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112 Cards in this Set
- Front
- Back
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Become familiar with simple diffusion experiments. |
Okay. |
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Why isn't the percentage yield always 100%? |
The reaction may not go to completion because it is reversible. Some of the product may be lost when separated from the reaction mixture. Some of the reactants may react in ways different from the expected reaction. |
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What is an ionic compound? |
Ionic compounds have regular structures (giant ionic lattices) in which there are strong forces of attraction in all directions between oppositely charged ions. |
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Why is diamond hard but graphite is soft? |
In diamond, each carbon atom forms four covalent bonds with other carbon atoms in a giant covalent structure. In graphite, each carbon atom bonds to three others, forming layers. The layers are free to slide over each other since there are no covalent bonds between layers so graphite is soft and slippery. |
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What can fullerenes be used for? |
Drug delivery into the body, in lubricants, as catalysts, and in nanotubes for reinforcing materials. |
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What is the structure of fullerenes like? |
They are based on hexagonal rings of carbon atoms. |
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How small are nanoscience structures? |
1-100 nm in size, of the order of a few hundred atoms. |
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What is different about nanoparticles? |
They have different properties from those for the same materials in bulk and have a high surface area to volume ratio, which may lead to the development of new computers, new catalysts, new coatings, highly sensitive sensors, stronger and lighter construction materials, and new cosmetics such as suntan cream and deodorants.
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What is the approximate composition of air in terms of percentages of oxygen and nitrogen? |
Nitrogen: 78% Oxygen: 21% |
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How are oxygen and nitrogen obtained from air. |
Dry air, free from carbon dioxide, can be liquefied and then fractionally distilled to obtain oxygen and nitrogen. |
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Describe the combustion of sodium. |
Sodium burns with an orange flame to form sodium oxide. |
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Describe the combustion of magnesium. |
Magnesium burns with a very bright light to form magnesium oxide. |
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How does carbon monoxide, sulphur dioxide, oxides of nitrogen, carbon dioxide, and solid carbon particles arise and what effects do they have? |
When there isn't enough oxygen inside an engine, we get incomplete combustion so instead of carbon becoming carbon dioxide, it turns into carbon monoxide gas (CO). It is a toxic gas. All fossil fuels contain some sulphur. This reacts with oxygen when we burn the fuel, forming sulphur dioxide. This gas is toxic and is a cause of acid rain, which damages trees. It also kills animal life in lakes. High temperatures in an engine allow the nitrogen and oxygen in the air to react. This makes nitrogen oxides, which are toxic and can trigger some people's asthma. They also cause acid rain. Carbon dioxide is the result of burning fuels. This results in climate change. Carbon particles are soot, they may be released when fuels are burnt and cause global dimming. |
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Be aware of desalination and obtaining pure water. |
I am aware. |
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Why does drinking water have low levels of dissolved salts and microbes? |
Water is passed from a suitable source through filter beds to remove solids. It is then sterilised with chlorine. |
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How do water filters work? |
Water filters containing carbon, silver and ion exchange resins can remove some dissolved substances from tap water to improve the taste and quality. |
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Be aware of arguments for and against the addition of fluoride to drinking water. |
I am aware. |
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What is necessary for iron to rust? |
Both air and water. |
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How do you prevent rusting? |
Greasing, painting, sacrificial protection (e.g. galvanising). |
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What are trends in Group 1? |
They are metals with low density (first three are less dense than water). They react with non-metals to form ionic compounds in which the metal ion carries a charge of +1. The compounds are white solids that dissolve in water to form colourless solutions. They react with water, releasing hydrogen. They form hydroxides that dissolve in water to give alkaline solutions. The further down the group the element is, the more reactive it is. |
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What are trends in the transition elements? |
They have higher melting points (except mercury) and higher densities. They are stronger and harder. They are much less reactive so do not react as vigorously with water or oxygen. |
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What are trends in Group 7? |
They react with metals to form ionic compounds in which the halide ion carries a charge of -1. The further down the group an element is, the less reactive it is and the higher the melting and boiling points. A more reactive halogen can displace a less reactive one from an aqueous solution of its salt. |
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How can the trends in reactivity within groups of the periodic table be explained? |
The higher the energy level of the outer electrons, the more easily electrons are lost and the less easily electrons are gained. |
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What are bases and alkalis? |
Metal oxides and hydroxides are bases. Soluble hydroxides are alkalis. |
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What do acids react with bases to form and what is this type of reaction called? |
Salts, this is called a neutralisation reaction. |
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Ammonia dissolves in water to form in an (acidic/alkaline) solution. Why are ammonium salts important? |
Alkaline. They are fertilisers. |
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A solution of calcium hydroxide in water (limewater) reacts with carbon dioxide to form what? |
Calcium carbonate. |
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What is a test for carbon dioxide? |
Carbon dioxide turns limewater cloudy. |
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H^+ (aq) ions form ... and OH^- (aq) ions form .... |
Acids Alkalis |
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What happens in a neutralisation reaction?
