Chemistry (Measurement, Gases, Changes, Chemical Equations, Reactions, Periodic Trends)

Density:

D = m/v

M = mass (grams)

V = volume (mL or cm^3)

1 mL = 1 cm^3

Scientific Notation:

To convert scientific to standard:

Positive exponent - move the decimal to the right the same number of places as the exponent

Ex. 4.3 * 10^3 = 4,300

Negative exponent - move the decimal to the left the same number of places as the exponent

Ex. 8.55 * 10^-1 = 0.855

The number should be less than 10 and greater than 1
To convert back to scientific notation, do the opposite by counting the number of places the decimal point could move

Sols, Nats, Meks (dimensional Analysis):

1 sol = 5 nats

36 sols = 1 dran

12 sols = 1 mek

1 sol = 3 arks

10 arks = 1.20 freds

Significant Figures:

Rules:

Non zero numbers are always significant ex. 72.3 has 3
Zeros between non zero numbers are always significant ex. 60.5 has 3
All final zeros to the right of the decimal place are significant ex. 6.20 has 3
Zeros that act as placeholders are not significant. Convert quantities to scientific notation to remove the placeholder zeros ex. 0.0253 and 4320 each have 3
Counting numbers and defined constants have an infinite number ex. 6 molecules or 60 s = 1 min

Estimating Volume:

Estimate one place more than given

Ideal Gases:

The collision between gas particles and container walls are elastic; there is no loss of kinetic energy. As long as the temperature is constant the KE remains the same
Gas particles overcome attractive forces (hydrogen bonding, dipole-dipole, dispersion) between them, except near the temp at which they condense and become a liquid. Thus, there are no forces of attraction or repulsion between gas particles

Real Gases:

They occupy space and exert attractive forces on each other. Real gases behave like ideal gases at high temp, high volume, and low pressure.

Gas Laws:

Boyle’s Law: Pressure-Volume Relationship

The volume of a fixed mass of gas varies inversely with the pressure at a constant temperature
As V goes up P goes down, vice versa
VP = k
Ex. barometer

Charles’ Law: Volume Temperature Relationship

The volume of a fixed mass of gas at constant pressure varies directly with the Kelvin temperature
As temp goes up, V goes up, vice versa
K = V/T

Gay Lussac’s Law: Pressure-Temperature Relationship

The pressure of a fixed mass of gas at constant volume varies directly with the Kelvin temperature
As temp goes up pressure goes up, vice versa
K = P/T

Combined Gas Laws:

K = PV/T
P1V1/T1 = P2V2/T2

Ideal Gas Law:

K = VP/Tn = k
N = mols
PV = nRT

At STP:

V = 22.4 L
P = 1 atm
T = 273 K
N = 1 mol

Units of Pressure:

760 mmHg = 1 atm = 760 torr = 101.3 kPa

0 degrees celsius = 273 K

Mols:

Mol - unit of measurement used to count atoms

1 mol = 6.02 * 10^23 atoms

Partial Pressure:

The total pressure of a mixture of gases is equal to the sum of the partial pressures of the component gases
Pt = P1 + P2 + P3…
Dalton’s Law of Partial Pressure: Ptotal = Pgas + PH2O

Physical Changes:

Change in state of matter
Change in size
Change in shape
Ex. vaporization, when liquid changes to gas
Mixtures
Evaporating the water
Ex. dissolution, solid “dissaperared”

Chemical Changes:

Substances’ composition has changed
Bonds between atoms are broken
New bonds are formed
Ex. electrolysis, hydrolysis, decomposition, water changes to form two gases
Bonds broken
New substance made
Ex. single replacement reaction, saw a gas form

Average Atomic Mass:

Multiply mass and abundance (move decimal two places to the left) for each isotope
Add all the answers together
Proton - 1.00727 amu
Neutron - 1.00866 amu
Electron - 0.00055 amu

Naming:

Molecular Compounds (nonmetal + nonmetal):

1= mono
2= di
3= tri
4= tetra
5= penta
6= hexa
7= hepta
8= octa
9= nona
10= deca
Mono is only used on the second element, if only one of the first element just leave is normally
Add prefixes to first and second element
Add ide to the second element
Ex. CO = carbon monoxide
Ex. N2O = dinitrogen monoxide

Ionic Compounds (metal + nonmetal):

No prefixes
First element stays the same, second element adds ide
Ex. CaBr = calcium bromide

Acids:

Acids are a compound that produces hydrogen ions when dissolved in water.

