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Environmental Chem..
| Question | Answer | |||||||
|---|---|---|---|---|---|---|---|---|
| Distillation is commonly used to separate [] from []. | Ethanol from water. | |||||||
| Distillation process to separate ethanol from water: Step 1 - water and ethanol are | heated, Step 2 - the [] evaporates first, [], then [] | the ethanol evaporates first, cools, then condenses, Step 3 - the [] left [], [[, then []. | the water left evaporates, cools, then condenses. The mixture is heated in a | flask. Ethanol evaporates first as it's boiling point is | lower. The ethanol vapour is then cooled and condensed inside the | condenser to form a [] [] | pure liquid. When all the ethanol has evaporated from the solution, the [] rises and the [] evaporates. | the temperature rises and the water evaporates. |
| This is the sequence of events in distillation: [] → [] → [] → [] | heating → evaporating → cooling → condensing. | |||||||
| "Several [] products are released when fuels burn. | Several waste products are released when fuels burn. These do not just disappear and they can harm the | environment by contributing to global w[], global d[] and [] []. | by contributing to global warming, global dimming and acid rain. | |||||
| Fuels burn when they react with [] in the []. | when they react with oxygen in the air. If there is plenty of air, [] combustion happens. | If there is plenty of air, complete combustion happens. Coal is mostly | carbon. During complete combustion, carbon is [] to carbon dioxide | carbon is oxidised to carbon dioxide: carbon + oxygen → | carbon dioxide. | |||
| Carbon dioxide is a g[]h[] gas. | Carbon dioxide is a greenhouse gas. Increasing [] of it in the atmosphere "contribute to global warming". | Increasing concentrations of it in the atmosphere | ||||||
| Hydrocarbon fuels contain [] and []. | Carbon and Hydrogen. During combustion, hydrogen is [] to water | hydrogen is oxidised to water(remember that water, H2O, is an oxide of | hydrogen). In general: hydrocarbon + oxygen → | carbon dioxide + water. | ||||
| Incomplete combustion: If there is insufficient air for complete combustion, [] combustion (also called [] combustion) happens. | Incomplete combustion (also called (partial combustion) happens. Hydrogen is still oxidised to | water, but instead of Carbon Dioxide, [] [] forms. | Instead of Carbon Dioxide, Carbon Monoxide forms. Carbon monoxide is a t[] gas, so adequate [] is important when burning fuels. | Carbon Monoxide is a toxic gas, so adequate ventilation is important when burning fuels. Solid [] (p[]) are also released | Solid particles (particulates) are also released. These contain | Carbon and are seen as [] or [] | and are seen as smoke or soot. "Particulates cause global dimming. They reduce the amount of sunlight reaching the Earth’s surface." | |
| Acidic oxides: Carbon dioxide dissolves in [] in the [] | Carbon dioxide dissolves in water in the atmosphere to form a weakly [] solution | to form a weakly acidic solution. This means that rainwater is naturally slightly | acidic. However, some of the products from [] fuels make rainwater more [] than normal. | Some of the products from burning fuel make rainwater more acidic than normal. This is [] rain. | This is acid rain. Acid rain reacts with metals and rocks such as l[] | such as limestone, causing damage to buildings and statues. Acid rain also makes rivers and lakes too [] for some aquatic life to survive. | too acidic for some aquatic life to survive. | |
| Acid rain damages the [] layer on the leaves of trees. | Acid rain damages the waxy layer on the leaves of trees. This makes it more difficult for trees to absorb the [] they need for healthy growth and they may die. | to absorb the minerals they need for healthy growth and they may die. | ||||||
| Sulfur dioxide: Coal and most hydrocarbon fuels naturally contain some s[] compounds | some Sulphur compounds. When the fuel burns, the Sulfur it contains is [] to [] | the Sulpur it contains is oxidised to Sulphur dioxide: sulfur + oxygen → | sulfur dioxide This gas dissolves in | water to form an [] solution | to form an acidic solution. "It is a cause of" [] [] | "acid rain." | ||
| Sulfur can be removed from fuels before they are | used. ‘Low []’ petrol and diesel are widely available at filling stations to use in vehicles. | 'Low Sulphur' petro and diesel. In power stations, Sulfur dioxide can be removed from the [] gases before they are released from chimneys. | from the waste gases. The waste gases are treated with p[] l[]. | powdered limestone. The Sulfur dioxide reacts with it to form | calcium sulfate. This can be used to make plasterboard for lining interior walls, so turning a harmful product into a useful one. | |||