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H^+ (aq) + OH^- (aq) --> H2O (l) |
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Learn how to carry out titrations using strong acids and strong alkalis only (sulphuric, hydrochloric, and nitric acids only). |
Okay. |
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Soluble salts can be made from acids by reaction them with ... ? |
Metals, though some are too reactive or not reactive enough. Insoluble bases, the base is added to the acid until no more will react and the excess solid is filtered off. Alkalis, an indicator can be used to show when the acid and alkali have completely reacted to produce a salt solution. |
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Salt solutions can be ... to produce solid salts. |
Crystallised. You do this by evaporating it. |
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How do you make insoluble salts? |
Mixing appropriate solutions of ions so that a precipitate is formed. Precipitation can be used to remove unwanted ions from solutions: for example, in treating water for drinking or in treating effluent. |
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The carbonates of which metals decompose on heating (thermal decomposition) in a similar way?
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Magnesium, copper, zinc, calcium, and lithium. |
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What do metal carbonates react with acids to produce? |
Carbon dioxide, a salt, and water. |
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Tell me about limestone. |
Limestone, containing the compound calcium carbonate (CaCO3), is quarried and can be used as a building material, or powdered and used to control acidity in the soil. It can be used in the manufacture of cement, glass, and iron to produce calcium oxide (lime). |
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Put the metals you need to know about in the reactivity series as well as hydrogen and carbon. |
Potassium, sodium, lithium, calcium, magnesium, (carbon), zinc, iron, (hydrogen), copper. |
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How do you establish positions within the reactivity series?
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Displacement reactions involving metals and their compounds in aqueous solution establish positions. The non-metals are included based on the reactions of metals with dilute acids (hydrogen), and of metal oxides with carbon. |
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How can copper be obtained from solutions of copper salts? |
By displacing it using scrap iron. |
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What is the test for hydrogen? |
A lit splint gives a squeaky pop. |
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How are metals less reactive than carbon extracted from their oxides? |
Reduction with carbon. |
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How are metals more reactive than carbon extracted from their oxides and what makes them expensive? |
Electrolysis of molten compounds. The use of large amounts of energy in the extraction of these metals makes them expensive. |
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How can copper by extracted from copper-rich ores? |
Heating the ores in a furnace (smelting). The copper can be purified by electrolysis. |
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Why are we using new ways of extracting copper from low-grade ores? |
The supply of copper-rich ores is limited and is being depleted. Traditional mining and extraction have major environmental impacts. New ways are being researched to limit the environmental impact of traditional mining. |
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Copper can be extracted by phytomining, or by bioleaching. How do these processes work?
