What are the 5 main types of chemical reactions? — 1. Synthesis: A + B → AB. 2. Decomposition: AB → A + B. 3. Single displacement: A + BC → AC + B. 4. Double displacement: AB + CD → AD + CB. 5. Combustion: Fuel + O₂ → CO₂ + H₂O.

What is a synthesis (combination) reaction? — Two or more substances combine to form a single product. Example: 2H₂ + O₂ → 2H₂O. 2Na + Cl₂ → 2NaCl.

What is a decomposition reaction? — A single compound breaks down into two or more simpler substances. Example: 2H₂O₂ → 2H₂O + O₂. Often requires heat, light, or electricity.

What is a single displacement reaction? — A more reactive element displaces a less reactive element from a compound. Example: Zn + CuSO₄ → ZnSO₄ + Cu. Determined by the activity series.

What is a double displacement (metathesis) reaction? — Ions of two compounds exchange partners. Example: AgNO₃ + NaCl → AgCl↓ + NaNO₃. Often forms a precipitate, gas, or water.

What is a combustion reaction? — A substance (usually hydrocarbon) reacts rapidly with oxygen, releasing heat and light. Complete combustion: Fuel + O₂ → CO₂ + H₂O. Incomplete combustion produces CO and soot (C).

What is the law of conservation of mass? — Matter cannot be created or destroyed in a chemical reaction. The total mass of reactants = total mass of products. This is why we balance equations.

How do you balance a chemical equation? — Adjust coefficients (numbers in front of formulas) so the number of each type of atom is equal on both sides. NEVER change subscripts in formulas. Example: H₂ + O₂ → H₂O becomes 2H₂ + O₂ → 2H₂O.

What is molar mass? — The mass in grams of one mole of a substance. Equal to the sum of atomic masses of all atoms in the formula. Example: H₂O = 2(1) + 16 = 18 g/mol.

What is the mole formula triangle? — Moles = Mass (g) ÷ Molar Mass (g/mol). Rearranged: Mass = Moles × Molar Mass. Molar Mass = Mass ÷ Moles.

What is stoichiometry? — The calculation of quantities (moles, mass, volume) of reactants and products in a chemical reaction, based on the balanced equation's molar ratios.

How do you use molar ratios in stoichiometry? — The coefficients in a balanced equation give the mole ratio. Example: N₂ + 3H₂ → 2NH₃. If 1 mol N₂ reacts, it uses 3 mol H₂ and produces 2 mol NH₃.

What is a limiting reagent (reactant)? — The reactant that is completely consumed first and determines the maximum amount of product that can be formed. The other reactant is in excess.

How do you find the limiting reagent? — 1. Convert each reactant to moles. 2. Divide moles by each reactant's coefficient. 3. The smallest result is the limiting reagent. Then use limiting reagent moles to calculate product.

What is theoretical yield? — The maximum amount of product that could be produced if the reaction goes to completion with no losses. Calculated from stoichiometry using the limiting reagent.

What is actual yield? — The amount of product actually obtained from an experiment. Always ≤ theoretical yield due to incomplete reactions, losses during collection, and side reactions.

What is the percent yield formula? — % Yield = (Actual Yield ÷ Theoretical Yield) × 100%. A 100% yield is ideal but rarely achieved. A yield > 70% is generally considered good in organic chemistry.

What is molarity (M) and its formula? — Molarity = concentration of a solution in moles per litre (mol/L). Formula: M = moles of solute ÷ volume of solution (L). Example: 2 mol NaCl in 0.5 L = 4 M NaCl.

What is dilution and its formula? — Adding solvent to decrease a solution's concentration. Formula: M₁V₁ = M₂V₂ (moles before = moles after dilution). Example: Diluting 1 L of 6M HCl to 3 L gives 2 M HCl.

What is the ideal gas law? — PV = nRT. P = pressure (atm), V = volume (L), n = moles, R = 0.0821 L·atm/mol·K, T = temperature (Kelvin). Describes behavior of an ideal gas.

What is STP (Standard Temperature and Pressure)? — Temperature = 273 K (0°C) and Pressure = 1 atm. At STP, one mole of any ideal gas occupies 22.4 L (molar volume).

What is an exothermic reaction? — A reaction that releases energy (heat) to the surroundings. ΔH is negative. The products have lower energy than the reactants. Example: combustion, neutralization reactions.

What is an endothermic reaction? — A reaction that absorbs energy (heat) from the surroundings. ΔH is positive. Products have higher energy than reactants. Example: photosynthesis, dissolving ammonium nitrate in water.

What is a precipitation reaction? — A double displacement reaction that forms an insoluble solid (precipitate) when two aqueous solutions are mixed. Example: Pb(NO₃)₂ + 2KI → PbI₂↓ (yellow precipitate) + 2KNO₃.

What is an oxidation-reduction (redox) reaction? — A reaction involving the transfer of electrons. Oxidation = loss of electrons (OIL). Reduction = gain of electrons (RIG). OIL RIG — the substance oxidized is the reducing agent; reduced = oxidizing agent.