General Chemistry/Useful Equations

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General[edit]

Density \frac{mass}{volume}
Moles \frac{given~mass~(g)}{gram~formula~mass}
Percent Error \frac{measured - accepted}{accepted} \times 100%
Percent Composition (by mass) \frac{mass~of~part}{mass~of~whole} \times 100%
Molarity \frac{moles~of~solute}{volume~of~solution}
Molality \frac{moles~of~solute}{mass~of~solvent~in~kg}

De,broglies law ¥ = h/mv

Atomic Structure[edit]

Symbol Meaning Symbol Meaning
E energy c speed of light
v frequency \lambda wavelength
Q charge r distance
k_e Coulomb's constant h Plank's constant
Energy of Wave E = h v
Wave Relation c = \lambda v
Coulomb's Law F_e = k_e\frac{Q_1Q_2}{r^2}

Solutions, Liquids, and Gases[edit]

Symbol Meaning
P pressure
V volume
n number of moles
T temperature (in Kelvin)
K_f molal freezing point constant
K_b molal boiling point constant
\chi mole fraction
m molality
M molarity


Rauolt's Law P_{solution} = P_{1} \chi_{1} + P_{2} \chi_{2} + \dots
Boiling Point Elevation \Delta T_{solution} = K_b \cdot m_{solute}
Freezing Point Depression \Delta T_{solution} = K_f \cdot m_{solute}
Ideal Gas Law PV = nRT
Combined Gas Law \frac{P_1 V_1}{n_1 T_1} = \frac{P_2 V_2}{n_2 T_2}
Titration M_A V_A = M_B V_B
Dilution M_1 V_1 = M_2 V_2

Equilibrium[edit]

Symbol Meaning
K_{eq} equilibrium constant (general)
K_p pressure equilibrium constant
K_c concentration equilibrium constant
R gas law constant
T temperature (in Kelvin)
\Delta n moles of product – moles of reactant
pH \mathrm{pH} = - \log{[\mathrm{H^+}]}
pOH \mathrm{pOH} = - \log{[\mathrm{OH^-}]}
(for water) \mathrm{pH} + \mathrm{pOH} = 14
Pressure/Concentration K_p = K_c(RT)^{\Delta n}
Equilibrium,
for a reaction a\mathrm{A} + b\mathrm{B} \rightarrow c\mathrm{C} + d\mathrm{D}
K_{eq} = \frac{[\mathrm{C}]^c [\mathrm{D}]^d}{[\mathrm{A}]^a [\mathrm{B}]^b}

Thermochemistry[edit]

Symbol Meaning
q heat energy
m mass
s specific heat
T temperature (in Kelvin)
Heat Transfer q = m c \Delta T
Enthalpy \Delta H = H_{products} - H_{reactants}
Entropy \Delta S = S_{products} - S_{reactants}
Free Energy \Delta G = \Delta H - T \Delta S