module2- Section 2

what is the empirical formula?

the smallest whole number ratio of atoms of each element in a compound

what is the molcular formula?

the actual number of atoms of each element in a molecule. it is made up of a whole number of emperical units.

how can you work out the moleular formula if you know the emprical formula and the molecular mass?

1- find the mass of the emperical formula

2- divide the molecular mass by the empirical mass. this tells you how many multiples of the empirical formula fit into the molecular formula

3- multiply this number by the empirical formula

how do you calculate the empirical formula from experimental data?

* use the equations moles=mass/mr
* use the moles of each product made to work out how many moles of each atom you started with
* write down the ratio of moles present at the start
* divide by the smallest number of moles to get the smallest whole number ratio
* this tells you the empirical formula

mass of reactant A=

mass of product- mass of reactant B

what is included in ionic equations?

only the reacting particles are included. they show the reactions involving ions.

what does the reaction stoichiometry tell you

the ratios of reactants to products. i.e. how many moles of a product are formed from a cetain number of moles of reactants

how are ions formed?

ions are formed when electrons are transfered from one atom to another. the simplest ions are single atoms which have either lost or gained electrons so that they can have a full outer shell.

what is the formula of a nitrate ion?

NO3(-)

what is the fomula of a carbonate ion

CO3(2-)

what is the formula for a sulfate ion

SO4(2-)

what is the formula for a hydroxide ion?

OH-

What is the formula for an ammonium ion?

NH4(+)

how are ionic compounds made?

when positive and negative ions bond together. they do this through ionic bonding. The charges in ionic compounds must always balance out to equal zero.

how do you work out the formula for ionic compounds

work out the ratio beween the positive and negative ions so that the total of all negative charges is the same ass the total of all positive charges