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39 Cards in this Set
- Front
- Back
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What is electrolysis? |
Flow of charge by moving ions that discharge at electrodes. |
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The reaction at the cathode is written as: (half equation) |
Na+ + e- --> Na |
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In electrolysis of sodium chloride, what goes to the cathode? |
Sodium. Na+. |
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If sodium hydroxide is electrolysed, what is produced at the cathode and the anode? |
Hydrogen at cathode Oxygen at anode |
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If copper sulfate is electrolysed, what is formed at the anode and cathode? |
Cathode: copper Anode: oxygen |
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How can you increase the yield of products from electrolysis? |
Increase time and current |
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Why are fuel cells used in space crafts? |
-What is produced so they can drink it -Lightweight -Compact -No moving parts |
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Why are fuel cells good for car use? |
-Don't produce any CO2 directly -Alternative to the nonrenewable fossil fuels -Main product is water which isn't polluting -Large source of hydrogen readily available -Weigh less than car batteries |
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What's good about hydrogen-oxygen fuel cells? |
-Direct energy transfer so less wasted -Less polluting -Last longer than regular batteries -Weigh less than car batteries |
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What's bad about hydrogen-oxygen fuel cells? |
-Poisonous catalysts used that have to be disposed of at the end of life -Fossil fuels are burnt to produce hydrogen and oxygen needed |
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What's the symbol equation for what takes place in a hydrogen oxygen fuel cell? |
2H2 + O2 --> 2H2O |
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What is a redox reaction? Give an example. |
One where electrons are both lost and gained. Rusting is one. |
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Whats the word equation for rusting? |
iron + oxygen + water --> hydrated iron(III) oxide |
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How does galvanisation prevent rusting? |
Covering in a layer of zinc stops water and oxygen from reaching iron's surface. It's also a sacrificial metal: it's more reactive than iron. |
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What does an oxidising agent do? |
Take electrons away from a substance. |
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What does a reducing agent do? |
Pushes electrons onto a substance. |
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Put these in order of reactivity from least to most. zinc, iron, tin, magnesium |
Tin
Iron Zinc Magnesium |
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What is the word equation for fermentation? |
glucose --> ethanol + carbon dioxide |
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What happens if air is present during fermentation? |
Ethanoic acid is produced, not ethanol |
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What is the word equation for a hydration reaction? |
ethene + water --> ethanol |
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What happens during hydration? |
Ethene and steam are passed over a hot phosphoric catalyst. |
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Which is better: hydration or fermentation? |
Fermentation is sustainable, uses less energy BUT is batch and needs fractional distillation. Hydration needs more energy, is from a finite resource but has high yield and is continuous. Hmmmm |
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What have CFCs been replaced with? |
HFCs and alkanes |
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How does the ozone absorb UV? |
UV has exactly the right frequency to make ozone molecules vibrate so radiation converts to movement energy inside each molecule. |
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git gud |
never |
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How do CFCs deplete the ozone layer? |
Sun breaks down CFCs into chlorine radicals- causing a chain reaction- and these then react with ozone and turn it back to oxygen gas. The chlorine atoms are then regenerated to do it all again. |
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Why are CFCs still depleting the ozone right now even though they're banned? |
They last 20-50 years before they're broken down by UV radiation. |
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How is permanent hardness in water created? |
When calcium sulfate rock dissolves into water |
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How is temporary hardness formed? |
Calcium hydrocarbonate in water |
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What's the equation for temporary hard water? |
calcium carbonate + carbon dioxide + water --> calcium hydrocarbonate |
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What happens when a soap flake is shaken in water? |
Calcium ions react with soap to turn in to scum. More flakes are added until all calcium ions have been reacted with- then a lather can be produced. |
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How is temporary hardness removed? |
Boiling as calcium hydrogencarbonate decomposes in hot water to form calcium carbonate (limescale), water and CO2. |
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How is permanent hardness removed? |
Ion exchange resins. Solid beads of resin trap calcium ions and exchange them for sodium ions. |
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How does washing soda affect hardness of water? |
When it dissolves, it reacts with calcium sulfate in water to form insoluble calcium carbonate- thus 'locking up' the calcium ions. |
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What is the test for unsaturation in oil? |
It's shaken with bromine water which is orange. If unsaturated, the solution became colourless. |
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What is an industrial use of vegetable oil? |
Making margarine. |
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How do you harden an oil? |
Hydrogen bubbles through the oil at 200 degrees C using a nickel catalyst. The hydrogen reacts with the C=C bonds and turns them into single bonds. |
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What does polyunsaturated mean? |
Compound contains more than one C=C bond. |
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What kind of reaction is bromine with a C=C bond? |
An addition reaction. |
