Chem Flashcards
Reactivity down Gps 1 and 2
Increases
Reactivity down Gps 6 and 7
Decreases
Colour when Li is burnt
Crimson red
Colour when Na is burnt
Yellow -orange
Colour when K is ignited
Self ignited to burn w/ a lilac flame
Buckminster fullerene
C 60
Ionic eqn for acid + alkali
H+ + OH- —> H2O
Exothermic
Ionic eqn for acid and carbonate
2H+ + CO3^2- —-> H2O + CO2
Ionic eqn acid and ammonia
H+ + NH3 —> NH4+
Physical properties of alkali metals
Low mp and bp - decrease down group (weaker metallic bonding)
Low densities - increase down gp
Soft and become softer down gp
Good conductors of heat and electricity
Chemical properties of alkali metals
V reactive - stored in oil to prevent reactions
When exposed to air - react w/ O2 and tarnish
Reactivity increases down group
Li, Na, K reactions w/ water
Float, moving and fizzing
Produces H2 (squeaky pop)
K - H2 spontaneously ignites and burns lilac
Soluble hydroxide forms
Properties of halogens
Coloured vapours
Low mp and bp, increase down group
Poor conductors of heat and electricity
Reactivity decreases (displacement)
Halogens at RTP
F - pale yellow gas
Cl - Yellow-green gas
Br - Red/brown volatile liquid w/ orange vapour
I - Grey shiny solid, purple vapour when heated
Properties of noble gases
Colourless gases at RTP
V. low mp and bp - increase down the group
Density increases down group
Metals and acid
Salt and H2
Only reacts if metal is more reactive than H2
SO2 (g) + H2O
H2SO3 (aq)
2NO2 (g) + H2O
HNO3 + HNO2
Separating funnel
Sepeartes two immiscible liquids by density
Simple distillation
Separates substances by bp, usually solvent from a solution, leaving solute
Fractional distillation
Separates miscible liquids from a mixture
Similar setup to simple distillation but has fractionating column w/ glass beads
Evaporation and Crystallisation
Separates solvents from solute using diff in bp and/or volatility but target is solute
Heated gently til crystals begin to form (crystallising point)
Why isn’t it recommended to heat to dryness
Some solids may decompose if heated too strongly
Centrifugation
Separates heterogenous mixtures based on diff in particle mass
Encourages settling by spinning at high speed, heaviest settle first
Supernatant decanted into new tube and spun again
Separating gas-gas mixtures
Centrifugation or cryogenic distillation
Why is dc used in electrolysis
So current passes in one direction only
Cathode
Electrons flow from external circuit and enter via this
-ve electrode
Cations are attracted and reduced (metal if LESS reactive than H2)
Anode
e- leave cell via this
+ve electrode
Anions attracted ad oxidised (non-metal)
If complex ion e.g. SO4 ^2-, NO3^- O2 is formed from OH-
Reactivity series
Potassium Sodium Lithium Calcium Magnesium Aluminium CARBON Zinc Iron HYDRROGEN Copper Silver Gold
Electroplating
-ve electrode: object to be plated
+ve electrode: coating metal
Electrolyte - sol of coating metal e.g. metal sulphate or nitrate
Conc of metal ions in electrolyte remains unchanged
Purifying copper
Impure copper - anode
Pure copper - cathode
Copper (II) sulfate solution - electrolyte
Small molecules in crude oil
Low bp
V volatile
Flow easily
Ignite easily
Large molecules in crude oil
High bp
Not volatile
V. viscous
Doesn’t ignite easily
Biodegradable polymers
Break doen after intended use to produce natural products e.g. CO2, N2, H2O
Usually done by microorganisms or enzymes
Often contain ester or amide linkages
Extracting metals
If less reactive than carbon then carbon can be used (or CO)
If more reactive electrolysis is used, split w/ electricity and metal attracted to cathode
Extracting copper
Phytomining (plants)
Bioleaching (bacteria)
Al
Lightweight
Soft and malleable
Corrosion resistant and non-toxic
Uses in aeroplanes (strong and low density), conductor cables, foil, utensils
Ag
Best thermal ane electrical conductor
Antimicrobial and non-toxic: useful in med
Silver nanoparticles inhibit odour in socks
Ti
Strong as steel but less dense
Important alloying agent
Can withstand extremes of temp - aircraft, spacecraft and missilies
Testing for Cl2 gas
Damp blue litmus turns red and then is bleached
Anion tests
Carbonates - dilute acids
Sulphates - BaCl2 in the presence of dilute HCl
Halides - AgNO3 (aq)
Cation tests (0.1 moldm-3) using NaOH
Al^3+, Ca^2+, Mg^2+ - white pp
Cu^2+ - blue ppt
Fe^2+ - green ppt
Fe^3+ - brown ppt
Flame test
Li - crimson red Na - yellow orange K - lilac Ca - red orange Cu - green
Testing for water w/ anhydrous copper (II) sulphate
White –> blue
CuSO4 (s) + 5 H2O —> CuSO4.5H2O
Testing for O2
Blow out burning split, if oxygen present splint relights
SO2
Poisonous, odourless, acidic gas w/ choking smell
Combine w. water –> H2SO4 (aid rain)
Erodes stonework, increases metal corrosion increases leaching
Oxides of nitrogen
React w. water and oxygen in rain —> HNO3 (acid rain)
Toxic gases and can trigger asthma attacks
