Class 11 Chemistry Formulas Study Guide

Avogadro's Number: The constant representing the number of constituent particles (usually atoms or molecules) in one mole of a substance is defined as: $N_1 = 6.022 \times 10^{23}$
Calculation for Number of Moles ( $n$ ): The number of moles is determined by the ratio of the mass of the substance to its molar mass: $n = \frac{\text{Given mass}}{\text{Molar mass}}$
Total Number of Particles: To find the absolute number of particles in a sample, multiply the number of moles by Avogadro's number: $\text{Particles} = n \times N_1$
Molarity ( $M$ ): A measure of the concentration of a solute in a solution, defined as the number of moles of solute per liter of solution: $M = \frac{\text{moles of solute}}{\text{volume in litres}}$

Mass Number ( $A$ ): The total number of protons and neutrons in an atomic nucleus: $A = Z + N$ * $Z = \text{protons}$ * $N = \text{neutrons}$
Energy of electron (Bohr's model): The energy level of an electron in a specific orbit ( $n$ ) according to the Bohr model is expressed as: $E_n = -13.6\,eV$
Wavelength formula: Based on the de Broglie hypothesis, the wavelength of a particle is related to its momentum: $\lambda = \frac{h}{m \times v}$

Formal Charge ( $FC$ ): This is the charge assigned to an atom in a molecule, assuming that electrons in all chemical bonds are shared equally between atoms, regardless of relative electronegativity: $FC = \text{Valence electrons} - \text{Non-bonding electrons} - \frac{1}{2}(\text{Bonding electrons})$
Dipole Moment ( $\mu$ ): This measures the polarity of a chemical bond within a molecule, calculated as the product of the magnitude of the charge and the distance between the centers of positive and negative charges: $\mu = q \times r$

First Law of Thermodynamics: A version of the law of conservation of energy, adapted for thermodynamic processes, stating that the change in internal energy is equal to the heat added to the system plus the work done on the system: $\Delta U = q + w$
Calculation for Work Done ( $w$ ): In terms of pressure and volume change, work is defined as: $w = -P \times \Delta V$
Enthalpy Change ( $\Delta H$ ): The total heat content of a system, defined as the sum of the internal energy and the product of pressure and volume: $\Delta H = \Delta U + P \times \Delta V$

Oxidation: Defined as the chemical process involving the loss of electrons by a molecule, atom, or ion. * Example half-reaction: $Zn \rightarrow Zn^{2+} + 2e^{-}$
Reduction: Defined as the chemical process involving the gain of electrons by a molecule, atom, or ion. * Example half-reaction: $Cu^{2+} + 2e^{-} \rightarrow Cu$
Cell Notation Example: A symbolic representation of an electrochemical cell showing the anode and cathode divided by phase boundaries and a salt bridge: $Zn \ || \ Zn^{2+} \ || \ Cu^{2+} \ | \ Cu$