AQA AS Chemistry Unit 2 Chemistry in Action – Flashcards
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| By what name is calcium silicate better known? |
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| Slag |
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| State the meaning of the term catalyst. |
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| Substance which speeds up a reaction but is chemically unchanged at the end |
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| Define enthalpy change. |
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| Change in heat content at constant pressure |
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| Define enthalpy. |
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| A measure of the heat content of a substance. |
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| Define mean bond enthalpy. |
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| The enthalpy required to break a covalent bond, averaged over a wide range of compounds |
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| Define standard enthalpy change of combustion. |
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| Enthalpy change when 1 mole of a substance is completely burned in oxygen with all reactants and products in standard states under standard conditions |
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| Define standard enthalpy change of formation. |
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| Enthalpy change when 1 mole of a substance is formed from its constituent elements with all reactants and products in standard states under standard conditions. |
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| Describe a test for sulphate ions. |
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| Add nitric/hydrochloric acid to remove carbonate ions; add barium chloride; a white precipitate of barium sulphate is produced: BaCl2(aq) + SO42-(aq) => BaSO4(s) + 2Cl-(aq) |
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| Describe conditions for the dehydration of an alcohol. What are the products? |
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| Excess heated sulfuric acid; vapours passed over aluminium oxide at 600K. Products are an alkene and water |
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| Describe how you could use a solution of NH3 to distinguish between the solid silver halides. |
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| AgCl dissolves in dilute ammonia; AgBr dissolves in concentrated ammonia; AgI is insoluble in concentrated ammonia |
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| Describe how you could use AgNO3 and HNO3 to distinguish between fluoride, chloride, bromide and iodide ions. |
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| Add nitric acid to remove carbonate or hydroxide ions; add silver nitrate: =>AgF produces no precipitate; =>AgCl produces a white precipitate; =>AgBr produces a cream precipitate; =>AgI produces a pale yellow precipitate. |
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| Describe the Fehling's test for distinguishing between an aldehyde and a ketone. |
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| Warm with Fehling's reagent (containing blue copper(ii) ions); aldehyde will reduce the ions to brick-red copper (i) ions; no observation with ketone |
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| Describe the oxidation of a primary alcohol with excess oxidising agent and reflux, giving the intermediate and the oxidising agent. |
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| Primary alcohol => Aldehyde => Carboxylic acid. Oxidising agent is acidified potassium dichromate(vi). |
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| Describe the Tollens' test for distinguishing between an aldehyde and a ketone. |
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| Warm with Tollens' reagent; aldehyde will reduce it to form a deposit of metallic silver; no observation with a ketone |
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| Describe the trend in reactivity with water going down group II from magnesium to radium. |
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| Reactivity increases; magnesium reacts slowly with cold water but readily with steam; others react readily with cold water; vigour of reaction increases down the group. |
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| Explain why a catalyst has no effect on the position of an equilibrium. |
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| It speeds up both the forward and reverse reactions, and the increase in rate is equal. |
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| Explain why a small increase in temperature has a large effect on the initial rate of a reaction. |
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| Significant increase in the number of molecules with activation energy or above, and molecules have more kinetic energy, so there are many more successful collisions per unit time. (Beware as mark scheme will insist on a sense of scale - you must state that there are many more collisions per unit time) |
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| Explain why fluorine free radicals are not formed by the breakdown in UV light of chlorodifluoromethane, but chlorine free radicals are. |
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| C-F bond enthalpy is too high/bond is too strong to be broken by UV light - C-Cl bond enthalpy is lower/bond is weaker |
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| Explain why the RAM value calculated from a mass spectrum may be slightly different from the value given in the periodic table. |
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| The RAM value in the periodic table takes into account different amounts of isotopes |
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| Give a general equation for the reaction of an alkaline earth metal with water, using M as the metal. |
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| M(s) + 2H2O(l) => M(OH)2(aq/s) + H2(g) |
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| Give a symbol equation for the reaction of chlorine with sodium hydroxide. |
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| Cl2(g) + 2NaOH(aq) => NaClO(aq) + NaCl(aq) + H2O(l) |
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| Give a word equation for the reaction of bromoethane with potassium hydroxide in ethanol. |
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| Bromoethane + potassium hydroxide => ethene + potassium bromide + water |
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| Give a word equation to show the reaction of 1-chloropropane with potassium cyanide. |
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| 1-chloropropane + potassium cyanide => butanenitrile + potassium chloride |
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| Give a word equation to show the reaction of bromoethane with sodium hydroxide in aqueous conditions. What type of reaction is this? |
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| Bromoethane + sodium hydroxide => Ethanol + sodium bromide (nucleophilic substitution) |
