C6 Flash cards

Anna Hollywood
Flashcards by , created over 5 years ago

GCSE Chemistry (C6) Flashcards on C6 Flash cards, created by Anna Hollywood on 10/26/2013.

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Anna Hollywood
Created by Anna Hollywood over 5 years ago
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Question Answer
What is made at the cathode during copper electrolysis? Cu2+ + 2e- --> Cu
What is made at the anode during copper electrolysis? Cu - 2e- ---> Cu2+
During copper electrolysis... the cathode gets heavier/lighter the anode gets heavier/lighter The cathode gets heavier The anode gets lighter
Why doesn't CuSO4 (aq) change during copper electrolysis? Cu2+ replaced by anode
What is electrolysis? - Splitting something using electricity - It is the flow of charge created by moving ions and the discharge of ions at the electrodes
Can solids do electrolysis and why/why not? No because there are no moving charges
What is formed at the cathode and anode during the electrolysis of sodium hydroxide? Cathode (is negative) - Hydrogen (is positive) Anode (is positive) - Oxygen (is negative)
Metals are discharged at cathode/anode Non-metals are discharged at cathode/anode Metals are discharged at cathode Non-metals are discharged at anode
Why are fuel cells used in spacecraft? - The water produced isn't wasted-the astronauts drink it - They are lightweight (normal batteries are heavier) - They are compact - They have no moving parts
How do fuel cells produce water? The oxygen is used to neutralise the hydrogen and make water
Why is the quality of no moving parts in a fuel cell good? It therefore makes it more efficient at producing an electric current
Why is it important that the fuel cells work at low temperature? So it doesn't need burning and so no oxides of nitrogen are produced
What do fuel cells do? Produce electric current
4 advantages for using fuel cells in cars - They don't produce carbon dioxide - Car manufacturers are looking for alternate fuels that don't use (non-renewable) fossil fuels - The main product of a hydrogen-powered fuel cell is water (not a pollutant) - Hydrogen is widely available
When does a positive ion produce hydrogen and when does it just produce the metal? It produces hydrogen if its in group 1,2,3 and it produces the metal if its in group 4,5,6
When does a negative ion produce hydroxide(to make oxygen) and when does it just produce the non-metal? It produces a non-metal if it's just 1 element, if its more than one element it produces hydroxide(to make oxygen)
Name 5 advantages of using fuel cells - Direct energy transfer - All done in one stage - More efficient due to it only taking one stage - Less polluting - Last longer than conventional rechargeable batteries
What are two half equations for what happens at the anode and cathode when sodium hydroxide solution and sulfuric acid react? At the cathode: 2H+ + 2e- → H2 At the anode: 4OH- - 4e- → O2 + 2H2O
What are the 2 disadvantages of using fuel cells? - They often contain poisonous catalysts which need to be disposed of at the end of its life - Fossil fuels are burnt to produce the oxygen and hydrogen needed
What is the overall equation for a hydrogen oxygen fuel cell? 2H2 + O2 --> 2H2O
The anode equation in a hydrogen oxygen fuel cell is... 4H+ + O2 + 4e- --> 2H2O
The cathode equation in a hydrogen oxygen fuel cell is... 2H2 ---> 4H+ + 4e-
What is the sort of reaction where it involves both reduction and oxidation? A redox reaction
What's an example of a redox reaction? Rusting
How can you protect iron from rusting? Why does this work? You can galvanise it with zinc. the zinc layer stops water and oxygen from reaching the surface of the iron. Zinc acts as a sacrificial metal as its more reactive than iron
What is the oxidising agent when iron rusts? Oxygen
How does oxygen work as an oxidising agent for rusting? It takes electrons from the iron and the electrons go onto the oxygen so the oxygen itself has been reduced
Are positive ions metals or non metals? Metals
Why can't an ionic solid not be electrolysed? Because the ions are in fixed positions and cannot move.
Why is recharging fuel cells counted as electrolysis? Because it involves splitting the water back into hydrogen and oxygen
How do you know if a reaction is a redox reaction? It will have both a metal and non-metal as the reactants
What happens in a displacement reaction? The more reactive metal swaps places with the less reactive metal (in the compound)
How does displacement work? The metals react by pushing off electrons and turning into ions. Theses electrons are forced onto the ions of other metals that are not so reactive. Metal atoms that gain these electrons are reduced
What's the word equation for making ethanol through fermentation? glucose ---> ethanol + carbon dioxide
What's the balanced symbol equation for making ethanol through fermentation? C6H12O6 ---> 2C2H5OH + 2CO2
What does the process of fermentation involve? 1) The reaction is catalysed by the enzymes in yeast 2) This will only happen if there is NO oxygen present 3) The dilute liquid undergoes fractional distillation to purify ethanol - Glucose has to be a solution - It has to be room temp
What is the general formula for alcohols? CnH2n+1OH
Why is making ethanol to use as a fuel renewable? Because the plants that make the sugar for the process grow quickly