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Phytomining uses plants to absorb metal compounds and the plants are burned to produce ash that contains the metal compounds. Bioleaching uses bacteria to produce leachate solutions that contain metal compounds. |
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How can copper be obtained from solutions of copper salts? |
Electrolysis. The positive electrode (anode) is made from impure copper and the negative electrode (cathode) is made from pure copper. These are the half equations: Anode - Cu --> Cu^2+ + 2e^- (oxidation) Cathode - Cu^2+ + 2e^- --> Cu (reduction) Displacement using scrap iron also works. iron + copper sulphate --> iron sulphate + copper |
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Why should we recycle materials? |
Extracting them uses limited resources, and is expensive in terms of energy and in terms of effects on the environment. |
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Describe metallic bonding. |
Metals consist of giant structures of atoms arranged in a regular pattern. The outer shell electrons are delocalised and can more through the whole structure. This corresponds to a structure of positive ions with electrons between the ions holding them together by strong electrostatic attractions. |
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Why do metals conduct heat and electricity? |
Because the delocalised electrons in their structures can move throughout the metal. |
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Why are metals able to be bent and shaped? |
The layers of atoms in metals are able to slide over each other. |
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Why are alloys harder than pure metals? |
They are made from two or more metals. The different sizes of atoms in the metals distort the layers in the structure, making it difficult for them to slide over each other. |
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What are shape memory alloys? What is an example? |
Shape memory alloys can return to their original shape after being deformed. An example is Nitinol, which is used in dental braces. |
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Why is iron from a blast furnace brittle? |
It contains about 96% iron and the impurities make it brittle so it has limited uses. |
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What are the properties of low-carbon, high-carbon, and stainless steels? |
Low-carbon - Easily shaped High-carbon - Hard Stainless - Resistant to corrosion |
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What properties of copper makes it useful for electrical wiring and plumbing? |
It is a good conductor of electricity and heat. It can be bent but is hard enough to be used to make pipes or tanks. It does not react with water. |
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What is activation energy? |
The minimum amount of energy that particles must have to react. |
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How do you increase the rate of reaction and why does it work? |
Increase temperature, this increases the speed of the reacting particles so they collide more frequently and more energetically. Increase pressure in gases, this increases the frequency of collisions. Increase concentration in solutions, this increases the frequency of collisions. Increase surface area in solids, this increases the frequency of collisions. Use catalysts. |
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Why are catalysts used in industrial processes? |
To reduce costs. |
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What is crude oil? |
A mixture of a very large number of compounds, most of which are hydrocarbons (contain only hydrogen and carbon atoms). |
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How can the hydrocarbons in oil be separated into fractions? |
Each fraction contains molecules with a similar number of carbon atoms. You can separate them by evaporating the oil and allowing it to condense at different temperatures in a fractionating column. This is called fractional distillation. |
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What prefixes correspond to how many carbon atoms there are in alkanes, alkenes, alcohols, carboxylic acids, and esters? |
Meth - 1
Prop - 3 But - 4 Pent - 5 Then it carries on as you'd expect |
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What is the general formula for alkanes?
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CnH2n+2 |
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What are saturated hydrocarbons? |
Hydrocarbons in which all the carbon-carbon bonds are single covalent bonds. |
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How does the size of alkanes affect boiling points, viscosity, and flammability? |
As the alkane molecules get bigger:
The boiling point increases, The viscosity increases (they flow less easily). Lower flammability (they ignite less easily). |
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When can sulphur be removed from fuels?
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Sulphur can be removed before they are burned burned (e.g. in vehicles). Sulphur dioxide can be removed from the waste gases after combustion (e.g. in power stations). |
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What are the benefits and disadvantages of biofuel? |
They use renewable resources. They are theoretically carbon neutral. The demand for biofuel crops means greater demand on rainforest land. |
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How do you use ethanol as a biofuel? |
It is produced from a dilute solution of ethanol obtained by the fermentation of plant materials at a temperature between 20°C and 35°C. In fermentation, sugar is converted into ethanol and carbon dioxide if conditions are anaerobic. Yeast is used since they contain enzymes that are natural catalysts for making this process happen. |
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How can hydrogen be used as a fuel and what are the advantages and disadvantages? |
It can be burned as a fuel in combustion engines or used in fuel cells that produce electricity to power vehicles. The advantages are that the only product formed is water and the fuel cells are very efficient, but the disadvantages are that to generate hydrogen water must be electrolysed which requires electricity (which is generated by burning fossil fuels), and there are few filling stations that sell hydrogen. |
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What are the conditions required for cracking? |
Heated to vaporise them. A hot catalyst or mixed with steam and heated to a very high temperatures so thermal decomposition can occur. |
