Chemistry- difficult topics Flashcards
HDPEs vs. LDPEs & thermosoftening/thermosetting
High density polymers: the polymer chains are interconnecting by polymer chains and form a hard crystalline structure? they are not malleable
Low density polymers:the polymer strands are not joined together by chains and are softer.
Thermosoftening: The polymers can be heated many times and moulded into different shapes.
Thermosetting: the polymers are heated to very high temperatures and are set in a specific shape. When heated again, they cannot change shape
Natural polymers: polysaccarides, polypeptides and dna
Uses of exothermic and endothermic rxs (hand warmers, self-heating cans, ice pack, sherbet)
Reactions with alcohol (with sodium, oxidation, combustion, how it is made (hydration/fermentation)
rechargeable and non rechargeable fuel cells
le Chatelier’s principle
Aristosle, antoine lavosier, Dobreiner, Newlands, Mendeleev
aristostle: four elements, earth, fire, air, water
antoine lavosier: non-metals, metals,earths
dobreiner; grouped elements in threes, the mean of the atomic mass number of the first and third element would equal the atomic mass number of the middle element (grouped elements by chemical properties)
Transition metals and noble gases properties
Required practical, exothermic and endothermic rxs.
Avogadro’s constant
6.02 x 10 ^23
The empirical formula
nano particles, coarse particles, fine particles, buckminser fullerene
Reactivity series of metals
PSLCMAZINTLCSGP
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copper and below dos not reac with acid and steam
Lead and under tarnishes except gold. (Above burns)
PSL explode with acid
PSLCM fizzes in water
NTL react with warm acid or steam very slowly
Extraction of metals
organic acids
ethanoic acid- weak (salts become metal ethanoate)
sulphuric, nitric, hydrochloric acids ae strong
Bases
Metal oxides (react slower and may need to react with hot water as they aren’t soluble
Metal hydroxides
Metal carbonates
Proton transfer rx
Proton transfer rx. are acid-base rx.
concentration
how much solute is dissolved per dm3
Electrolysis, electrode, electrolyte definitions
Electrolysis, breaking ionic compounds down using electricity
Electrode- inert rod that can conduct electricity. usually graphite bc it has a high melting point and can conduct electricity but they must be replaced frequently because they can burn with ocygen at high temperatures.
Electrolyte- ionic solution that can conduct electricity, can be broken down by electroylsis.
To test if chlorine is produced at the anode, damp litmus paper will turn red in the presence of H20
Extraction of alumnium from aluminium oxide
uses: aeroplanes and car bodies, pans, drink cans, window frames,
molten aluminium oxide, cryolite is added to lower the melting point of Al2O3
electrolysed at 950 degrees , lots of energy, high temp required.
electroylsis of ionic solutions
in electrolysis of ionic solutions, less reactive ion will discharge
hydroxide ions will discharge if there are no halides present:
4OH- –> 2H2O + O2 + 4e-
ionic strucutres electric conductivity
in a molten state, some ionic bonds are broken and the ions are no longer fixed in a 3D lattice so they can move through the strucutre to carry charge. ions are alternatively arranged
NPK fertilisers (macronutrients)
salts: mixture of compounds containing nitrogen, phosphorous, potassium, Ratio of NPK value is useful so farmers can choose fertilisers with required properties.
phosphate comes from phosphate cotaining rock but it can not be used straight on the soil as it is insoluble so it can’t be absorbed by roots:
phosphate rock + nitric acid –> phosphoric acid + calcium nitrate
phosphate rock + sulfuric acid –> single superphosphate (made of calcium sulfate + calcium phosphate)
phosphate rock + phosphoric acid –> triple superphosphate (made of calcium phosphate)
potassium salts e.g. potassium chloride and potassium sulfate are mined and are soluble so they are separated from impurities and used directly.
Haber process forms ammonia which can react with nitric acid, sulfuric acid and phosphoric acid to from ammonium salts in NPK fertilisers.
nitrogen - needed for proteins in leaves and stalks
phosphorous- speeds up the growth of roots and helps fruit to ripen.
potassium- speeds up seed growth and improves resistance to disease