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13 Cards in this Set
- Front
- Back
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How do we separate gases in air? |
Fractional distillation. |
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How does fractional distillation work? |
Air must be cooled into a liquid so the temperature is set to below -200°C. The gaseous air is compressed to 150 times atmospheric pressure. This warms the air up so it is cooled to normal temperatures by passing the air over pipes carrying cold water. The pressure is released which allows the air to expand rapidly and cools the temperature so the gases condense to liquids. Carbon dioxide and water are removed from the mixture since they are solids. The column is colder at the top so nitrogen boils first and is passed out of the top of the column as a gas. The bottom is -185°C so oxygen is still a liquid and is separated from the bottom. The argon can be collected below the nitrogen but above the oxygen. |
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What are nitrogen and oxygen used for? |
Liquid nitrogen cools things to very low temperatures. Nitrogen gas is unreactive and can be used to stop food going off. It can also be used on oil tankers to reduce the risk of explosion. Nitrogen gas can make ammonia which can be converted into fertilisers. Oxygen helps people breathe and can make things react. |
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What is a test for oxygen? |
A glowing splint will relight in oxygen. |
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When metallic elements burn what do they produce? |
Solid oxides. For example 2Mg(s) + O2(g)--> 2MgO (s) |
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When non-metallic elements what do they form? |
Oxides which are produced as gases. For example C(s) + O2(g) --> CO2(g) |
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If a metal oxide dissolves in water, does it make an acidicic or alkaline solution? |
Alkaline. Insoluble metal oxides are called bases. |
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If a non-metal oxide dissolves in water, does it make an acidicic or alkaline solution? |
Acidic. Some are neutral. |
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Metal oxides are ... Non-metal oxides are ... |
Alkaline Acidic (some are neutral) |
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How do filter jugs work? |
The carbon reduces the levels of chlorine left in the water, as well as pesticides and other organic impurities. The ion-exchange resin removes calcium, magnesium, lead, copper, and aluminium ions. Silver nanoparticles discourage the growth of bacteria within the filter. |
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What is rusting? |
The corrosion of iron. Both air and water are needed. iron + oxygen + water --> hydrated iron(ii) oxide |
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How do we prevent rust? |
Coat the iron or steel with: paint oil or grease plastic a less reactive metal a more reactive metal |
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What is galvanisation? |
When zinc (a more reactive element) is used to coat the iron so any water or oxygen reacts with the zinc instead of iron. This is called sacrificial protection. Even if the coating is scratched the iron does not rust. |