why is producing ethanol from ethane non-renewable? Because ethene comes from fossil fuels which are a finite resource
What is the reaction to make ethanol from ethane called? Hydration
What is the word equation for the hydration of ethane? ethene + water ----> ethanol
What conditions are needed for hydration? For then ethene and steam to be passed over a hot phosphoric acid catalyst
What is the balanced symbol equation for the hydration of ethene? C2H4 + H2O ----> C2H5OH
Fermentation/hydration has a high/low atom economy and yield Fermentation- Low Hydration -High
Why were chlorofluorocarbons thought to be a great discovery? Because they were so inert (unreactive)
What discoveries have scientists made about the CFCs? That they are broken down in the stratosphere by UV light to make highly reactive chlorine atoms. Scientists and politicians agreed that they should be banned
What can CFCs be replaced with? Alkanes or hydrofluorocarbons
What are the 3 main steps in chlorine depleting the ozone? 1.CFC molecules reach the stratosphere. Ultraviolet radiation breaks them down, releasing highly reactive chlorine atoms. For example: CCl3F → •CCl2F + •Cl The chlorine atoms are called chlorine radicals. They are shown as •Cl in equations. 2.Chlorine radicals react with ozone molecules, breaking them down 3.The reactions in step 2 regenerate the chlorine radicals, so they can go on to destroy more ozone molecules.
How is the radical formed in CFCs? When a CFC molecule absorbs ultraviolet radiation, a carbon-chlorine bond breaks. One of the shared electrons goes with the released chlorine atom, while the other stays with the remainder of the CFC molecule. These unpaired electrons are shown as dots in formulae for radicals, such as •Cl (a chlorine radical).
What are the equations for how CFCs work? 1.CCl3F → •CCl2F + •Cl 2.•Cl + O3 → •ClO + O2 3.•ClO + O3 → •Cl + 2O3
Do the chlorine radicals ever stop? It takes a while as what they react with is random so it could take a while until it reacts with something that will stop it
how is hard water formed? When rainwater dissolves some of the rock that it flows over
How is it temporary hard water formed? What is the word and symbol equation for this? Made by CaCO3 in rocks reacting with dissolved CO2 and water. calcium carbonate + water + carbon dioxide → calcium hydrogencarbonate CaCO3 + CO2 + H2O ---> Ca(HCO3)2
Can permanent hardness be removed by boiling? No
What is permanent hardness caused by? calcium sulfate
Can temporary hardness be removed by boiling? Yes
How do you remove permanent hard water? Using washing soda - CaSO4 + Na2CO3 ---> CaCO3 + Na2SO4
How do you remove temporary hard water? Ca(HCO3)2 + Na2CO3 ---> CaCO3 + 2NaHCO3
What does heating do to temporary hardness? Removes the soluble calcium ions from the water by changing then into insoluble calcium carbonate
How does ion exchange work to remove water hardness? The water flows over beads of solid resin which trap the calcium ions and swap them for sodium ions.
Why is hard water so bad? Because it wrecks anything with a heating element in it
What types of chemicals are fats & oils? Esters
Do saturated fats have single or double covalent bonds? Single
Why are saturated fats bad for you? Because your body can't break them down as they clog up your arteries and cause heart disease.
What do unsaturated compounds that react with bromine water produce? A colourless dibromo compound
How is margarine made? 1)The sunflower oil reacts with the hydrogen gas using a nickel catalyst (to harden the oils) 2) Its mixed with fat free milk, flavourings and emulsifier 3) The hydrogen reacts with the carbon-carbon double bonds and turns them into single bonds
Is the head of an emulsifier hydrophilic or hydrophobic? Hydrophilic
What's an example of a water in oil emulsion? Butter
What's an example of an oil in water emulsion? Milk
Why are emulsions formed? When immiscible liquids such as oil and water are mixed. They will eventually separate without an emulsifier
What is saponification? its the process of splitting up natural fats and oils using sodium hydroxide solution, to make soap
What is the name of the saponification reaction? A hydrolysis reaction
What are the reactants and reaction conditions for saponification? The reactants are fat/oil and sodium hydroxide. The sodium hydroxide needs to be hot
What is the word equation for saponification? fat + sodium hydroxide --> soap + glycerol
Why is it good to wash at low temperatures? - it saves you money on your energy bills - less damaging to certain fabrics (such as those made from animal proteins which will denature in high temperatures)
What are detergents a type of? Emulsifiers
How do detergent molecules remove the stain? They lift the grease molecule off of the clothing, when you rinse the clothes the oil is pulled away. They are able to pull of the oil due to the strong intermolecular bonds.
Why is dry cleaning different to normal cleaning? It doesn't use water
Why can detergents remove grease stains but normal water can't? The detergents have stronger intermolecular forces with grease molecules than they have with each other and vice versa. However water molecules have stronger forces with other water molecules than they have with grease molecules.
How does biological washing powder work? It contains enzymes which work quickly but not in high temperatures. It removes biological stains such as food stains, blood, faeces etc