amount of substances in all papers (3.1.2)
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what is the relative atomic mass (Ar)?
the average mass of one atom compared to one twelfth of the mass of one atom of carbon 12. no units.
what is the relative molecular mass (Mr) ?
the average mass of a molecule compared to one twelfth of the mass of one atom of carbon 12. for covalent compounds no units
what is the avogadros constant?
the number of particles in a mole. (6.022x10^23)
how do you work out the number of moles in pure solids and liquids?
moles= mass/Mr units: grams mol
how do you work out the number of moles in pure solids and liquids?
moles= mass/Mr units: grams mol
how do you work out the mass of 1 mole of pariticles?
avogadros constant X mass of 1 parrticle.
how to work out the number of particles?
number of moles x avogadros constant
how do you convert kPa to Pa?
x1000
how do you convert cm^3 to m^3?
divide by 10^6 or x10^-6
how do you convert dm^3 to m^3?
divide by 10^3 or x10^-3
how do u convert C to kelvins?
add 273
how do you work out the empirical formula and molecular formula from it?
1: set out the elements with their masses/percentage. 2: divide each mass by their Mr. 3: divide all them by the smallest value. 4: give whole number ratio in empirical formula. 5: molecular formula = n(empirical formula)
explain the water of crystallisation practical (hydrated salt)
• weigh an empty crucible. • add 2g of hydrated calcium sulfate to the crucible and weigh again. • heat with a bunsen burner for 5 mins and let it cool. • weigh the crucible and contents again. • heat and reweigh again until you reach a constant mass to ensure salt has become anhydrous.
how do you work out atom economy?
mass of desired product ————————————–x100 total mass of reactants
how do you work out percentage yield?
actual mass of product ————————————–x100 maximum theorectical mass of product
why might a chemical reaction not give a 100% percentage yield?
• reactants react in a different way. • reaction doesnt go to completion, the reaction is reversible. • some reactant or product is lost during reaction or seperation or purification.
define the concentration of a solution?
• the number of moles of solute in 1dm^3 of solution?
how do you calculate the number of moles in a solute in a given volume?
• moles = concentration x volume
list the steps of titration?
• pipette 25cm^3 of the HCL into the conical flask. • add the indicator • fill the buette with the NaOH solution. • make sure the jet space in the burette in the solution and air bubbles are removed. • take the initial burette reading • add the NaOH • stop adding NaOH when the indicator changes colour and record the final burette reading. • work out titre volume.
titration how do you record the volume decimals
• to 2 d.p
titration how do you work out the titre volume?
final burette reading - initial burette reading
titration when do you have concordant results?
• when you have 2 titre volumes within 0.1
titration why is a conical flask used instead of a beaker?
• to prevent loss of solution from splashing.
titration why should we only add a few drops of indicator?
• its slightly acidic, too much will interfer with results.