## Chemistry Essentials

#### Some Basic Concepts

↦ 1 mole = 6.02 * 1023 particles = 1g. atom or 1 g molecule

↦ NA = 6.02 * 1023

↦ 1 a.m.u = 1/6.02 * 1023g

↦ Equivalent mass = atomic mass/valence factor

↦ Average atomic mass = (Isotopic mass(A)*percentage + Isotopic mass(B)*percentage)/100

↦ Molarity (M) = nsolute / Vol. of solution(L)

↦ Molarity (m) = nsolute / mass of solvent(kg)

↦ Normality (N) = no. of gram equivalents / vol. of solution(L)

↦ mole fraction = XA - nA/(nA+nB)

↦ Atomic mass = Equivalent mass * Valency

↦ Dilution formula : M1V1 = M2V2

↦ One mole is the amount of substance which contains Avogadro's Number of particles (Avogadro's number is NA = 6.02 * 1023)

↦ One mole of any substance has a mass equal to the formula weight of the substance in grams. (The formula weight of a substance expressed in grams is called its "molar mass.")

↦ One mole of any gas at standard temperature and pressure (STP:0°C, 1 Atm) occupies 22.4 L of volume. (22.4 L is called a "Standard Molar Volume.")

↦ To find the number of moles in some mass of a substance (an amount of substance in grams): Divide the mass of substance by the molar mass (formula weight in grams): Mol = mass/FW

↦To find the mass (amount of substance in grams) given some number of moles a substance: Multiply the moles of substance by the molar mass (formula weight in grams) Mass = mol * FW

#### Atomic Structure

↦ E = hv =hc/λ

↦ hv = hv0 + K.E.(Photoelectric effect)

↦ rn = a0 * n2/z (a0 = 52.9m)

↦ En = -(z2/n2) * 2.18 *10-18 J

↦ v‾ = RH * z2[1/n21 - 1/n22]

↦ de-Broglie equation = λ = h/mV

↦ Heisenberg uncertainty principle : Δx > Δp ≥ h/4π

↦ Number of orbitals in a shell = n2

↦ Number of electrons in a shell = 2n2

↦ Number of radial nodes = (n – l – 1)

#### Chemical Bonding

↦ H = 1/2[V + X - C + A] (H = number of Hybrid orbitals)

↦ Bond order = 1/2[Nb - Na]

#### States of matter

↦ Boyle's law : P1V1 = P2V2

↦ Charles law : V1/T1 = V2/T2

↦ Ideal gas equation : PV = nRT

↦ Dalton's law : PTotal = P1 + P2 + P3 + ......

↦ dgas = PM/RT

↦ Graham's Law: r1/r2 = √(M2/M1)

↦ Vander waal's equation : (P + an2/v2)(v-nb) = nRT

↦ CP - CV = nRT

↦ Kinetic gas equation : PV = 1/3 * Mu2

#### Chemical Thermodynamics

↦ ΔU = qv, ΔH = qp

↦ ΔH = ΔU + ΔngRT

↦ C = q/ΔT (C is heat capacity)

↦ ΔU = q + w (First law)

↦ ΔH = ΣΔfH0(Products) - ΣΔfH0(reactants)

↦ ΔG = ΔH - TΔS

↦ ΔG = -RT lnK

↦ CP - CV = nRT

↦ Kinetic gas equation : PV = 1/3 * Mu2

#### Equilibrium

↦ Keq = Kr/ Kb

↦ KP = KC(RT)Δn

↦ Kw = [H+] [OH-]

↦ pH = -log[H+]