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| Give an equation and conditions for the conversion of titanium dioxide into titanium tetrachloride. Why is this conversion necessary? |
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| TiO2 + 2Cl2 + 2C => TiCl4 + 2CO at 900oC. TiCl4 is a liquid so it can be purified by distillation before reduction with an active metal. |
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| Give an equation and conditions for the reduction of titanium tetrachloride by sodium. What other metal can be used as a reducing agent? What are the main costs of this process? |
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| (i) TiCl4 + 4Na => Ti + 4NaCl (ii) Argon atmosphere, 1000oC (iii) Magnesium (iv) Costs of temperature, active metal, argon, batch process |
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| Give an equation and temperature for the industrial extraction of tungsten from its ore. |
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| WO3 + 3H2 => W + 3H2O |
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| Give an equation for the initiation reaction of the chlorination of methane. |
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| Cl2=>2Cl. |
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| Give an equation for the reduction of manganese(IV) oxide with carbon. |
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| MnO2 + C => Mn + CO2 |
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| Give an equation to show how you can find a standard enthalpy of formation given all the standard combustion enthalpy data. |
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| ?H=??Hc(reactants)-??Hc(products) |
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| Give an equation to show how you can find the enthalpy change of a reaction given all the standard formation enthalpy data. |
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| ?H=??Hf(products)-??Hf(reactants) |
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| Give an equation to show the reaction of chlorine with water. |
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| Cl2(g)+H2O(l)<=>HClO(aq)+HCl(aq) |
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| Give an equation to show the reaction of sodium chlorate with water. |
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| NaClO(s)+H2O(l) <=> NaOH(aq) + HClO(aq) |
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| Give an equation to show the reaction of sodium chloride with sulphuric acid. What type of reaction is this? |
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| NaCl(s)+ H2SO4(aq) => NaHSO4(s) + HCl(g) |
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| Give an essential condition for an alkene to exhibit geometric isomerism. |
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| Each of the double bond carbons must have two different groups attached (e.g. a hydrogen and an alkyl, or two alkyl groups of different lengths) |
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| Give four methods of metal extraction. What do they all involve? |
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| Reduction with carbon; reduction by electrolysis; reduction by active metal; reduction by hydrogen. All involve reduction of the metal ions |
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| Give four reasons why metals should be recycled. |
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| To save resources; to create less waste (e.g. from mining); to save energy resources (less energy to recycle than to extract); to reduce air pollution |
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| Give four uses of ethanol. |
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| Used as a solvent in cosmetics; intermediate in production of other organic chemicals; fuel; alcohol |
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| Give one risk associated with the use of hydrogen gas. |
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| It ignites easily/is explosive |
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| Give three equations for the termination reactions of the chlorination of methane. |
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| 2Cl.=>Cl2, 2.CH3=>C2H6, Cl.+.CH3=>CH3Cl |
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| Give two equations for the breakdown of ozone to oxygen catalysed by a chlorine free radical. |
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| Cl. + O3 => ClO. + O2; ClO. + O3 => 2O2 + Cl. |
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| Give two equations for the extraction of copper from malachite (copper(II) carbonate). |
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| CuCO3 => CuO + CO2; 2CuO + C => 2Cu + CO2 |
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| Give two equations for the propagation reactions of the chlorination of methane. |
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| Cl.+CH4=>CH3.+HCl; CH3.+Cl2=>CH3Cl+Cl. |
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| Give two equations to show the reaction of sodium bromide with an excess of sulphuric acid. |
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| NaBr(s)+H2SO4(l) => NaHSO4(s) + HBr(g); 2HBr(g) + H2SO4(l) => SO2(g) + 2H2O(l) + Br2(l) |
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| Give two equations to show the reaction of sodium iodide with concentrated sulphuric acid. |
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| NaI(s) + H2SO4(l) => NaHSO4(s) +HI(g); 8HI(g) + H2SO4(l) => H2S(g) + 4H2O(l) + 4I2(s) |
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| Give two half-equations to show the reaction of hydrogen bromide with sulphuric acid. |
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| 2Br- => Br2 + 2e-; 4H++SO42-+2e-=>SO2 + 2H2O |
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| Give two problems associated with the emission of sulfur oxides. |
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| Acid rain; causes problems for people with asthma. |
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| Give two symbol equations to show the reaction of 1-fluoropropane with a concentrated solution of ammonia in ethanol. |
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| (i) C3H7F + NH3 => C3H7NH3+ + F-; (ii) C3H7NH3+ + F- + NH3 => C3H7NH2 + NH4F |
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| How are sulfide ores converted to oxides, and what is the main environmental problem with this? |
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| Roasting in air; sulfur dioxide produced leads to acid rain |
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| How can the sulfur dioxide produced from roasting sulfide ores be used industrially? |
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| Manufacture of sulfuric acid |
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| How is aluminium recycled? |
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| Collect, melt down, remould |
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| How is copper recycled? Give an ionic equation. |
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| React scrap copper with sulphuric acid to form solutions containing Cu2+ ions, then reduce with scrap iron: Cu2+(aq) + Fe(s) => Cu(s) + Fe2+(aq) |
