[{"data":1,"prerenderedAt":110},["ShallowReactive",2],{"cheatsheet-thermochemistry":3},{"sheet":4},{"sheetSlug":5,"topicSlugs":6,"primaryTopic":7,"title":8,"subtitle":9,"sections":10},"thermochemistry",[5],16,"Thermochemistry","Enthalpy, formation reactions, Hess's law, calorimetry, and bond energies.",[11,23,31,39,47,56,64,77,85,93,101],{"heading":12,"kind":13,"items":14},"Endothermic vs exothermic","rules",[15],{"ref":16,"mode":19,"provenance":20,"text":21,"source_hash":22},{"type":17,"topic":7,"id":18,"field":17},"rule","TC-R005","transform","owned_workbook","ΔH > 0 = endothermic (system absorbs heat). ΔH \u003C 0 = exothermic (releases heat). Combustion is always exothermic; report ΔH negative, but report a magnitude when asked 'how much heat is released'.","938ab16d267c40b85d25d3585e3fd140e83f1415201b8e8881a1cd9870b99af4",{"heading":24,"kind":13,"items":25},"Formation reactions",[26],{"ref":27,"mode":19,"provenance":20,"text":29,"source_hash":30},{"type":17,"topic":7,"id":28,"field":17},"TC-R001","Makes exactly 1 mol of compound from elements in their standard states (O₂ g, Br₂ l, C graphite, S rhombic, metals as solids). Fractional coefficients on the reactant side are allowed.","0867f5410f76c90d17ee65fb99ed02563b9e494ff5867df7528735099c709455",{"heading":32,"kind":13,"items":33},"ΔH°f of an element",[34],{"ref":35,"mode":19,"provenance":20,"text":37,"source_hash":38},{"type":17,"topic":7,"id":36,"field":17},"TC-R002","ΔH°f of any element in its standard reference state = 0 kJ/mol by definition (the zero of the formation-enthalpy scale).","1acf2ea228a000f3544a8d10d28b7404cdc2154e82acf4cce0b854a9b84f667d",{"heading":40,"kind":13,"items":41},"ΔH°rxn from formation enthalpies",[42],{"ref":43,"mode":19,"provenance":20,"text":45,"source_hash":46},{"type":17,"topic":7,"id":44,"field":17},"TC-R003","ΔH°rxn = Σ n·ΔH°f(products) − Σ n·ΔH°f(reactants), with n the balanced coefficients. Result is in kJ for the reaction as written; divide by a coefficient for a per-mole basis.","a1a70ac8136b9b24ecd29eba60394fcfce277d7b62a77eda8c5416bd27c84dbd",{"heading":48,"kind":49,"items":50},"Heat for a given quantity","steps",[51],{"ref":52,"mode":19,"provenance":20,"text":54,"source_hash":55},{"type":17,"topic":7,"id":53,"field":17},"TC-R004","mass → moles (÷ molar mass) → heat (× ΔH × the mole ratio from the balanced equation). Reverse the chain to find the fuel needed to release a target amount of heat.","c93ba37da71f7d5e5d2cf27791b12f5c04dbf44dee05e77fb5d30e92d0d7082e",{"heading":57,"kind":13,"items":58},"Hess's law",[59],{"ref":60,"mode":19,"provenance":20,"text":62,"source_hash":63},{"type":17,"topic":7,"id":61,"field":17},"TC-R007","ΔH of an overall reaction = sum of ΔH of any steps that add to it. Reverse a step → flip the sign of ΔH; scale a step → scale ΔH. Intermediates must cancel exactly.","ed63587007175b6cd287c20356e35446533f8b85d28c9c3aaaffac04930159ba",{"heading":65,"kind":13,"items":66},"q = m·s·ΔT",[67,72],{"ref":68,"mode":19,"provenance":20,"text":70,"source_hash":71},{"type":17,"topic":7,"id":69,"field":17},"TC-R008","Q = m·s·ΔT, ΔT = T_final − T_initial. A ΔT in K equals a ΔT in °C (offset cancels).","5107f88703134fdd35df23b2d2c6404245cc9157d61ea3d2ac7fde3886370661",{"ref":73,"mode":19,"provenance":20,"text":75,"source_hash":76},{"type":17,"topic":7,"id":74,"field":17},"TC-R009","Water: s = 4.184 J/(g·°C) = 1.000 cal/(g·°C). Use this for 'water' unless told otherwise; use the given value for other substances.","663560220986ac53193dd38281f4c042d6460f0731d263355eac1173ca4a0bef",{"heading":78,"kind":13,"items":79},"Calorimetry",[80],{"ref":81,"mode":19,"provenance":20,"text":83,"source_hash":84},{"type":17,"topic":7,"id":82,"field":17},"TC-R011","Heat is conserved: Q_hot + Q_cold + Q_cal = 0. The calorimeter constant C_cal (J/°C) is the whole-device value; negligible for a coffee cup unless stated, always significant for a bomb.","f9edce0534ed7940668c5430d8e44b87771a8d1476c49bf4fb8aabb56d87c64a",{"heading":86,"kind":13,"items":87},"Thermal equilibrium (mixing)",[88],{"ref":89,"mode":19,"provenance":20,"text":91,"source_hash":92},{"type":17,"topic":7,"id":90,"field":17},"TC-R010","Same substance, no calorimeter: T_eq = (m_hot·T_hot + m_cold·T_cold) / (m_hot + m_cold). Equal masses → the midpoint. Any consistent temperature scale works (no phase change).","0314e8586b273fb3eda96bf3afd8eb646e044e234be1f45d6af431ce663ba44f",{"heading":94,"kind":13,"items":95},"Bomb calorimetry",[96],{"ref":97,"mode":19,"provenance":20,"text":99,"source_hash":100},{"type":17,"topic":7,"id":98,"field":17},"TC-R014","Constant volume: Q = (m_water·s_water + C_cal)·ΔT. Convert mass burned → moles, then |Q| ÷ moles = heat of combustion per mole (negative). C_cal covers bomb + thermometer + stirrer (given).","2e2e61e2460b1b5fec74301000dc4a3210b685da2d62be2fdce6afc728511666",{"heading":102,"kind":13,"items":103},"Bond energies (gas phase)",[104],{"ref":105,"mode":19,"provenance":107,"text":108,"source_hash":109},{"type":17,"topic":7,"id":106,"field":17},"TC-R016","original","ΔH ≈ Σ E(bonds broken) − Σ E(bonds formed), E = average bond enthalpy (always positive; breaking is endothermic). Estimate only, gas-phase species only.","c570cb70713668770f39db349c4fcf276c615c41379e20d248922b82008ce823",1787246033362]