chapter 3 Flashcards
what is one mole
one mole of a substance is the amount of substance which contain as many formula units as there are atoms in 12g of carbon 12. 6.02 x 10^23
units of mol
g mol^-1
moles equation
moles = mass/molar mass
what is molecular formula?
number of atoms of each element in a compound
what is emperical formula
simplest whole number ratio of the ratio of atoms of each element in a compound
when is emperical formula used?
when substances arent molecules and instead exist as giant crystaline structure
what is relative molecular mass
mr - compares mass of a molecule w the mass of a carbon 12 atom
how is relative formula mass different to relative molecular madd?
it is the total atomic mass for an emperical formula compound
how to calculate emperical formula from mass?
convert mass into moles, divide the moles by the value w the smallet moles
how to calculate molecular formula from percentages?
percentage/Mr
divide moles of each value by the smallest mole
then do the relative molecular mass/mr of emperical formula
take the value and times it by the emperical formula e.g. ch2o x 6 = c6h12o6
why are coloured crystals said to be hydrated?
water is a part of there structure
anhydrous
when water is removed, turns white
why is getting the formula from an experiment not always accurate?
- assumes all water has been lost (if colour change is little its hard to tell when al water is lost, so keep heating till mass no longer changes)
- assumes there is no further decomposition (salts decompose and change colour when heated, so its hard to judge colour change)
1cm3 in ml
1ml
1 dm3 in cm3
100cm3
1 dm3 in ml
1000 ml
1 dm3 in l
1l
concentration equation
n=c x v
what is a standard solution?
a solution of known concentration
how is standard solution produced?
dissolving an exact mass of solute in a solvent making the solution to an exact volume
how to work out standard solution calc
find mol of substance using n = c x v
use m=n x mr to find mass that needs to be dissolved
what is molar gas volume?
Vm - volume per mole pf gas molecules at a stated temperature and pressure
what is STP
standard temperature and pressure
what is RTP
room temperature pressue, 24 dm3 mol^-1
20 c and 101 kpa
molar gas volume equation
moles = volume/Vm
if dm3 24
if cm3 24000
limitations of RTP
conditions are not always room temperature and pressure
ideal gas equation
pV = nRT
units for ideal gas equation
p - pressure pa
V - volume m3
n - mol
R - gas constant - 8.34jmol-1k-1
T - tem - kelvin
cm3 to m3
dm3 to m3
c to k
kpa to pa
x 10^-6
x10^-3
+273
x 10^3
what is the ratio of balanced equations called?
stoichemotry
percentage yield equation
actual yield/theoretical yield x 100
why is theoretical yield less than actual yield?
reaction not gone to completion
side reactions may have taken place
purification of product may mean loss of some product
what is atom economy used for?
measure of how well atoms have been utilised
atom economy equation
mr of desired product/mr of all products x 100
why is high atom economy important?
produce large proportion of desired product
sustainability make best use of natural resources
