Mole
- 1 mole = 6.022*1023
- Molar Mass: measured in amu's
- 1 water molecule weighing 18 amu's weigh 18 grams per mole
Limiting Reagents
- The limiting reagent is the one that runs out first
- To find the limiting reagent convert the amounts of reagents to moles and then multiply them by the stoichiometric ratios and see which one is the smaller number of moles
Percent composition of compounds
- mass percentage of an element = \(\left(\frac{mass\ of\ element}{mass\ of\ compound}\right)\cdot\ 100\)
Determining formulas of composition
- assuming you know the percent composition of the elements of a compound and you know the molar mass of the substance you can find both the empirical and molecular formula of the compound
- change the percentage sign to grams and find the number of moles of each of the elements. Then divide each elements number of moles by the smallest number. Turn the corresponding numbers into a whole number formula.
Stoichiometric calculations
- A + B produce C + D, how many grams of B will ve needed to combust 20 grams of A?
- grams * mol/gram of A * ratio of B:A * grams/mol of B = grams of B that will be needed to combust 2 grams of A
Molarity vs Molality
- Molarity: is the concentration of a solution expressed as the number of moles of solute per liter of solution
- Molality: is the concentration of a solution that indicates the moles of solute per kilogram of solvent
Water is the Universal Solvent
- water will bind to most things that aren't polar
Electrolytes
- Electrolytes are Disassociated ions
- strong electrolytes disassociate fully into their component ions; (strong acids/bases; salts)
- weak electrolytes: don't disassociate into their component ions
Dilutions
- \(m_1\cdot v_1\ =\ m_2\cdot v_2\)
Acid Base Definitions
- Bronstead-lowry: acids are proton donors; bases are proton acceptors
- Lewis: acids are electron acceptors; bases are electron donors
Hydronium Ions
- Abbreviated as H+
- Acids disassociate
Conjugate Acids
- Every base has a conjugate acid
- Every acid has a conjugate base
PH and POH
- \(PH\ =\ -\log\left[H^+\right]\)
- \(POH\ =\ -\log\left[H^+\right]\)
- \(PH\ +\ POH\ =\ 14\)
Cations and Anions
· Cations: Positively charged
· Anions:Negatively charged
Precipitation Reactions
· 2 aqueous solutions form a precipitate and another aqueous solution
Writing Precipitation Reactions
· Molecular
· Ionic
· Net ionic (only counting ions that lead to the solid precipitate)
Troy ounce
· I troy ounce weighs 31.1 grams
Redox reactions
· Reduction: gains electrons
· Oxidation: loses electrons
Oxidation numbers
· The oxidation number for any element by itself is 0
· Oxidation number of a monatomic ion = charge of the ion
· Oxygen when not in hydrogen peroxide has on oxidation state of -2
· Hydrogen = +1
· Fluorine = -1
· All halogens have an oxidation state of -1 unless bound to hydrogen or fluorine
Naming Ionic compounds
· Cation, Anion
The Ideal Gas Laws
· Boyle’s law; p*v = k
· Jacques Charles; v/t = b
· Amadeo Avogadro; volume/amount of moles = constant
· Ideal gas Law; PV = nRT
The ideal gas law explained
· Pressure is measured in pascals [newton’s/area in meters2] or in atmospheres
· 1ATM is equal to 101325 pascals or 100 kilopascals
· N = amount of moles
· R = universal gas constant [8.3145 lkpa/kmol]
· T = degrees in kelvin
Gas jargon
· STP = 0 degrees Celsius and 100 kilopascals of pressure
· 1 mol of any ideal gas takes up 22.4 liters of space at STP
· Absolute zero; 0 kelivins or -273.15 Celsius
Vander walls Equation
· (P+n2a/v2)(v-nb) = nRT
· b= mass taken by each gass
· a= attraction constant
Rule of partial pressures
· so long as the gases don’t chemically react the total pressure of 2 gases in a container is equal to the sum of the pressure of the 2 gasses
Kinetic Energy
· Ek = ½ mv2
· V = square root of 2 * Ek/m
Effusion
· r = v/t
· ra/rb = sqare root of ma / square root of mb
Change in Energy
· change in energy = q + E
· exothermic = - value of delta E
· endothermic = + value of delta E
Enthalpy
· H = E + PV
· Change in enthalpy = change in heat
· Delta H = q
Standard formations
· T=25 degrees Celsius
· C=278.15 k
· P=1atm
Hess’s law
· Change in enthalpy = sum of the standard enthalpies of the formation of the products – the sum of the standard enthalpies of the reactants
· Delta H = the sum of the number of moles of products time the standard enthalpies of the products – the number of moles of reactants times the sum of the reactants
Calorimetry
· Delta H = the specific heat capacity of the substance times it’s total mass time the change in temperature
· Mass is represented as grams
· Temperature is represented as kelvin
Entropy
· Change in entropy = the sum of the standard entropies of formations of the products time the moles of products – the sum of the standard entropies of formations of the reactants time the moles of reactants
Gibbs free energy
· Delta g = delta h – t time delta entropy
The Speed of Light
· C = wavelength * frequency
· C = 3*108 m/s
· High frequency beams will eject an electron
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