2.1 - Formulae and amounts of a substance

Define empirical formula

formula showing simplest whole number ratio of atoms in a compound

Define molecular formula

formula showing the actual number of atoms of each element in a molecule

State avogadro’s law

equal volumes of all gases at the same room temperature and pressure contain the same number of molecules

Define molar gas volume

volume of one mole of gas under specified conditions of temperature and pressure

Percentage yield calculation

(actual yield / theoretical yield) x 100

Atom economy calculation

(mass of desired products / total mass of products) x 100

What formula is CH2

empirical

What is needed to find molecular formula?

empirical formula can be calculated and RMM known

Why do we measure gases in volume not mass?

practically easier

Why do we use percentage yield calculations?

amount of product made experimentally often less that why is made based on amount of reactant used

Why is actual yield often different than expected yield?

loss of product on apparatus, reversible reactions, side reactions

Why do we use atom economy - chemical reason?

% yield doesn’t tell extent unwanted products formed in chosen synthesis

Why do we use atom economy - environmental reason?

quantify level of compliance with green chemistry ideal

When do we take % yield into account?

only when asked to do so in question