PHYSICAL - AMOUNT OF SUBSTANCE Flashcards
Relative atomic mass
the average mass of an atom of an element relative to one twelfth of the mass of an atom of carbon-12.
Relative molecular mass
Ratio of the mass of 1 molecule to 1/12 of the mass of carbon-12
Avogadro’s constant
6.02x10^23
Equation linking concentration and volume
amount
amount(mol/g) = conc x vol
cm3/1000 = dm3
conc = mass/volume
Equation linking mass and Mr
mass = mol x Mr
Titration calculation
0.25dm3 of a solution of CuSO4 weighs 47g. Calculate conc in mol dm-3:
Mr of CuSO4 = 159.6
mol = 47/159.6 = 0.294mol
0.294/0.25 = 1.18moldm-3
Back titration
A metal carbonate, M2CO3 reacts with HCl -> M2CO3 + 2HCl –> 2 MCl + CO2 + H2O. 4.5g M2CO3 dissolved to make a 250cm3 solution - 25cm3 of this was neutralised by 28.9cm3 of 0.148moldm-3 HCl.
- Calc mol of HCl in 28.9cm3 of 0.148moldm-3 HCl:
28.9/1000 x 0.148 = 4.28x10-3 mol - Calc mol of M2CO3 that reacted with this HCl
(4.28x10-3)/2 = 2.14x10-3mol - Calc mol of M2CO3 in the 4.5g sample
2.14x10-3 x 10 = 0.0214mol - Calculate RFM of M2CO3
Mr = mass/mol
4.5 / 0.0214 = 150.3
150.3+12+(16x3) = 210.3 Mr
Ideal gas equation
PV = nRT
P = pressure (Pa) KPa -> Pa = x1000
V = vol (m^3) cm3 -> m3 = /1000000
n = mol
R = gas constant
T = Kelvin (K) °C -> K = +273
Empirical formula
Simplest whole number ratio of atoms of each element in a compound
Molecular formula
Actual number of atoms of each element in a compound
EF calculation
- Divide mass/% of element by its Ar
- Work out simplest ratio
- Formula
MF calculation
- Divide actual Mr of compound by Mr of EF
- Multiply EF by answer
Hydrated compounds
- Mass/atomic mass
- Ratio
- Formula
Atom economy
(Mr of useful product/Mr of all products) x100
Efficient processes: High AE, important for sustainable development as less waste produced and less natural resources used
Wasteful products can be sold for profit