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| How is the blast furnace heated? |
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| Complete combustion of carbon |
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| How many isomeric alkenes are there with the formula C5H10? Name them all. |
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| 6: pent-1-ene, Z-pent-2-ene, E-pent-2-ene, 2-methylbut-1-ene, 3-methylbut-1-ene, 2-methylbut-2-ene. |
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| If a reaction has a negative enthalpy change, is it exothermic or endothermic? |
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| Exothermic |
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| In the electrolysis of aluminium oxide, why do the anodes need to be constantly replaced? |
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| Elemental oxygen forms at the anode; high temperatures so carbon electrodes burn |
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| In the oxidation of alcohols, what is the oxidising agent and what is the reduction product? |
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| Oxidising agent is acidified orange potassium dichromate(vi) (K2Cr2O7); reduction product is green chromium(iii) ions (Cr3+) |
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| In what medium is aluminium oxide electrolysed, and why? |
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| Molten cryolite; ions must be free to move; cryolite has a lower melting point than aluminium oxide, so lower energy costs |
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| Name and outline a mechanism for the reaction of bromine with propene, and name the product. |
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| Electrophilic addition:=> Curly arrow from double bond to Br with positive partial charge; => Curly arrow from Br-Br bond to Br with negative partial charge; (Intermediates: bromine-containing carbocation and bromide ion); => Curly arrow from lone pair on bromide ion to positive carbon; Product: 1,2-dibromopropane |
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| Name and outline the mechanism for the reaction of a haloalkane with excess ammonia, naming the types of intermediates and the types of products. |
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| => Curly arrow from lone pair on NH3 to ?+ carbon attached to halogen; => Curly arrow from C-X bond to ?- halogen; Intermediates: amino-containing carbocation (with positive charge on one of the hydrogens in the amino group) and halide ion. => Curly arrow from lone pair on NH3 to H+ => Curly arrow from N-H+ bond to N. Products: primary amine and ammonium halide. |
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| Name the catalyst used in the hydration of ethene. |
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| Phosphoric acid |
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| Name the two possible products of the reaction of hydrogen bromide with propene. Which of these will be in greater abundance and why? |
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| 1-bromopropane, 2-bromopropane. 2-bromopropane is preferential because secondary carbocation intermediate is more stable than primary carbocation intermediate (due to positive inductive effect). |
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| Name two types of plastic recycling. |
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| Mechanical and feedstock recycling |
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| Of chloride, bromide and iodide, which has the greatest reducing ability and why? |
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| Iodide; outer electron further from nucleus with more shielding, so more easily lost |
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| On the mass spectrum of a molecule, which peak represents the molecular ion? |
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| The furthest significant peak to the right; the tiny peak just to the right of it is due to isotopes. |
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| Other than safety, state why very high pressures are not used in the Haber process. |
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| Less electrical pumping cost and less expensive equipment (e.g. piping) |
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| Outline the mechanism for a nucleophilic substitution reaction of a haloalkane where the nucleophile is an anion, and name the types of products. |
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| => Curly arrow from lone pair on nucleophile to ?+ carbon attached to halogen; => Curly arrow from C-X bond to ?- halogen. Products: alcohol or nitrile, metal halide |
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| Outline the mechanism for an elimination reaction and state the types of products. |
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| => Curly arrow from lone pair on OH- ion to ?+ hydrogen atom adjacent to halogen; => Curly arrow from C-H bond to C-C bond; => Curly arrow from C-X bond to ?-negative halogen. Products: alkene, water and metal halide. |
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| State a use of barium sulphate. |
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| Used in barium meal to outline the gut in medical X-rays |
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| State a use of calcium hydroxide. |
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| Used in agriculture to neutralize soils. |
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| State a use of ethene. |
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| Making plastics/used to make polyethene |
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| State a use of magnesium hydroxide. |
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| Milk of magnesia for curing indigestion and acid reflux |
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| State and explain the effect of an increase in pressure on the yield of ammonia in the Haber process. |
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| Yield increases; there are fewer moles on the right hand side (products); the equilibrium shifts to the right to oppose the increase in pressure |
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| State and explain the effect of an increase in temperature on the yield of ammonia in the Haber process. |
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| Yield decreases; the forward reaction is exothermic; equilibrium shifts to the left to oppose the increase in temperature/lower the temperature. (When answering equilibria questions which are three marks, these are always your three marking points. You must be specific about the change which is opposed.) |
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| State four essential conditions for fermentation. |
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| Anaerobic; aqueous; yeast/zymase; 37oC/body temperature |
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| State Hess' Law. |
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| The enthalpy change of a reaction is independent of the route taken. |
