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Flashcards in things to remember Deck (11):


mass of compound/ mass of empirical formula



n = m (mass)/M (Molar Mass)


moles (from atoms)

n = N (particles)/ Na (Avogadro)`


To find mass of excess reactant unreacted

calculate moles reacted then subtract total amount by the amount reacted. times this by M


molecular vs. empirical

molecular: how many atoms of each element in a compound
empirical: the simplest and most reduced RATIO of atoms in a compound


steps for hydrate given a percentage of one Element

1) do the ratio (percent given/mass of element times ()percent x/ ()mass of element.). repeat for number of elements in compound
2) add up percentages, 100-x = percent hydrate
3) assume 100g, find moles, divide by smallest= EF


percentage yield (What is it, find moles unreacted)

is also a ratio
write down everything. to find amount unreacted, find reacted amount (()mol times mol/()mol of other reactant ) then subtract total amount - reacted to get mol unreacted. times by M to get moles excess unreacted


why do you divide by lowest number of moles in EF?

divide because you want to find out how many particles are bonded to each particle of the lowest # of moles


what does chemical formula give you

relative amounts of particles/moles. balanced eqn is needed because it shows the amount of moles in relation to different products


how to go from atoms to mass and back

Order: # of atoms- # of molecular - Moles - mass
EQN: (chemical formula, avogadro, Molar mass)


!!! Molar mass of a compound

is not the molar mass of the EF! It is molar mass of the MF!