BC and hydrocarbons : organic compounds and their formula Flashcards
what do all the homologous series share ?
the same general formula
what can the general formula be used to generate ?
a molecular formula
what is the general formula of alkanes ?
CnH2n+2
what does n stand for ?
the number of carbon atoms in a molecule
give an example of alkane and what is the formula
butane - C4H10
what is the general formula of alkenes ?
CnH2n
give an example of alkene and what is the formula
propene - C3H6
what is the general formula of alcohols ?
CnH2n+1OH
give an example of alcohol and what is the formula
ethanol - C2H5OH
define general formula
the simplest algebraic formula for a homologous series
define a displayed formula
shows the relative positions of atoms and the bonds between them
what is important for displayed formula ?
to show all the bonds
what is an example of this ?
an alcohol group the -OH should be like this -O-H
define structural formula
provides the minimum detail for the arrangement of atoms in a molecule
what is structural formula for butane ?
CH3CH2CH2CH3
what is carboxylic acid and esters shortened into ?
CA -COOH
E -COOR
define an empirical formula
shows the smallest whole - number ratio of atoms of the element in a compound
what is needed to work out the empirical formula ?
the mass of each element
describe step by step how to work out the empirical formula :
1) change the percentages to masses
2) calculate the number of moles of each element using mass/mr = moles
3) divide by the smallest value
4) change the ratio to whole numbers
5) write the formula
define molecular formula
shows the number and types of atoms in a compound
how can one use a three-step method to generate the molecular formula
1) calculate the relative empirical mass using the empirical formula
2) divide the relative molecular mass by the empirical formula mass
3) multiply each atom in the empirical formula by the number calculated in step 2 and write the molecular formula
a hydrocarbon contains 80 % carbon
the compound has a relative molecular mass of 30
a) calculate the empirical formula
b) calculate the molecular formula
c) draw the possible displayed formula
d) state the homologous series it belongs to and it’s general formula
work out yourself :)
a compound contains C=12.79 %
H= 2.15%
Br=85.06%
relative molecular mass = 187.9
a) calculate the empirical formula
b) molecular formula
c) displayed formula
work out yourself :)
what is the general formula for alkanes ?
CnH2n+2