| Oxides of nitrogen: At the high temperatures found in an engine or furnace, nitrogen and [] from the air can react together. | Nitrogen and Oxygen. They produce various [] of [] | Oxides of Nitrogen, often called NOx (x ss). "These also cause | acid rain." | |||||
| Acid rain is a major pollution problem. It can be caused by the [] of fuels that contain []. | It can be caused by the combustion of fuels that contain Sulphur. When this Sulphur is burned it produces the a[] gas [] []. | It produces the acidic gas Sulphur Dioxide. Sulphur + Oxygen → Sulphur dioxide Car engines are also responsible for producing the acidic gases. The spark plug in petrol engines has enough energy to break apart stable nitrogen molecules and oxygen mo | to form the acidic gas Nitrogen dioxide. Nitrogen + Oxygen → | Nitrogen dioxide. Both Sulphur dioxide and Nitrogen dioxide will dissolve in r[] w[] | rain water to produce [] [] | acid rain. | ||
| The weathering of rocks by chemicals is called chemical weathering. Rainwater is naturally slightly acidic because [] [] from the air dissolves in it. | Carbon Dioxide from the air dissolves in it. Minerals in rocks may react with the | rainwater, causing the rock to be | weathered. Some types of rock are easily weathered by | chemicals. For example, limestone and chalk are made of a mineral called | Calcium carbonate. When acidic rainwater falls on limestone or chalk, a [] [] happens | chemical reaction happens. New s[] substances are formed in the reaction. | New soluble substances are formed in the reaction. These are [] [] and the rock is []. | These are washed away and the rock is weathered. |
| Some types of rock are not easily weathered by chemicals. For example, granite and gabbro are hard rocks that are weathered only slowly. Still some of their [] do react with the acids in rainwater | some of their minerals do react with acids in rainwater to form new, [] substances | weaker substances that crumble and fall away. | ||||||
| When fossil fuels such as coal, oil and natural gas are burned, [] [] and [] [] escape into the air. | Carbon Dioxide and Sulphur dioxide escape into the air. Acid rain makes chemical weathering happen more | quickly. Buildings and statues made from rock are damaged as a result. This is worse when the rock is limestone rather than granite. Acid rain also kills trees and fish. | ||||||
| Metal carbonates such as calcium carbonate break down when [] strongly. | when heated strongly. This is called [] [] | thermal decomposition. Here are the equations for the thermal decomposition of calcium carbonate: (oa means 'on arrow') | Calcium carbonate → [heat oa] | calcium oxide + carbon dioxide. CaCO3 → [heat oa] | CaO + CO2. Other m[] c[] decompose in the same way. Here are the equations for the [] [] of copper carbonate: | Other metal carbonates decompose in the same way. Here are the equations for the thermal decomposition of copper carbonate: | copper carbonate → [heat oa] [], CuCO3 → [heat oa] [] | copper carbonate → [heat oa] Copper oxide + Carbon dioxide, CuCO3 → [heat oa] CuO + CO2. |
| In the example of Calcium carbonate and Copper carbonate the products are a [] [] and [] [] | the products are a metal oxide and a Carbon dioxide. | |||||||
| The carbon dioxide gas can be detected using l... | limewater. Limewater turns cloudy [] when carbon dioxide is bubbled through it. | turns cloudy white. Metals high up in the reactivity series - such as calcium - have carbonates that need a lot of [] to decompose them. | that need a lot of energy to decompse them. Metals low down in the reactivity series - such as copper - have carbonates that are easily | decomposed. This is why copper carbonate is often used at school to show these reactions. It is easily decomposed, and its colour change, from green copper carbonate to [] copper [], is easy to see | to black copper oxide. | |||
| Limestone is a type of rock, mainly composed of | calcium carbonate. Limestone is quarried (dug out of the ground) and used as a [] material. | building material. It is also used in the manufacture of cement, mortar and concrete. | ||||||
| Carbonates react with acids to produce [], a [] and []. | Carbon dioxide, a salt and water. For example: calcium carbonate + hydrochloric acid → | carbon dioxide + calcium chloride + water; CaCO3 + 2HCl → | CO2 + CaCl2 + H2O | |||||