↦ pKw = pH + pOH

↦ Ka = Cα2

↦ Kw = Ka * Kb

↦ Ksp = [Ar+]x[B-x]y

#### Solid State

↦ Density = (Z * M)/(a3 * N0) g/cm3

↦ Packing fraction :
Simple cubic = π/6
FCC =√(2π)/6
BCC =√(3π)/8

↦ Bragg's equation : d = nλsinΘ

#### Solution

↦ Henry's law X(g) = KH.P

↦ Raoult's law : v.p. of solution = xAPA0 + xBPB0

↦ Relative lowering of V.P. :(PA0 - PS)/PA0 = Xsolute

↦ ΔTb = ikbm

↦ ΔTf = ikfm

↦ π = CRT

↦ i = no. of particle of solute in solution/no. of particles of pure solute

#### Electrochemistry

↦ Ecell0 = Ecathode0 - Eanode0

↦ ΔGo = -nFEcell0

↦ Ecell0 = Ecell0 - 0.059/n logQ

↦ ⋀eq = k * 1000/Normality

↦ ⋀m = k * 1000/Molarity

↦ λm0 = n+λ+0 + n_λ_0

↦ W=Zlt

↦ W1/W2 = E1/E2

#### Chemical Kinetics

↦ Rate = K[A]x[B]y

↦ K = 2.303/t log[A0]/[At]

↦ t1/2 = 0.693/k

↦ ⋀ k = Ae-Ea/RT

↦ ⋀ Temperature coefficient = KT+10 / KT

#### Naming Compounds

Determining the character of the bond
• Look up the electro-negativity values of the atoms in the bond; subtract the smaller value from the larger value and find the difference in electro-negativity values.
• Compare the difference in electro-negativity to the following:
1. If the electro-negativity difference is ≤ 0.4, the bond is non-polar covalent.In a non-polar covalent bond the sharing non-polar of electrons is even.
2. If the electro-negativity difference is > 0.4 and ≤1.9, the bond is polar covalent;
the sharing of the electron(s) is not even; the atom with the higher electro-negativity takes a greater share of the electron(s) than the atom with the lower electro-negativity. The more electronegative atom develops a partial negative charge and the less electronegative atom develops a partial positive charge.
3. If the electro-negativity difference is greater than 1.9, the bond is ionic. The atom with the higher electro-negativity value takes full control of the electron(s) and becomes a negative ion; the atom with the lower electro-negativity value loses the electron and becomes a positive ion.

Naming Compounds
• Binary Ionic Compounds are compounds containing two monatomic ions; to name them: The name of the positive ion (cation) is written first and then the name of the negative ion (anion) is written with the 'normal' name ending dropped and -ide added.
1. If the positive ion can form ions with more than one charge (multiple valences or oxidation states), a Roman numeral representing the amount of positive charge is written following the name the name of the ion to show the charge.
2. In older systems of naming, the suffix -ic is used to represent the higher valence (oxidation state) and the suffix -ous to represent the lower valence (oxidation state) of the ion.
3. Ionic Compounds containing polyatomic ions: The cation (positive ion) is written and named first, the anion (negative ion) is written and named second. If the anion is the polyatomic ion (most common case) it receives the entire name (do not drop the ending and add an -ide).
4. Naming Binary Molecular Compounds : The less electronegative element is written first (in both the name and the formula); in the name, this atom receives the full name; the second element drops the ending of the elemental name and adds an -ide to the name.
There are two systems for naming molecular substances:
(1) In the older system of naming, prefixes (below), such as mono, di, tri, etc. are used to show the number of atoms (the subscript) of each element in the molecule.
(a). Two rules apply: The first element is prefixed only if there is more than one atom of the element in the molecule;
(b). the second element is always prefixed, no matter how many atoms are in the molecule.
(c). Prefixes indicating numbers of atoms:
 1 atom:mono- 2 atoms:di- 3 atoms:tri- 4 atoms:tetra- 5 atoms:penta- 6 atoms:hexa- 7 atoms:hepta- 8 atoms:octa- 9 atoms:nona- 10 atoms:deca-

(2) In the newer system, the Stock System, prefixes are not used. Instead, the covalence and subscript of the more electronegative (second) element is used to calculate the number of electrons an atom of the first element must share to satisfy it. The name of the first element is written followed by a Roman numeral indicating the number of electrons an atom of that element shares.