Module 2 Flashcards
Relative isotopic mass
Mass of an isotope relative to 1/12 mass of an atom of carbon 12
Relative atomic mass
Weighted mean mass of an atom relative to 1/12 of an atom of carbon-12
Relative molecular mass
simple molecules
Relative formula mass
Giant ionic compounds
Isotopes
Atom of same element with different number of neutrons and different mass.
Isoelectronic
Different physical properties
Avogadros constant
6.02 x 10 ^23 mol-1
Isoelectronic
Same electron structure
Molar mass
Mass in g of one mole of a substance
mass=
Mr moles
Number of particles =
moles x avagadros constant
Empirical formula
Simplest whole number ration of atoms of each element present in a compound
Water of crystallisation
Water that is chemically bonded into a crystalline structure
Calculating the formula of a hydrated salt
1) moles of anhydrous and H2O
2) calculate ratio of amounts and formulas
Check water of crystallisation has been removed by …..
Heating to a constant mass
Concentration
The amount (in mol) of a dissolved substance in 1 dm3 of solution
Moles =
Concentration x volume
Molar gas volume increases as
Temperature increases
Molar gas volume decreases as
Pressure increases
Ideal gas equation
pV= nRT
T in Kelvin (+273)
V (m3)
R = 8.314 Jmol-1K-1
Calculating moles of a gas (RTP)
n = vol/24 (dm3)
Ideal gas equation Conversions
kPa-> Pa X1000
cm3-> m3 X10^-6
Stoichiometry
Ratio of moles in a chemical reaction
Why is a high atom economy good?
-efficient
-produce little waste
-less raw materials used
-sustainable
Atom economy=
(Sum of Mr of desired products/ sum of molar mass of all products) x100
Percentage yield=
(Actual/ theoretical) x100
acids
Release H+ ions when dissolved in water
Proton donor
Strong acids
Fully dissociate when dissolved in water
Weak acids
Partially dissociate when dissolved in water
Bases
Accept H+ ions
Proton acceptors
Examples of bases
-metal oxides
-metal hydroxides
-metal carbonates
-alkalis
alkalis
Dissolve in water releasing OH- ions
Neutralisation
Reaction between acid and base to produce a salt
Neutralisation by carbonate
Acid + carbonate -> salt + water + carbon dioxide
Neutralisation by metal oxide
Acid + metal oxide -> salt + water
Neutralisation by alkali
Acid + alkali -> salt + water
Acid + ammonia
Ammonium salt
Standard solution
Solution of known concentration
Preparing standard solution of NaOH
-mass (e.g. 1.00 g) weighed out and added to beaker
-dissolve NaOH with distilled water use stirring rod
-pour into 250 cm3 volumetric flask
-rinse beaker with distilled water, wash rinsings into flask
-add distilled water until bottom of meniscus on graduation line
-stopper, invert, thoroughly mix
How to find mass needed to prepare standard solution
Find moles (n = cv)
Find mass (m = Mn)
Oxidation number ions
Monatomic- oxidation no= charge
Carrying out acid-base titration
(Finding conc H2SO4 reacting with 25cm3 NaOH)
-Pipette, add 25.0 cm3 NaOH into conical flask
-white tile, few drops of indicator (phenolphthalein or methyl orange)
-burette, sulfuric acid, initial reading, nearest 0.05 cm3
- add sulfuric acid, swirl
-colour change, final reading
- final- Initial = trial titre
-repeat, dropwise near end point until concordant results (within 0.1)
-mean using concordant results
-calculations
Ethanoic acid
CH3COOH
Oxidation number elements
0
Titration finding concentration
Balance equation
Mol known
Mol unknown
Conc unknown
Oxidation no Compounds
Halides -1
H +1
O -2