| Since limestone is mostly | calcium carbonate, it is damaged by [] []. | acid rain. Sodium carbonate, magnesium carbonate, zinc carbonate and copper carbonate also react with acids: when in contact with acids, they | fizz and the carbon dioxide released can be detected using | limewater. | ||||
| When limestone is heated strongly, the calcium carbonate it contains | decomposes to form | calcium oxide. This reacts with water to form | calcium hydroxide, which is an a[] | alkali. Calcium hydroxide is used to [] excess acidity | neutralise excess acidity, for example, in lakes and soils affected by acid rain. | |||
| Cement is made by heating powdered [] with []. | powdered limestone with clay. Cement is an ingredient in mortar and concrete. | |||||||
| Limestone, cement and mortar slowly react with [] [] dissolved in rainwater | Carbon dioxide dissolved in rainwater. | |||||||
| When an acid is dissolved in water we get a solution that's | acidic, and alkalis make [] solutions. | alkaline solution. If a solution is neither acidic nor alkaline we call it | neutral. Pure water is neutral, and so is paraffin. Indicators are substances that, when they are added to acidic or alkaline solutions, change | colour. Two indicators that are commonly used in the laboratory are | Litmus and universal. | |||
| Litmus indicator solution turns red in | acidic solutions and blue in alkaline solutions - and it turns purple in | neutral solutions. Litmus paper is usually more reliable; it comes in red or blue, and has the same colour changes except when the solution is neutral the colour does | not change. | |||||
| Unlike litmus, universal indicator can show us exactly how strongly acidic or alkaline a solution is. Universal indicator has many different colour changes, from red for strong | acids to dark purple for strong | bases. In the middle, neutral pH 7 is indicated by | green. | |||||
| With universal indicator: neutral solutions are exactly PH | 7, acidic solutions have pH values less than | 7; alkaline solutions have pH values more than | 7. | |||||
| A chemical reaction happens if you mix together an [] and a []. | acid and a base. The reaction is called | neutralisation, and if you add just the right amount of acid and base together, what is made is a [] solution | a neutral solution. | |||||
| Metal oxides and metal hydroxides are two types of | bases. For example copper oxide and sodium hydroxide. Here are general word equations for what happens in their neutralisation reactions with acids. metal oxide + acid → | a salt + water; metal hydroxide + acid → | a salt + water. Notice that a salt and water are always produced. The mixture usually warms up a little during the reaction, too. The exact salt made depends upon which [] and [] were used. | which acid and base were used. Carbonates and hydrogen carbonates are two other types of | base. They also make a salt and water when we [] them with []. | When we neutralise them with acid. But this time we get carbon dioxide gas too. The reaction fizzes as bubbles of [] []are given off. This is easy to remember because we see the word 'carbonate' in the chemical names. | bubbles of carbon dioxide are given off. These are the general word equations for what happens: acid + metal carbonate →[] acid + metal hydrogen carbonate → [] | acid + metal carbonate → a salt + water + carbon dioxide; acid + metal hydrogen carbonate → a salt + water + carbon dioxide |
| When an acid is neutralised by a base, what is made is a | salt. But the exact salt made depends upon which [] and [] were used | which acid and base are used. The name of a salt has two parts: the first part comes from the [] in the [] used | comes from the metal in the base used; the second part comes from the [] that was used | the acid. If Hydrochloric acid is used, the second part of the salt's name is | chloride; if Sulphuric acid is used, the second part of the salt's name is | sulphate; if nitric acid is used, the second part of the salt's name is | nitrate. | |
| Carbon dioxide + water → | Carbonic acid; Sulphur dioxide + water → | Sulphuric acid; Nitrogen oxides + water → | nitric acids. CO2+H2O → | H2CO3; SO2 + H2O → | H2SO4; NO2 +H2O → | HNO3. | ||
| Distillation is a process that can be used to separate a [] [] from a [] of []. | pure liquid from a mixture of liquids. It works when the liquids have different [] []. | boiling points. | ||||||
| The alcohol in alcoholic drinks is | ethanol. |
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Toluo
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