The mole Flashcards
(42 cards)
The mole?
(The unit for) the amount of substance that contains the same no. particles as the no. C atoms in 12g of C-12 isotope
- 1 mol = 6.02x10^23 atoms/molecules aka Avogadro’s Constant (L)
- e.g. 1 mol of H2O contains 6.02x10^23 molecules of H2O
-e.g. 1 mol of Fe contains 6.02x10^23 atoms of Fe in 56g of Fe
- no. O atoms in 16g of O is the same as the no. H atoms in 1g of H
Avogadro’s constant definition?
the number of atoms of C-12 in exactly 12g of C-12
Calculating the no. particles in a substance?
no. particles = Avogadro’s constant (L) x no. moles
- can rearrange*
n, m, Mr
n = m(g)/Mr/Ar
The mole - solutions: n, c, v
n = c (mol dm^-3) x v (dm^3)
Avogadro’s Law?
equal vols of gas under the same conditions of temp & pressure contain same no. molecules
- 1 mole of any gas occupies exactly the same vol
*use ratio
cm^3 –> dm^3
/1000 or x10^-3
Empirical formula definition + working out?
The simples whole number ratio of each element in a compound
1. write out elements involved
2. write percentages as masses
3. / by Ars to get no. moles
4. / all nums by smallest no. moles
- if e.g. looking at only hydrocarbon only look at C + H but still same process
empirical formula, Mr, n
Mr = (Mr of) empirical formula x n
Mr/Mr of empirical = n -> n x atoms
e.g. if 1 mole of CO2 or if 1 mole of H20, how many moles of C & H do you have?
1 mole of C
2 mol of H (x no. mol of molecule by 2)
Ionic equations - how to write?
show ions that r formed in solution (normally acids, bases + salts) & which particles r reacting
1. write ionic equation underneath - split all (not H2O)
2. cancel any ions that remain the same - state & ion
- spectator ions: don’t take part in reaction
Working out theoretical masses? (skip)
- write equation + balance
- Work out Mr/Ar of species involved - write as mass in g (take into account big num)
- divide side ur given by the its mass num to get 1g then x by the given mass (e.g. 80/80 x 34)
- do same on side ur trying to figure out (e.g. 112/80 x 34)
Displacement reaction?
More reactive element takes the place of a less reactive element in a compound
acid + base & acid + carbonate
salt + water…+ CO2
Precipitation reactions?
when an insoluble solid is produced after 2 aqueous reactants react
- e.g. test for CO2, sulfates & halide ions
The mole - gases?
- gases occupy the same vol of space under same conditions
n = v (dm^3) / molar gas volume
Molar (gas) volume?
the volume 1 mol of gas occupies (dm^3mol^-1)
- standard room temp & pressure = 24
- standard temp & pressure = 22.4
Finding the vol of gas experimentally?
- collecting gas in gas syringe
- upturned measuring cylinder filled w water
Calculating the total amount (volume) of gas produced?
- use big nums to work out no. moles of gas produced overall (add)
- x vol given by no. moles
The mole - Ideal gas equation?
the no. moles in a specific vol of gas
pV = nRT
- p = pressure (Pa) kPa -> Pa: x 1000
- V = volume (m^3) m^3 -> cm^3: x 10^6
- n = moles (mol)
- R = gas constant (8.31 JK^-1mol^-1)
- T = temperature (K)
Ideal gas equation - standard conditions?
- 298K
- 100kPa
m^3 dm^3 cm^3
m^3 x 1000 = dm^3
dm^3 x 1000 = cm^3
Using equations to work out vol of gases?
- write out equation & balance
- work out no. moles of what u know
- use eq to find out molar ratio - find moles of unknown
- use ideal gas equation to work out vol
Risks examples
scalding - hot liquids
- burns - hot equipment
- burns - chemicals
- cuts - glass/metals
- harm/poisoning - gases/chemicals