Nonoxyacids:

Binary acids
The first element is hydrogen and the second element is a nonmetal
Therefore the name of the acid begins with hydro, then the root of the nonmetal and ends with ic
Ex. HCL = hydrochloric acid

Oxyacids:

Contains a polyatomic ion
The name of the acid begins with the root of the polyatomic ion
Ate = ic
Ite = out
Ex. H2SO4 = sulfuric acid

Reactions:

Combination/Synthesis:

two or more substances combined together to form one larger compound
A + X = AX

Decomposition:

One compound breaks apart into two or more smaller compounds/elements
AX = A + X

Single Replacement Reaction:

The atoms of a pure element switch places with atoms in a compound
Metal atoms witch with metal atoms or nonmetal atoms witch with nonmetal atoms
Positive and positive switch or negative and negative switch
A + BX = AX + B

Double Replacement Reaction:

Two ionic compounds react by switching ions
The cation of one compound switches place with the cation in the other compound
AX + BY = AY + BX

Combustion:

A hydrocarbon reacts with oxygen to form carbon dioxide and water
CXHY + O + CO2 + H2O

Balancing:

Make sure the same number of elements on both sides of the arrow

Periodic Trends:

Reactivity:

Alkali metals’ reactivity increases going down a group because…

Atomic radii gets larger, so valence electrons are further from the nucleus, so valence electrons are more easily lost, so ionic bonds form with other atoms
More energy levels added, so more electrons in between the nucleus and the outer most shell, so these core electrons shield the nucleus from the valence lectron and the valence electron feels less attracted to the nucleus

Metals’ reactivity decreases from left to right because…

It is easier to lose one electron than three
The effective nuclear charge signifies how strong of apull the electrons to the nucleus, the larger the charge the more attractive it is
It is harder to lose the electrons because they have a strong pull to the nucleus
An element that loses its electron easily are more reactive because there are less valence electrons to lose

Non metals’ reactivity decrease going down the group

Atomic Radius:

Radius decreases from left to right because…
As we go across the electrons fill into the same main energy level, so the number of protons increases and the number of shielding electrons stays constant, so the effective nuclear charge increases, which pulls the entire electron configuration closer
Radius increases going down a group because…
As we go down the electrons fill into higher main energy levels, so the number of protons increases and the number of shielding electrons increase, so the effective nuclear charge stays constant, but the valence electrons are in their energy levels farther from the nucleus
In general metals have larger radii

Effective Nuclear Charge:

All electrons are attracted to the nucleus due to the attraction of opposite charges (electric force)
The inner core electrons shield the valence electrons from the full charge of the nucleus
The effective nuclear charge is the amount of positive charge that is effectively attracting the valence electrons in an atom with multiple electrons
Zeff = # of protons - # of shielding electrons

Atomic vs Ionic Radii:

Ionic radii follow the same trends as atomic radii
Cations are smaller than the neutral atom
Anions are larger than the neutral atom
Ionic radii increase going down a group for the same reason atomic radii increase
Ionic radii decrease at first moving left to right because…
All cations in the same row have the electron configuration of the previous noble gas, so more protons exert stronger electrostatic attraction of the same number of electrons
When changing to anions the radius is larger at first before decreasing because…
Anions have the electron configuration of the next noble gas so even though there are more protons there are also more electrons
Decrease in radius moving right is because more protons are attracting the same number of electrons
Ions with the same electron configuration are called isoelectronic
For these ions the radius increases as the atomic number decreases
There are fewer protons attracting the same number of electrons so electron-electron repulsion is stronger and coulombic attraction is weaker so ionic radius is larger

Ionization:

Energy needed to remove an electron from an atom
If the ionization energy is high then it is relatively hard to remove an electron from an atom
Ionization energy increases from left to right because…
As one moves across the radii of atoms get smaller, so the valence electrons get closer to the nucleus, so the valence electrons are more attracted to the nucleus, so it takes more energy to remove an electron
Ionization energy decreases down a group because…
As one moves down the radii of atoms get larger, so the valence electrons get farther from the nucleus, so the valence electrons are less attracted to the nucleus, so it is easier to remove and electron since it takes less energy
In general nonmetals have higher ionization energy

Electronegativity:

The relative tendency of an atom to attract an electron from another atom in a chemical bond
If an atom has a high electronegativity the atom strongly attracts electrons to itself
Electronegativity increases left to right because…
As we go across the radii of atoms get smaller, so valence electrons get closer to the nucleus, so electrons are more attracted to the nucleus
Electronegativity decreases down the group because…
As we go down the radii of atoms get larger, so the valence electrons get farther from the nucleus, so electrons are less attractive to the nucleus
In general nonmetals have a higher electronegativity
Noble gases don’t have any electronegativity values