Chemistry 1 Test 3

Includes information on Ch 5: Advanced Theories of Bonding, Ch 6: Composition of Substances and Solutions, and Ch 7: Stoichiometry of Chemical Reactions

What forms molecular bonds between 2 nuclei?

The overlap of atomic orbitals

What are the atomic orbitals?

s,p,d, and f

What is the distribution of the electron density in valence bonds?

Localized

Localized

Restricted to a particular place or part of the body

Sigma (σ) Bonds

Formed by direct head-on overlap of atomic orbitals

Where is electron density located for sigma (σ) bonds?

Between the nucei

1st Way Sigma (σ) Bonds form

2 s orbitals

2nd Way Sigma (σ) Bonds form

a s orbital and a p orbital

3rd Way Sigma (σ) Bonds form

Two p orbitals

Every molecular bond contain what?

1 sigma components

Pi (π)

Formed from the overlap of Unhybridized p or d type orbitals

Unhybridized atomic orbitals

Atomic orbitals that have their original shape and energy

Where is the distribution of electron density for Pi (π) bonds?

Above and below the plane of the bond between atomic nuclei centers

What type of bonds are in a single bond?

ONLY 1 sigma bond

What type of bonds are in a double bond?

1 sigma bond and 1 pi bond

What type of bonds are in a triple bond?

1 sigma bond and 2 pi bonds

Hybridizations

Process of forming new atomic hybrid orbitals from mixing atomic orbitals

What does the number of atomic orbital combine equal?

ALWAYS the number of hybrid orbitals formed

The type of hybridizations that occurs corresponds to what?

The electron-pair geometry of the compound

1st Problem with Lewis Theory

Doesn’t give good numerical predictions for bond strength and bond length

2nd Problem with Lewis Theory

Can’t write a “single” correct structure for many molecules

3rd Problem with Lewis Theory

Doesn’t predict the correct magnetic behavior of molecules

Resonance

Describes molecules whose bonding cannot be represented by a single Lewis structure

Molecular Orbital Theory

Formation of bonding (lower energy) and antibonding* (higher energy)

What do electrons occupy?

molecular orbitals not the atomic orbitals the valence electrons came from

For molecular orbital theory, where is electron density distributed?

Delocalized within the moleculeD

Delocalized

Spread over entire molecule

Antibonding Orbitals

Higher in energy than original atomic orbitals and destabilizes a chemical bond

Why do antibonding orbitals destabilize a chemical bond?

Because if has reduced electron density between the nuclei

Where are antibonding orbitals located?

Outside of the region between 2 nuclei

Bonding Orbitals

Molecular orbitals formed by adding the wave functiond of atomic orbitals

How are antibonding orbitals formed?

By subtracting the eave function of atomic orbitals

Where is the electron of bonding orbitals found?

Between the nuclei, stabilizing the molecule

How is the Sigma (σ) Bonding Molecular Orbital from p orbitals formed?

2 p orbitals on different atoms overlap head-on along the internuclear exis

How is the Sigma (σ) Antibonding Molecular Orbital from p orbitals formed?

2 p orbitals aligned along the internuclear axis combine out of phase

How is the Pi(π) Bonding Molecular Orbital from p orbitals formed?

The side-by-side overlap of 2 p orbitals creates 2 π molecular orbitals

How is the Pi(π) antibonding Molecular Orbital from p orbitals formed?

From the combination of out-of-phase p orbitals

What does Molecular Orbitals theory bond order predict?

Whether or not the molecule of ion exists

If the bond order is zero, what does it mean?

The species doesn’t exist

What is the Formula for MO Bond Order

(Bonding electrons # - Antibonding electrons #)/2

What is the bond order of single bonds?

1

What is the bond order of double bonds?

2

What is the bond order of triple bonds?

3

Molecular Formula

Shows the types and actual numbers of atoms of each element in a molecule

Structural Formula

Shows how atoms are connected in a molecule.

Empirical Formula

Shows the simplest whole- number ratio of atoms of each element in a compound

Percent Composition

the percentage by mass of each element in the compound.

How can the Empirical formula be determined?

From % composition of its constituent elements

1st Step for Determining and Empirical Formula from % Composition

Assume there are 100 g of substance

2nd Step for Determining and Empirical Formula from % Composition

Convert % Composition to mass

3rd Step for Determining and Empirical Formula from % Composition

Convert mass to moles, by dividing mass by molar mass

4th Step for Determining and Empirical Formula from % Composition

Divide by the smallest number of moles

5th Step for Determining and Empirical Formula from % Composition

If not whole numbers multiply until whole

Solution

homogeneous mixture of the solvent & solute.

Solvent

The mixture component present in greatest proportion

Solute

The mixture component present in lower proportion.

Molarity (M)

the moles of solute per one liter of solution.

What is the equation for Molarity?

Moles of Solute/ Volume of solution

What are the units for Molarity?

mol/L

How do you find molarity if your given mol element and solution volume?

Dive mol element by solution volume

How do you find moles for a solid solute?

M (mol/L) x V(L)

How do you find sample mass for a solid solute?

Moles A x formula mass of A (g/mol)

What is the formula for making a solution from a concentrated solution?

C₁V_{1 =} C₂V₂

C₁

original (stock or concentrated solution)

C₂

dilute solution concentration

V₁

amount of stock solution used

V₂

new volume of the diluted solution

What is the formula for mass percentage?

(mass of component/ mass of solution) x 100%

Parts per million

ppm or mg/L

Parts per billion

ppb or μg/L

Law of Conservation of Mass

Total mass of substances after a chemical process is the same as before the process

Total number of reactant atoms=

Total number of product atoms

If polyatomic ions are present as both reactants and products, what do you do?

Balance them as a unit and not as separate elements

1st Step in Writing Net Ionic Equations

Write a balanced molecular equation.

2nd Step in Writing Net Ionic Equations

Dissociate all strong electrolytes

3rd Step in Writing Net Ionic Equations

Cross out anything that remains unchanged from the left side to the right side of the equation.

4th Step in Writing Net Ionic Equations

Write the net ionic equation with the species that remain.

For writing a net ionic equation, what can’t be dissociated?

Gas (g), precipitate (s), and liquid (l)

1st Type of Reaction

Precipitation

2nd Type of Reaction

Acid/Base

3rd Type of Reaction

Oxidation-Reduction (Redox)

Precipitation Reactions

Dissolved substances react to form one (or more) solid products.

Acid-Base Reactions

typically resulting in neutralization to form a salt and water (or a gas).

Oxidation

When a atom or ion loses electrons

Reduction

When a atom or ion gains electrons

Can oxidation occur without reduction?

No, they can’t occur without the other

Oxidation states (Oxidation numbers)

used to keep track of the electron transfer in redox reactions.

Oxidation–reduction (redox) reactions

Involve transfer of electrons

What is the oxidation number of an atom in an elemental substance?

0

What is the oxidation number of an monoatomic ion?

Equal to the ion’s charge

What is the oxidation number of an hydrogen combined with nonmetals?

+1

What is the oxidation number of an hydrogen combined with metals?

-1

What is the oxidation number for most compounds combined with oxygen?

-2