amount of substances (phys I) Flashcards
simple molecular elements written as a formula
*most have a 2 written after the symbol eg. H2, K2, Cl2
*phosphorus = P4, sulfur = S8
metal + acid —>
salt + hydrogen
metal oxide/hydroxide + acid —>
salt + water
metal carbonate/hydrogencarbonate + acid —>
salt + water + carbon dioxide
ammonia + acid —>
ammonium salt
metal + water —>
metal hydroxide + hydrogen
thermal decomposition of a metal carbonate —>
metal oxide + carbon dioxide
1 ton =
1,000,000g
1 ton =
1,000,000g
carbonate
CO3
hydride
h
formula for hydrochloric acid
HCl
formula for sulfuric acid
H2SO4
formula for nitric acid
HNO3
formula for phosphoric acid
H3PO4
empirical formula
•mass (My)
•big no. (Butt)
•divide (Didn’t)
•smallest (Size)
•divide (Down)
moles =
mass/Mr
no. of particles =
no. of moles x (6.023 x 10^23)
calculating max. theoretical mass
1) calculate no. of moles of substance with known mass (mass/Mr) —> dont incl. big numbers
2) use stoichiometric numbers to get molar ratio & multiply by no. of moles (s. no. of desired substance on top of fraction)
3) multiply no. of moles by Mr of desired substance
% A.E =
- (mass of desired product/mass of total products) x 100
- include stoichiometric no.s
% yield =
(mass of product obtained/max. theoretical mass of product) x 100
reasons for yield being lost
- reaction is reversible
- some reactants may react in side reactions
- reaction may not have gone to completion —> heat to constant mass!
density =
mass / volume
Ideal Gas Equation
pV = nRT
*p in Pa
*V in m^3
*R is 8.31 J/mol/K
*T in Kelvins
converting to Kelvin
temp in celsius + 273
converting to Pa
•mPa x 1000 = kPa
•kPa x 1000 = Pa
Martin —> martin multiplies
Kicked
Pam
converting to m^3
cm^3 /1000 = dm^3
dm^3 /1000 = m^3
Cool
Dinosaurs —> dinosaurs divide
Mew
concentration =
(mol/dm^3)
moles / volume (dm^3)
concentration =
(g/dm^3)
conc. (mol/dm^3) / Mr
>mol/dm^3 also means molarity
>mass = moles/Mr
MGV (molar gas volume) equation
no. of moles = given volume (dm^3) / mgv
molar volumes of gas (expl.)
-if temp & pressure are at standard values, molar volumes of gas can be determined
*standard temp = 273k
*standard pressure = 101300Pa (101.3kpa)
mgv at standard & room temp
*standard temp mgv —> 22.4 dm^3
*room temp mgv —> 24dm ^3
method —> volumetric solution
1) weigh sample bottle containing the solid (on 2dp balance)
2) transfer solid to beaker & reweigh sample bottle
3) record difference in mass
4) add distilled water & stir with glass rod until all solid dissolved
5) transfer to a volumetric flask with washings
6) make upto the 250cm^3 mark w distilled water
7) shake flask
errors —> volumetric solution
*if using anhydrous NaHSo4, ensure it isn’t too old —> it’ll have picked up water —> mass values incorrect
*systematic error of balance —> gives it to 0.01g —> use more acc. balance or calculate diff in mass
*hard to see meniscus behind dark liquid —> place white paper behind
method —> titration
1) pour approx. 100cm^3 known conc. sol. into beaker
2) fill burette with this sol.
3) pour approx 100cm^3 unknown conc. sol. into 2nd beaker
4) use pipette & pipette filler to transfer 25cm^3 of unknown conc. sol. into conical flask
5) add phenolphthalein indicator to conical flask
6) record initial burette reading
7) add sol. in burette to c. flask until permanent colour change —> record final burette reading & calculate change in volume in burette (titre vol.)
8) repeat for 2 concordant results
…protic acids
-monoprotic acid = 1H —> molar ratio is 1:1
-diprotic acid = 2H —> molar ratio is 1:2
-triprotic acid = 3H —> molar ratio is 1:3
calculating concentration from a titration
1) use vol. & conc. of 1 reactant to calculate moles (M=CxV)
2) molar ratio x moles
3) calculate needed conc. of reactant
vol. unit needed for conc. of titration
dm^3
