paper 2 Flashcards
what material is used for the electrodes in electrolysis and why
graphite - it can conduct electricity and it is inert
it needs to be inert so that they don’t participate in a side reaction with the electrolyte
what is the name for the positive electrode
anode (BECAUSE IT ATTRACTS THE ANIONS)
what is the name for the negative electrode
cathode (because it attracts the cations)
what is a binary ionic compound
a compound consisting of just two elements
how do you make an ionic compound molten
- by heating them beyond their melting point
what can you observe during the electrolysis of lead (II) bromide
- bubbling at the anode as brown bromine gas is given off
- grey lead metal at the cathode
what collects at the cathode in the electrolysis of aqueous solutions
- H+ ions and positive ions
what collects at the anode in the electrolysis of aqueous solutions
- OH- ions and negative ions
how can the electrolysis equipment be modified for the collection of gases
by using inverted test tubes over the electrodes
how to predict the products of electrolysis in an aqueous solution
- cathode: the LESS reactive ion becomes an element (between the ion and H+)
- anode: always chlorine, bromine, or iodine if present, otherwise the OH- ions will form H2O and oxygen
what is the half equation for when OH- ions react in electrolysis
4OH- -> O2 + 2H2O + 4e-
what happens to the ions that did not react during electrolysis
they remain as a third product in the solution
what can you observe during the electrolysis of aqueous sodium chloride
- bubbles of pale green chlorine gas
- bubbles of colourless hydrogen gas
what can you observe during the electrolysis of aqueous copper sulfate
- bubbles of colourless oxygen gas
- a pink-orange solid of copper
what can you observe during the electrolysis of dilute sulfuric acid
- bubbles of colourless oxygen gas (as sulfate is not a halide ion)
- colourless gas hydrogen
describe an experiment to set up electrolysis for molten compounds
- add to a crucible and heat
- add two graphite rods and connect this to a battery pack
describe an experiment to set up electrolysis for aqueous solutions
- add solution and electrodes
- invert two small test tubes to collect gaseous products
- connect to a battery pack and turn on
uses of aluminium
- aeroplane bodies - high strength to weight ratio (low density)
- saucepans - goods conductor of heat
- overhead power cables - good conductor of electricity
uses of copper
- electrical wires - malleable and good conductor of electricity
- water pipes - unreactive and malleable
use of low carbon (mild) steel
car body panels and wires - soft and malleable
use of high carbon steel
tools and chisels - hard
uses of stainless steel
cutlery, sinks and chemical plants - strong and resistant to corrosion
what are the makeups of the three different types of steel
iron alloyed with:
- low-carbon (mild) - 0.25%carbon
- high-carbon - 0.5-1.4% carbon
- stainless - 20% chromium and 10% nickel
what is an alloy
a mixture of a metal and one or more elements
what are the three ways that ethanol can be oxidised
- complete combustion
- reaction with oxygen in air (aerobic oxidation)
- heating with dilute potassium dichromate in dilute sulfuric acid
what observations can you see during the complete combustion of ethanol
- burns readily with an almost invisible blue flame
what is the equation for the microbial oxidation of ethanol
ethanol + oxygen -> ethanoic acid + water
observations when treating ethanol with an oxidising agent during the oxidation of ethanol
- potassium dichromate turns from orange to green
- very slow reaction so mixture is heated to its boiling point for an hour and a condenser is placed above to prevent the liquids from escaping
describe the reactions of aqueous solutions of carboxylic acids with metals and metal carbonates
they act exactly the same as acids
the salts formed by the reaction all end in - anoate
eg. magnesium + ethanoic acid -> magnesium ethanoate + hydrogen
what is vinegar
an aqueous solution containing ethanoic acid
what is the key difference between addition polymers and condensation polymers
- addition polymers form the polymer molecule only
- condensation polymers form the polymer molecule and one water molecule per linkage
what is a diol
an alcohol with a functional group at either end
during condensation polymerisation what substance loses what
- dicarboxylic acid loses -OH
- diol loses -H