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What is the general formula for alkenes? |
CnH2n They always have one double carbon-carbon bond. |
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What is the test for alkenes? |
They turn bromine water colourless from orange. |
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What are some of the products of cracking useful for? |
Fuels. |
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How can ethanol be produced with ethene? |
By reacting ethene with steam in the presence of a catalyst. |
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What happens in polymerisitation reactions? |
Many small molecules (monomers) join together to form very large molecules (polymers). |
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Why are low-density and high-density polyethane different? |
They are produced using different catalysts and reaction conditions. |
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What are thermosoftening and thermosetting polymers? |
Thermosoftening polymers consist of individual, tangled polymer chains. Thermosetting polymers consist of polymer chains with cross-links between them so they do not melt when heated. This cross links are strong covalent bonds which are not easily broken, but the forces between the tangled polymer chains are weak intermolecular forces which are easily broken. |
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What are useful applications of polymers? |
New packaging materials, waterproof coatings for fabrics, dental polymers, wound dressings, hydrogels, and smart materials (including shape memory polymers). |
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Why can polymers lead to problems with waste disposal? |
They aren't biodegradable. |
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What are biodegradable plastics made from? |
Cornstarch. |
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What is the formula for ethanol? |
CH3CH2OH or C2H6O They have the functional group -OH. |
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What are the properties of methanol, ethanol, and propanol? |
They dissolve in water to form a neutral solution. They react with sodium to produce hydrogen. They burn in air. They are used as fuels and solvents, and ethanol is the main alcohol in alcoholic drinks. |
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How can ethanol be oxidised, what does it form, and what is it used for? |
It forms ethanoic acid. It can be oxidised either by adding chemical oxidising agents or by microbial action. Ethanoic acid is the main acid in vinegar, which is an aqueous solution that contains ethanoic acid. |
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What is the formula for ethanoic acid? |
CH3COOH Carboxylic acids have the functional group -COOH where the C at the end is bonded to a C, double bonded to an O, and single bonded to an O which is bonded to a H. |
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What are the properties of carboxylic acids, such as methanoic acid, ethanoic acid, and propanoic acid? |
They dissolve in water to produce acidic solutions. They react with carbonates to produce carbon dioxide. They react with alcohols in the presence of an acid catalyst to produce esters. They do not ionise completely when dissolved in water and so are weak acids. Aqueous solutions of weak acids have a higher pH value than aqueous solutions of strong acids with the same concentration. |
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What is the formula for methyl ethanoate? |
CH3COOCH2CH3 Esters have the functional group -COO-. The C is bonded to the end of the 'methyl' part. It has a double bond to an O which is otherwise on its own. It has a single bond to another O which is bonded to a C from the 'ethonoate' part. |
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What are properties of esters? |
They are volatile compounds with distinctive smells and are used as flavourings and perfumes. |
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What are exothermic and endothermic reactions? Give examples and uses as well. |
An exothermic reaction transfers energy to the surroundings, examples include combustion, many oxidisation reactions, and neutralisation. They can be used in self-heating cans (e.g. for coffee) and hand warmers. An endothermic reaction takes in energy from the surroundings, examples include thermal decompositions. Some sports injury packs are based upon endothermic reactions. Energy must be supplied to break bonds, and is released when bonds are formed. In endothermic reactions the energy needed to break existing bonds is greater than the energy released from forming new bonds. |
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What do catalysts do? |
Provide a different pathway for a chemical reaction that has a lower activation energy. |
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What are the draw materials for the Haber process? How are they obtained? |
Nitrogen is obtained from the air and hydrogen from natural gas or other sources. |
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What conditions are used in the Haber process and what does the reaction form? |
A high temperature (450°C) and a high pressure (200 atmospheres). Some of the hydrogen and nitrogen reacts to form ammonia. |
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How is ammonia removed from the Haber process? |
On cooling, the ammonia liquefies and is removed. The remaining hydrogen and nitrogen are recycled. |
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What is equilibrium? |
When a reversible reaction occurs in a closed system, equilibrium is reached when the reactions occur at exactly the same rate in each direction. |
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In a reversible reaction at equilibrium, what happens if the temperature changes? |
If raised: The yield from the endothermic reaction increases. The yield from the exothermic reaction decreases. If lowered: The yield from the endothermic reaction decreases. The yield from the exothermic reaction increases. |
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In a gaseous reversible reaction at equilibrium, what happens if the pressure changes? |
An increase in pressure favours the reaction that produces the least number of molecules as shown by the symbol equation for the reaction. A decrease in pressure favours the reaction that produces the greatest number of molecules as shown by the symbol equation for that reaction. |
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Why do ionic substances conduct electricity when molten or in solution? |
The ions are free to move about in the liquid or solution.
