of a gas occupies a certain volume at a specific temperature and pressure

- and SAT AND SATP, any gas will occupy the volume of 24.8 or 22.4 L/mol

Solute

Substance that is dissolved (smaller amount)

Solvent

Substance doing the dissolving (larger amounts)

non-electrolyte

a compound that dissolves in water (aqueous) but does not conduct electricity

Ex) sugar

-molecular compounds

Electrolytes

compounds that conduct electricity when melted or dissolved in water

-ionic compounds

-strong acids

Dissociate

Separation of ions that occur when an ionic compound dissolve in water

-individual ions dissociate

-electrolyte

Ionization

-the proccess by which a neutral atom or molecule is converted into ions

-acids

-electrolytes

6 strong acids

-HCl hydrochloric acid

-HI. Hydroiodic acid

-HBr hydrobromic acid

-H2SO4 sulfuric acid

-HClO4 perchloric acid

-HNO3 nitric acid

Flame test

- when a substance is burned either as a solid or in solution, the flame will turn a specific color based on the ions present

Endothermic

-uses energy

-breaking bonds

Exothermic

-forming bonds

-releases energy

Concentration

ratio of solute to solvent in a solution

dilute solution

A mixture that has only a little solute dissolved in it per unit volume

concentrated solution

A mixture that has a lot of solute dissolved in it per unit volume

% concentration units

% by volume ml/100ml

% by mass g/100g

% mass by volume g/100ml

Molar concentration

-mol/l

ion concentration

In solutions of ionic compounds, ions are expressed in mol/L

Dilution Formula

C1V1=C2V2

C1= initial concentration

C2= final concentration

V1= initial volume

V2= final volume

Solubility

-measure of the maximum amount of solute you can dissolve at a specific temperature

-mol/L

-g/100ml

saturated solution

a solution that cannot dissolve any more solute under the given conditions

-if you add more solute, it will settle at the bottom

unsaturated solution

Any solution that can dissolve more solute at a given temperature

supersaturated solution

contains more dissolved solute than a saturated solution at the same temperature

-formed by heating the solution

factors affecting solubility

1) temperature

2) pressure

3) polarity

How does temperature affect solubility

as temperature increases:

-solubility of solids increase

-solubility of gases decrease

Polarity

"Like dissolves like"

-polar solutes dissolve in polar solvents

dynamic equilibrium

continuous movement, but no overall concentration change

-rate of dissolving= the rate of crystallization

-double arrows are used to represent dynamic equillibrium

Spectator ions

Ions that do not participate in the reaction