2 Amount of substance Flashcards
define relative atomic mass (Ar)
average mass of an atom of an element on a scale where an atom of carbon-12 is 12
define relative molecular mass (Mr)
verage mass of a molecule on a scale where an atom of carbon -12 is 12.M
define and state the value of the avogadro consatnt
number of atoms in 12g of carbon-12
define the mole
the amount of substance that contains 6.022 x 10^23 aprticles
what is the formula to calculate the number of particles/atoms
number of particles =number of moles x avagadros constant
what is the formula to calculate the number of moles using the Mr
moles=mass/Mr
define the concentration of a solution
how many moles are dissolved per dm^3 of solution the units are mol dm^-3
what is the formula to calculate the number of moles using the concentraion
moles =concentration x volume(dm^3)
what is the formula of the ideal gas equation with SI units
pv=nrt p=pressure (pa) v=volume(m^3) n=number of mole r=8.31 jk^-1 mol^-1 t=temperature(k)
how do you go from degrees to kelvin
add 273
how do you go from cm^3 to dm^3 to m^3
cm^3 —-> dm^3=x10^-3
dm^3 —-> m^3 = x10^-3
cm^3 —-> m^3 = x10^-6
how do you go from kPa to Pa
x 1000
define empirical formula
Empirical formula is the simplest whole number ratio of
atoms of each element in a compound.
define molecular formula
Molecular formula is the actual number of atoms of each element in a compound.
what are the rules for ionic equtions
involves ions that happens in solution only the reacting particles and the products they form are included the overall charges are balanced
what is a spectator ions
ion thats present in the reaction mixture but doesnt get involved in the reaction
write an ionic equation from this balanced equation HNO3 + NaOH —> NaNO3 + H2O
1.HNO3 + NaOH —> NaNO3 + H2O
- ionic substances break up into ions
H+ + NO3- + Na+ + OH- —>Na+ + NO3- + H20
3.cancel out ions on both sides
H+ + OH- —> H20
What is the theoretical yield
mass of product that should be formed in a chemical reaction
it assumes no chemicals are lost in the process
what is actual yield
mass of product that actually is obtained in a recation
why is the percentage yield never 100%
not all reactants had reacted fully
content is lost during transfers between containers
some solution gets left on filter paper
what is the formula to work out percentage yield
percentage yield= Actual yield/theorteical yield X 100
what does the percentage yield tell us
tells us how wasteful a process is as it is based on how much of the product is lost during the process
what is atom economy
tells us in theory how many atoms must be wasted in a reaction
what is the formula to work out atom economy
%atom economy= molecular mass of desired product/sum of molecular masses of all reactants x 100
what are Economic, ethical and environmental advantages for society and for industry of developing chemical processes with a high atom economy.
economic: less expensive as the company will spend less on seperating the desired product from the waste product and also less on treating waste
ethical: chemical companies can find easier, cheaper ways to mass produce medicines and other useful chemicals, this means that the chemicals can be sold for lower prices and therefore be made available to more people
environmental: produce less waste
explain and describe the mothod of tittartion
fill burette with acid
measure amounts of alkali using pippete
add the alkali to a clonical flask with a few drops of suitbale indicator
add the acid from the burette drop by drop until the colour changes
repeat process until you get at least two concordant results
what are the colour changed in the tiration using phenolphthalein and methyl orange
phenolphthalein-colourless in acid and pink in alkali
methyl orange - red in acid to yellow in alkali
