AP Chemistry (Labaratory Skills (When pouring, pour gently but don't…
When pouring, pour gently but don't speed up or slow down.
Waft to smell; no sniffing
Always wear goggles (and apron if instructed)
Add acid to water, to prevent any dangerous splashes.
Do experiments that release toxic gases in the fume hood
Include:Intro, materials, Procedure, MSDS, purpose, objective, data tables, analysis, error analysis, conclusion
Acids and Bases
: Under Bronsted-Lowry (B-L) definition, bases accept protons(H+) and acids donate protons. Under the Lewis definition(L), bases donate electron pairs and acids accept electron pairs. Under the Arrhenius definition, bases increase [OH-] and acids increase [H3O+] or [H+]. All definitions are true. Strong acids are weak bases and strong bases are weak acids.
(hydrochloric acid, hydrobromic acid, hydroiodic acid, sulfuric acid, nitric acid, perchloric acid): dissociate completely(or almost completely) in solution
(acetic acid): barely dissociate in solution
(sodium hydroxide, potassium hydroxide, lithium hydroxide, barium hydroxide): accepts protons readily(B-L), donates electron pair(Lewis), and the OH- concentration is increased.
(ammonia): forward and reverse dissociation reaction
:Formed by the cations and anions that are part of acids and bases(not H+ or OH-), which can act as weak acids/strong base counterions/conjugate acids/small highly charged metals, and weak bases, respectively, are in solution in the water that is also produced in the neutralization
pH = -log[H+ or H3O+], pH +pOH = 14
For strong Acids concentration of acid equals concentration of H+ or H3O+
For weak acids make an ICE table, using the acid's concentration to find x, which is the H3O+ concentration. Afterwards, use the previous pH formula
H2O to H3O+ ionization (self ionizing) is ignored because it's insignificant
: In a reversible reaction, equilibrium is reached when there is no change in the concentrations of reactants or products.
: The ratio of concentration of products to concentration of reactants at equilibrium.
= ([C]^c [D]^d )/([A]^a [B]^b)
When aA+bB<-->cC+dD in a reversible reaction (exclude solids and liquids)
Le Châtelier's Principle
: if a reversible reaction at chemical equilibrium is disturbed, the reaction will move to counteract that disturbance and therefor bring the reaction to equilibrium again.
: The ratio of concentration of products to concentration of reactants
= ([C]^c [D]^d )/([A]^a [B]^b)
When aA+bB<-->cC+dD in a reversible reaction
, the reaction will
move to the right
, or be
skewed towards the products
, the reaction is at
, the reaction will
move to the left
, or be
skewed towards the reactants
Make a table with initial concentration, change of concentration (with a variable), and equilibrium concentration for each element, given Keq value. Then, plug into the Keq equation and solve for x and subsequently whatever the problem asks for.
Types of reactions
Combustion: A hydrocarbon combusts with oxygen and produces carbon dioxide and water.
CXHYOZ + O2-->HO2 +CO2
Single Replacements:A cation replaces a cation in an ionic compound OR an anion replaces an anion in an ionic compound.
Decomposition: One compound splits into two or more compounds or elements.
Double Replacements: A cation in an ionic compound replaces a cation in an ionic compound, OR a anion in an ionic compound replaces a anion in an ionic compound
Synthesis: two or more elements/compounds combine into one compound.
Acid Base Reactions
Acid and base neutralize to form water and a salt.
Example: HCl +NaOH--> H2O+NaCl
Aqueous ionic compounds are written with aq ions. Ions are cancelled from both sides(spectator ions). The remaining equation is net ionic.
Bonding: Atoms bond to become more stable
: Transfer of electrons from metals to nonmetals, creating a difference in charge and electromagnetic attraction that creates the bond.
Metallic: Positively charged ion and sea of electrons.
: Non-metal to non-metal. Elements share electrons. Network covalent bonds are covalent bonds that are intermolecular bonds. Covalent network structures are made from a network of repeating lattices of covalently bonded atoms. In polar bonds, more electronegative ions "want" the ions more, so they take the ions more. In nonpolar bonds, they're shared equally.
Rate Law: mathematical expression that relates reaction rate to [reactant]. The data is found experimentally.
rate = k[A]^x[B]^y
A and B are the values for reactants and x and y are the order (similar to importance) of the reactants.
k is the rate constant (calculated by solving for it if other components of the rate law are known.)
Overall reaction order=x+y
The order can be calculated when the other reactants are constant and only one reactant(A) is changed. If the rate stays the same, the order is 0. If the rate multiplied by the factor [A] was increased, the order is one. If the order is two, the factor [A] was increased by squared can describe the change in rate.
Method of Initial Rates
When given a table with initial values of the reactants and rates at a specific time, you can calculate the x and y values by comparing the change in reactants to the change in rate. K can also be calculated by using 1 row in the table's values, plugging them in, and solving for k.
: An arrangement of all the known atoms that organize into group and family. Each group shares properties.
