Chemistry Short Notes

Mole = 6.022 × 10²³ particles (Avogadro's number)

n = m / M → n = moles, m = mass (g), M = molar mass

Empirical formula = simplest whole-number ratio of atoms

Molecular formula = n × empirical formula

PV = nRT where R = 8.314 J mol⁻¹ K⁻¹

At STP: T = 273 K, P = 101.325 kPa, V = 22.4 L mol⁻¹

% yield = (actual / theoretical) × 100

ΔH = H_products − H_reactants

Exothermic: ΔH < 0 (releases heat to surroundings)

Endothermic: ΔH > 0 (absorbs heat from surroundings)

q = mcΔT c(water) = 4.18 J g⁻¹ K⁻¹

Hess's Law: ΔH is path-independent — depends only on initial & final states

Bond enthalpy: energy to break one mole of bonds in gaseous state

ΔH_rxn = Σ(bonds broken) − Σ(bonds formed)

Rate = Δ[product] / Δt or −Δ[reactant] / Δt

Factors: concentration, temperature, surface area, catalyst

Activation energy (Eₐ) = minimum energy needed to start reaction

Oxidation = loss of electrons (OIL)

Reduction = gain of electrons (RIG)

Electrolysis: cathode (−) = reduction, anode (+) = oxidation

Q = It Q = charge (C), I = current (A), t = time (s)

Faraday constant F = 96 485 C mol⁻¹