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What is electrolysis? |
When you pass electric current through ionic substances that are molten or in solution and break them down into elements. The substance broken down is called the electrolyte. |
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How is aluminium manufactured by electrolysis? |
In a molten mixture of aluminium oxide and cryolite (which lowers the melting point). Aluminium forms at the negative electrode and oxygen at the positive electrode. The positive electrode is made from carbon, which reacts with the oxygen to produce carbon dioxides. Large amounts of energy are needed for this process. |
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Describe the electrolysis of sodium chloride. Why are the products important? |
It produces hydrogen and chlorine. Sodium hydroxide is also produced. Sodium hydroxide is used for the production of soap and chlorine is used for the production of bleach and plastics. |
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How do you know what is produced at the negative electrode in a solution? |
The metal will be produced if it's less reactive then hydrogen, otherwise hydrogen will be produced. |
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How do you know what is produced at the positive electrode in a solution? |
Oxygen gas from OH^- ions is usually formed unless the solution has a reasonably high concentration of a halide ion. In this case the halide ion is discharged and the halogen formed. The gases are always formed as O2, F2, etc. |
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How can you identify metal ions? |
With a flame test. Lithium compounds result in a crimson flame. Sodium compounds result in a yellow flame. Potassium compounds result in a lilac flame. Calcium compounds result in a red flame. Barium compounds result in a green flame. |
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How can you identify some positive ions? |
Reactions with sodium hydroxide solution. Aluminium, calcium, and magnesium all form white precipitates, but only the aluminium hydroxide precipitate dissolves in excess sodium hydroxide solution. Copper(II) forms a blue precipitate. Iron(II) forms a green precipitate. Iron(III) forms a brown precipitate. |
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What is a test for carbonates? |
They react with dilute acids to form carbon dioxide, which can be tested for using limewater. |
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How can you identify halide ions? |
Add silver nitrate solution and dilute nitric acid. Silver chloride turns white. Silver bromide turns cream. Silver iodide turns yellow. |
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How can you test for sulphate ions? |
In solution, they produce a white precipitate with barium chloride solution the presence of hydrochloric acid.
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How can you separate mixtures? |
Distillation, filtration, and crystallisation. |
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How can you analyse substances present in a solution (e.g. food colourings and inks/dyes)? |
Paper chromatography. |
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How do you carry out a paper chromatography separation? |
Some compounds in a mixture will dissolve better than others in the chosen solvent (which doesn't have to be water). A capillary tube is used to dab a spot of the solution on a pencil line near the bottom of a sheet of absorbent chromatography paper. It is then placed in a solvent at the bottom of a beaker or tank. The solvent is allowed to soak up the paper, running past the spot of mixture. The more soluble a substance is, the further it is carried up. |
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How can you identify Rf values? |
The retention factor value is a ratio, calculated by dividing the distance the spot travels up the paper by the distance the solvent front travels. |
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Why is it better to detect and identify compounds using instrumental methods? |
They are accurate, sensitive, and rapid. They are particularly useful when the amount of a sample is low. |
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What is an example of an instrumental method of detecting and identifying compounds? |
Gas chromatography linked to mass spectrometry.
Gas chromatography allows the separation of a mixture of compounds. This is done because different substances, carried by a gas, travel through a column packed with a solid material at different speeds, so they become separated. The time taken for a substance to travel through the column can help identify the substance. The number of peaks on the output of a gas chromatograph shows the number of compounds present. The position of the peeks on the output indicates the retention time. The output can be linked to a mass spectrometer, which can be used to identify substances leaving the end of the column. It can identify very small amounts very quickly and accurately. It can also give the relative molecular mass of each of the substances separated in the column. The molecular mass is given by the molecular ion peak. |
