reacting masses and chemical equations
rules of naming metal and non-metal compounds
-name of metal first -non-metal ending in -ide
rules of naming non-metal/non-metal compounds -
-hydrogen always comes first -element in lower group first
finding formulae of a molecular compound
the type and amount of each atom
findinf formulae of ionic compounds
type and ratio of ions in the compound
what is valency
the valency of an element is how many electons it needs to gain or lose to have a full outer shell
finding formulae with valency
-find valency of every element in compound -write symbols in same order as elements names -if symbols have the same valency write it after the symbols -find formula by balancing charges
how to write equations for reactions
-write word equation -write word equation with symbols -check equation is balannced -add state symbols
laws of chemistry
elements will always react in the same ratio to form a compound -the total mass does not change during a chemical reaction
steps to calculating compostition of compounds
-write down compound formula -write Ar find out Mr -write mass of element as a fraction of Mr -multiply by 100 to get percentage
calculating purity
(mass of pure substance / mass of total substance) time 100