Topic 1: Stoichiometric Relationships

A sample substance composed of a single type of atom

Atoms of the same element, having the same no. of protons, but with differing no. of neutrons

A mixture of elements in which atoms of various elements chemically combine together in a fixed ratio

The pressure that a liquid’s gaseous form exerts in a closed environment

A liquid in an enclosed chamber will form a dynamic equilibrium with its own vapor: • fast-moving particles in the liquid escape and become vapor • slow-moving particles in the vapor becomes part of the liquid

• as temp. increases, average speed of particles increases - so as temp. increases, equilibrium vapour pressure also increases

A measure of the energy change when 1 mol of liquid converts to gas at standard pressure

The boiling point of a liquid is the temperature at which vapour pressure = atmospheric pressure Elaboration: food in a pressure cooker is cooked faster because of the alteration in boiling point (70 degrees Celsius instead of 100)

The amount of substance containing the same number of atoms as in exactly 12g of the isotope C-12

The average mass of an atom of the element, taking into account all the isotopes and their relative abundance, as compared to 1 atom of C-12

The sum of the relative molecular mass of all the atoms in a molecule

The sum of the relative formula mass of all the atoms in one unit of an ionic compound

Molecule: refers to covalent compounds Formula: refers to ionic compounds

Gives the real number of atoms of the elements present in one molecule of the compound

The simplest whole number ratio of the atoms of elements in one molecule

an equal vol. of gases, both measured at the same temp. and pressure, contain an equal no. of particles. v1/n1 = v2/n2 v: volume n: no. of particles/moles

• no attractive forces between gaseous particles • KE of particles are directly proportional to temp • follows the kinetic particle theory 100%

when the temp is high and pressure is low

the lower the temp. is, the slower molecules move —> the stronger the intermolecular forces

the higher the pressure, the closer molecules are to each other —> the stronger the intermolecular attractive bonds

PV = nRT P: pressure V: volume n: no. of moles R: ideal gas constant T: temp.

at constant temp , pressure is inversely proportional to volume P1V1 = P2V2

P1V1 / T1 = P2V2 / T2 OR PV/T = a constant

C/V = a constant OR c1v1 = c2v2 c = conc V = vol