Before you start

Chemists find out what reactions do in a flask; chemical engineers make them happen at scale, safely and at a profit: refineries, fertilizer plants, drug factories, breweries, water treatment. This course is where the engineering starts. Its one big idea is that nothing appears from nowhere, so you can account for every kilogram and every kilojoule.

From chemistry you need moles and molar mass: a mole is 6.022 × 10²³ molecules, and molar mass is grams per mole (water 18, CO₂ 44, methane CH₄ 16, using H = 1, C = 12, N = 14, O = 16). Moles = mass ÷ molar mass, and kilomoles (kmol) and kilograms work the same way: 18 kg of water is 1 kmol.

A balanced equation gives mole ratios: CH₄ + 2O₂ → CO₂ + 2H₂O says 1 mol of methane needs 2 mol of oxygen. Mass is conserved in a reaction, but moles needn't be: here 3 mol become 3 mol, but in N₂ + 3H₂ → 2NH₃, 4 mol become 2.

Heat: warming something takes mass × specific heat × temperature rise (water's specific heat is 4.18 kJ per kg per °C). Boiling water at 1 atm takes a further 2257 kJ/kg. An exothermic reaction gives out heat; an endothermic one takes it in. The Physical chemistry course covers all of this in depth.

A fraction or percentage tells you what share of a stream is one substance. Mass fraction is that substance's mass ÷ the total mass; mole fraction is its moles ÷ total moles. They're different numbers for the same stream, so always say which you mean.