1.2 amount of substance (notes)

gases and volatile liquids follow the ideal gas equation under standard conditions

pV = nRT

p = pressure in Pa

V = volume in m³

m³ ← ÷1000 — dm³ ← ÷1000 — cm³

n = amount in moles

R = ideal gas constant = 8.314 J K^-1 mol^-1

T = temperature in K

°C —1000 → K

percentage yield: a measure of the efficient conversion of reactants to products / idea of getting as much product as possible in the reaction

• (mass of product actually made / maximum theoretical mass of product) x 100

for percentage atom economy calculations, use the coefficients

high percentage atom economy =

• little to no waste product, only the desired product, so more economically viable for industrial scale manufacture

• less mass of reactants that end up as waste, so the reaction is more sustainable.

• less natural resources used so less energy used, so beneficial for the environment

atom economy: maximising mass of reactants that end up as desired product, minimising amount of by-products

• (Mr of desired product / sum of Mr of all reactants) x 100

improving percentage atom economy:

• cannot be improved.

• sell the by-product to increase profits.

if there is only product in a reaction, the atom economy is 100%

transition metals can form different ions so have variable oxidation states thus they can be used as catalysts to lower the activation energy of a chemical reaction.

in the Solvay Process, ammonia is not considered a raw material because:

• ammonia is used up but then regenerated later in the cycle

• no overall consumption of ammonia

• can act as a catalyst

in the Ostwald Process, excess air is used to:

• ensure all the ammonia is used up/ensure a complete reaction or combustion.

• maximise the yield of nitric acid.

when heated, iron(Il) nitrate is converted into iron(lll) oxide, nitrogen dioxide and oxygen:

4Fe(NO₃)₃(s) —> 2Fe₂O₃(s) + 12NO₂(g) + 3O₂(g)

this reaction is thermal decomposition.

the iron(III) oxide is pure because:

• the other products are gases/escape easily.

• there’s no other solid (or liquid) product.

it’s hard to separate 2 solids/liquids/gases produced by a reaction, which makes it difficult to obtain a pure sample

percentage yield of a product may decrease if:

• the product is a gas so easily escapes.

• product may be lost during filtration.

• not all of the reactants react (especially in reversible reactions).

• there are by-products.

• there are side reactions making other products).

• impure reactants are used.