Chemistry unit 2 (non-metals)

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Collecting insoluble gases...
The gas which is insoluble in water is out through a delivery tube into a gas jar. The gas then pushes the water out of the gas jar. This is called collection over water.
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Collecting soluble gases...
Gases that are soluble In water are collected by displacement of air and the density of the gas compared to air must be considered.
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What types of gases use downward delivery and which type use upward delivery?
Gases denser than air are collected by downward delivery eg SO2 or HCL. Gases that are less dense than air are collected by upward delivery eg NH3
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What are the physical and chemical properties oh hydrogen?
Hydrogen is a colourless, odourless gas that is insoluble in water and less dense than air. It is diatomic. Hydrogen burns explosively, reduces heated copper oxide and reacts with nitrogen to form ammonia.
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Preparation of hydrogen...
Hydrogen is prepared using zinc or magnesium and dilute hydrochloric acid. Hydrogen is collected over water because it is insoluble in water. The reaction of HCL with Mg is more vigorous and is not recommended for controlled preparation of hydrogen.
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What is the test for hydrogen?
Apply a lighted splint and it will burn with a squeaky pop. Hydrogen is used for meteorological (weather) balloons, rocket engines, and as a clean fuel.
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Hydrogen as a clean fuel...
Hydrogen is described as a 'clean' fuel because the only product of combustion is non-polluting. Hydrogen can be produced from the electrolysis of water and can be used to power vehicles in liquid form. Hydrogen is very flammable so need high safety
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What are the chemical and physical properties of carbon?
Carbon exists as two distinct forms - diamond and graphite. These have identical atoms but it is the way they are bonded that makes the forms different. These different forms are allotropes. Carbon burns to from carbon dioxide/monoxide.
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Preparation of carbon dioxide...
Carbon dioxide is prepared from calcium carbonate and hydrochloric acid. Carbon dioxide is collected over water because it has a low solubility in water.
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What are the physical and chemical properties of carbon dioxide?
Carbon dioxide is a colourless, odourless gas with a low solubility in water. It is denser than air and does not support combustion. CO2 reacts with water to form the weak carbonic acid, with an alkali producing slay and water and burns in Mg.
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What is the test for carbon dioxide?
Bubble the gas through limewater and the colourless solution becomes milky. If it is added in excess the precipitate redid solves to form a colourless solution. It is used in fire extinguishers, making carbonated water and dry ice.
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What are the chemical and physical properties of nitrogen?
Nitrogen is a relatively unreactive gas. The lack of reactivity is because of the triple covalent bond between the nitrogen atoms in N2 molecules. The bond requires substantial energy to break. However it will react with burning Mgto form Mg3N3
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Preparation of nitrogen...
When preparing you must removing carbon dioxide, oxygen, and water vapour from the air. CO2 is removed by bubbling through alkaline solution, O2 is removed by hating over copper and passing the mixture through H2SO4 which acts as a dehydrating agent
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Preparation of nitrogen (2)...
The nitrogen produced is collected over water. It is impure because it contains noble gases but these do not interfere with the reactions of nitrogen because they are inert gases.
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Formation of ammonia (haber process)...
N2 and H2 are mixed in a 1:3 ratio. They are reacted at 450 degrees, a pressure of 200atm and with an iron catalyst. In the equation the double arrow represents a reversible reaction. Only about 10% of nitrogen and hydrogen are converted to ammonia.
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Formation of ammonia (haber process)(2)...
A lower temperature results in a higher yield of ammonia in this industrial process but the lower temperature could cause a lower rate of reaction. 450c is a compromise temperature. Higher Pressure is expensive to apply and is dangerous.
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Uses of nitrogen...
nitrogen has 2 main uses: liquid nitrogen is used as a liquid coolant and in food packaging nitrogen creates inert atmosphere to keep food fresh.
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What are the physical properties of ammonia?
Ammonia NH3 is a colourless, pungent gas that is soluble in water and less dense than air. It forms an alkaline solution and ammonium salts are used as nitrogenous fertilisers.
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Test for ammonia...
Dip a glass rod in concentrated HCL and put this in a sample of the gas. If ammonia is present, a white 'smoke' of ammonium chloride is observed.
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Detecting ammonium compounds...
An ammonium compound can be detected by heating it with a solid alkali metal or an alkaline earth metal hydroxide. Any gas produced can then be tested.
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Advantages and disadvantages of nitrogenous fertilisers...
It causes the leaching of nitrates into rivers which leads to eutrophication. Nitrates in drinking water can also lead to blue-baby syndrome. However without them there would not be enough food as plants grow faster and larger.
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What are the chemical and physical properties of oxygen?
Oxygen is a colourless, odourless gas that is only slightly soluble in water and is slightly denser than air. It reacts with hydrogen,carbon, sulfur,magnesium,zinc, iron and copper.
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What are the chemical and physical properties of sulfur?
Sulfur is a brittle, yellow solid. Sulfur melts to a red liquid, burns with a blue flame producing a colourless pungent gas. When reacting with iron the mixture glows red when heated, forming a black solid.
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What are the allotropes of sulfur?
Sulfur exists as three allotropes: rhombic sulfur, monoclinic sulfur and plastic sulfur. Allotropes are different forms of the same element in the same physical state.
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What are the physical and chemical properties of sulfur dioxide?
SO2 is a colourless, pungent gas that is soluble in water and denser than air. It reacts with water to form the weak acid sulfurous acid (acid rain). It is also an acidic oxide and reacts with alkalis forming salt and water.
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the contact process(1)...
stage 1 is the combustion of sulfur to form sulfur dioxide. stae 2 is the catalytic production of sulfur trioxide. the SO2 is mixed with air at 450c and 2atm in the presence of vanadium oxide catalyst.
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the contact process(2)...
stage 3 is absorption in cncetrated sulfuric acid. the sulfur trioxide is dissolved in concentrated H2SO4 to form oleum, H2S2O7. In stage 4 the oleum is diluted in water to form concentrated H2SO4.
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the contact process(notes)...
SO3 is notdiretly mised with water beause the reaction is to exothermic and produces a corrosive mist. At stage 2 450c is a compromise temperature as a lower temperature results in a higher yield but also lower rate of reaction.
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what are the chemical properties of dilute sulfuric acid?
dilute SO4 is a typicl acid, reacting with metals, metal oxides, metal hydoxides, metal carbonates and ammonia. it is used in car batteries and th manufacture of fertilisers.
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what are the chemical properties of concentrated sulfuric acid?
concentrated H2SO4 dehydrates to form carbon and water vapor. there is a pungent odour as the sugar swells, a black solid forms. concentrated H2SO4 changes hydrated CuSO4 from blue to white as again it acts as a dehydrating agent.
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describe how to dilute concentrated sulfuric acid...
when diluting concentrated H2SO4 a large amount of heat is evolved, so the acid should be added slowly to a large amount of water with stirring to prevent too much heat being produced. concentrated H2SO4 is corrosive and water must not be added to it
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Card 2

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Collecting soluble gases...

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Gases that are soluble In water are collected by displacement of air and the density of the gas compared to air must be considered.

Card 3

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What types of gases use downward delivery and which type use upward delivery?

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Preview of the front of card 3

Card 4

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What are the physical and chemical properties oh hydrogen?

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Card 5

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Preparation of hydrogen...

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