: Using the periodic table, we can figure out the electron configuration of each element's basic atoms. We can also find the electron configuration of ions that these atoms can form. The valence shell of the atom, if more than half full, will try to gain a certain number of electrons to make a full octet shell. If the valence shell of the atom is less than half full, it will try to get rid of that certain amount of electrons to eliminate the outermost valence shell.
: how much the atom wants to attract an electron to be negatively ionized. This goes up as we go up and to the right on the periodic table. This is because atoms on the left of the periodic table want to give away electrons to be positively charged rather than to gain an electron. As you go down a group, the electronegativity decreases because the distance between the nucleus and electrons increase, decreasing the electromagnetic attraction
: Electron affinity is the amount of energy spent or gained when a neutral atom is ionized negatively. This has a similar trend to electronegativity because it releases more energy to negatively charge a very electronegative atom and takes energy to negatively charge an atom that wants to give away electrons rather than absorb them.
: the amount of energy required to take away an electron from. It gets higher as you go up and to the right on the periodic table. It gets higher as it goes to the right because atoms want to gain electrons towards the right of the periodic table to get to a full valence shell. Towards the top of the table, the negatively charged electrons are closer to the positively charged nucleus, so the electromagnetic attraction is higher, and therefore, it's harder to pull away an electron from smaller atoms.
: The radius of an atom. The radius of an atom gets higher as you go down a group and to the left. This is because as you go down, you add an energy level, which adds to the radius. As you go to the right, the number of protons increases, so electromagnetic attraction increases as well, making the atom smaller, which is why the radius is higher on the left side.
All Free elements: 0
Group 1: +1
All Monoatomic ions: charge of ion
Group 2: +2
Hydrogen = +1, except in hydride(-1)
Zn or Cd= +2
Al or Ga=+3
The sum of all oxidation states in a compound is equal to its overall charge
All of the rest are in other ions
Identify which oxidation numbers of elements are changed, which oxidized and which reduced.
Split the reaction into oxidation and reduction half-reactions.
Balance atoms that aren't hydrogen or oxygen first(normal balancing)
Add H+ to the hydrogen deficient side on both half reactions
Ad H2O to the oxygen deficient side on both half reactions.
Balance charge by adding electrons
Equalize the electrons transferred by multiplying the entire half-reactions by integers.
Add the two reactions together, and cancel terms that are on both sides.
IF the reaction is basic, add an OH- to both sides for each H+, and repeat the previous step. Combine H= and Oh- to make H2O, if applicable.
: The molar ratio that the elements in a compound are in. The
is the actual composition.
: When given mass percentages, you assume it's 100g, so if 22.4% is given, you would make it 22.4g. Then, convert to moles with molar mass for all the elements. Then, divide all the mole amounts by the smallest number of moles out of all the elements. The resulting numbers will be the empirical formula. Multiply them all by a certain number to make them all integers.
: In a combustion of a compound, we are supposed to find the empirical formula given the products(water and carbon dioxide) yields. Once we find the moles of products, we can use stoichiometry to find the amount of carbon and hydrogen in our desired compound. IF there is a third element, we can subtract the total grams of our carbon and hydrogen to find the grams of the third element, which we can use to find moles. Then, divide by the smallest mole amount and you have your empirical formula. Then, multiply by a number that makes the ratio in integers.
1s^2 : Here, the 1 stands for the energy level, the s signifies the s-block orbital, and the 2 signifies the number of electrons.
: Electron orbitals are probability maps for the location of electrons in the shells of an atom. Each orbital can hold two electrons. There are 4 types of orbitals,
s, p, d, and f
: An atom's last electron is given quantum number, and there are four of them.
Principal quantum number
: Shows which energy level the electron is in.
: An electron occupies the lowest energy level's orbitals first.
Angular momentum quantum number
: Indicates which type of orbital it is.
Magnetic Quantum number
: The orientation of the orbital. The s orbital has 1 orientation, the p block has 3 orientations, the d block has 5 orientations, and the f block has 7 orientations.
Pauli Exclusion Principle
: Each orbital can only hold two electrons
Spin quantum number
: Indicates which way the electron is
: If there are two or more vacant orbitals of the same energy level and type, each will accept one electron (all same spin) before they start filling with electrons spinning in the opposite direction.
: The outermost energy level/ shell of electrons
: the most dense part of an atom, containing neutral neutrons and positively charged protons. The electrons orbit around the nucleus, and have a charge of -1
: A proton splits into a positively charged beta particle (positron) and a neutron, and the positron is ejected for a net 1- charge
: a neutron splits into a proton and a beta particle (with 1- charge), and the beta particle is expelled from the nucleus, making this process have a net 1+ charge.
: a form of radioactive decay in which a neutron is ejected.
: The nucleus emits an alpha particle, which is composed of two protons and two neutrons. the net charge of this process is 2-.
: the emission of gamma waves, which is just emission of energy in wave form.
: an atom with a different number of neutrons than another isotope. Isotopes have different forms of decay and different properties, including mass.
Acids and Bases ||
Calculate pH with salt
:In the salt, which ever ion acts as the stronger base/acid, that reacts with water to form the conjugate and H+ or OH-. Then do ICE tables with the concentration of the ion to find x, the value of the H+/OH- formula. Then calculate the pH using pH formulas