Chemistry Calculators

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Chemistry is the scientific study of matter — its composition, structure, properties, and the transformations it undergoes during chemical reactions. It encompasses organic chemistry (carbon-containing compounds), inorganic chemistry (non-organic compounds and materials), physical chemistry (thermodynamics, kinetics, quantum mechanics), analytical chemistry (identification and quantification of substances), and biochemistry (chemistry of living systems). Core concepts include atomic structure and the periodic table, chemical bonding (ionic, covalent, metallic), stoichiometry, thermodynamics (ΔG = ΔH − TΔS), chemical kinetics (rate laws), and acid-base chemistry (pH, pKa, Henderson-Hasselbalch).

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Core Chemistry Concepts

  • Stoichiometry: mole ratios in chemical reactions; molar mass; limiting reagent
  • Thermodynamics: ΔG = ΔH − TΔS; spontaneous if ΔG < 0; ΔG° = −RT ln(Keq)
  • Kinetics: rate = k[A]^m[B]^n; half-life; activation energy; Arrhenius equation
  • Equilibrium: Keq = [products]/[reactants]; Le Chatelier's principle; reaction quotient Q
  • Acid-base: pH = −log[H⁺]; pKa; Henderson-Hasselbalch; Ka × Kb = Kw
  • Electrochemistry: E°_cell = E°_cathode − E°_anode; Nernst equation; Faraday's laws

The Mole Concept

1 mole = 6.022 × 10²³ particles (Avogadro's number). Molar mass (g/mol) = numerically equal to molecular weight in Da. n = m/M (moles = mass / molar mass). c = n/V (concentration = moles / volume in liters).

Glossary

Stoichiometry
Quantitative relationships between reactants and products in chemical reactions; uses mole ratios from balanced equations; moles = mass/molar mass; identifies limiting reagent.
Gibbs Free Energy (ΔG)
ΔG = ΔH − TΔS; determines spontaneity: ΔG < 0 spontaneous; ΔG° = −RT ln(Keq); ΔG = ΔG° + RT ln(Q); = 0 at equilibrium.
pH
pH = −log₁₀[H⁺]; 0–14 scale; pH 7 neutral; each unit = 10-fold [H⁺] change; buffer range = pKa ± 1; blood pH 7.35–7.45.

Frequently Asked Questions

Chemistry is the scientific study of matter, its properties, composition, structure, and the transformations it undergoes. Major branches: Organic chemistry: carbon-containing compounds; functional groups; synthesis. Inorganic chemistry: non-organic compounds; metals; coordination chemistry; materials. Physical chemistry: thermodynamics, kinetics, quantum mechanics, spectroscopy. Analytical chemistry: identifying and quantifying chemical species; chromatography, spectroscopy, titrations. Biochemistry: chemistry in living organisms; proteins, nucleic acids, lipids, carbohydrates, metabolic pathways. Environmental chemistry: chemical processes in the environment; pollution, climate.

Stoichiometry: the quantitative relationship between reactants and products in a chemical reaction. Steps: Balance the chemical equation. Convert given amounts to moles: n = m/M (n = moles, m = mass, M = molar mass). Use mole ratios from the balanced equation to find moles of the desired substance. Convert back to grams, liters, or other units as needed. Identify limiting reagent: the reactant that runs out first and determines the maximum yield. Percent yield = (actual yield / theoretical yield) × 100%.

Gibbs free energy: ΔG = ΔH − TΔS. ΔH = enthalpy change (heat); T = temperature (K); ΔS = entropy change. ΔG < 0: reaction is spontaneous (exergonic) at constant T and P. ΔG > 0: non-spontaneous (endergonic). ΔG = 0: at equilibrium. Standard free energy: ΔG° = −RT ln(Keq); Keq > 1 → ΔG° < 0 (products favored); Keq < 1 → ΔG° > 0 (reactants favored). Non-standard: ΔG = ΔG° + RT ln(Q); at equilibrium Q = Keq and ΔG = 0.

pH = −log₁₀[H⁺]. Ranges from 0 (very acidic) to 14 (very basic) in aqueous solutions at 25°C; neutral pH = 7.0 (pure water). Each pH unit = 10-fold change in [H⁺]. Strong acids (HCl, H₂SO₄): dissociate completely. Weak acids (acetic acid, carbonic acid): partial dissociation; described by Ka and pKa = −log(Ka). Henderson-Hasselbalch: pH = pKa + log([A⁻]/[HA]); buffer is most effective within ±1 pH unit of pKa. Physiological pH: blood 7.35–7.45 (tightly regulated); intracellular pH ≈ 7.2; lysosomes pH 4.5–5.0.