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| State the meaning of the term "carbon neutral". |
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| No net carbon (dioxide) emissions to atmosphere |
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| State the meaning of the term "hydration". |
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| The addition of water to a molecule/compound. |
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| State the meaning of the term stereoisomers. |
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| Compounds with the same structural formula, but whose atoms are arranged differently in space. |
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| State two uses of chlorine and explain why it is used for these purposes. |
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| Swimming pools and purification of drinking water; it reacts with water to form chloric(I) acid which kills bacteria by oxidation |
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| Suggest arguments in favour of the production of ethanol by hydration of ethene over fermentation of glucose. |
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| =; Pure ethene produced - doesn't need to be distilled (so economically better); => Continuous process rather than batch process - can carry on going - also increases profit; => 100% atom economy/ethanol is the only product (fermentation produces CO2); => Fermentation of glucose has ethical issues as sugar cane is grown in poor countries where the land is needed for food. |
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| Suggest arguments in favour of the production of ethanol by fermentation of glucose over hydration of ethene. |
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| => Renewable source of glucose (so better for environment); => Carbon-neutral (so better for environment); => Lower temperatures needed as enzymes operate best at 37o (so fewer energy costs); => Does not require cracking of crude oil, which is expensive as it has high energy costs. |
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| Suggest three factors affecting which method is used for metal extraction. |
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| Energy requirements (heat, electricity); cost of reducing agents; purity required |
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| Suggest why it is not possible to measure the enthalpy change directly for the following reaction: C(s,graphite) + 1/2O2(g)=>CO(g) |
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| Carbon monoxide is not the only product as some complete combustion occurs. |
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| What are the conditions needed to make high density polythene? |
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| Temperature&pressure just above rtp; Ziegler-Natta catalyst |
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| What are the conditions needed to make low-density polythene, and what is the name of the mechanism? |
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| High temperature&pressure; free radical mechanism |
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| What are the electrodes made of in the electrolysis of aluminium oxide? |
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| Graphite |
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| What are the features of the Maxwell-Boltzmann curve? |
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| Starts at origin; skewed to the left; gets less steep over time on the left; gets less steep over time on the right and asymptotic to x-axis. (An examiner will insist on the initial part of the curve getting less steep over time.) |
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| What are the three isomeric products of the dehydration of butan-2-ol? |
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| But-1-ene; E-but-2-ene; Z-but-2-ene |
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| What are the three stages of the pathway of the chlorination of methane? |
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| Initiation reactions, propagation reactions and termination reactions |
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| What are the useful properties and uses of titanium? |
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| Abundant, low density and corrosion resistant; strong alloys for aircraft, prosthetic limbs |
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| What are the uses of long chain CFCs? |
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| Dry cleaning and de-greasing solvents |
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| What are the uses of short chain CFCs? |
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| Aerosol propellants and refrigerants |
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| What conditions are used in the industrial hydration of ethene and why? |
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| 570K (compromise between yield and ROR); 6500kPa (compromise between yield and cost/ethene polymerising) |
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| What does CFC stand for? |
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| Chlorofluorocarbon |
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| What environmental problems are associated with the destruction of the ozone layer? |
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| Ozone protects from UV light; overexposure to UV would be harmful to plankton, the lowest organisms in the food chain in the ocean, disrupting whole ecosystems; and UV could cause skin cancer. |
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| What environmental problems are associated with the extraction of iron? |
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| Carbon dioxide (greenhouse gas) and carbon monoxide (poisonous) produced in the blast furnace; sulfur dioxide produced by roasting sulfide ores |
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| What happens to the Maxwell-Boltzmann distribution when temperature is increased? |
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| Peak shifts to the right and is lower; many more molecules have E>Ea |
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| What is a free radical? |
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| An atom or molecule with an unpaired electron |
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| What is a nucleophile? |
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| Negative ion or atom with a partial negative charge which has a lone pair that attacks areas of electron deficiency. |
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| What is a reducing agent? |
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| A species that donates electrons in a redox reaction |
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| What is an ore? |
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| A rock containing enough metal for extraction to be profitable |
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| What is an oxidizing agent? |
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| A species that gains electrons in a redox reaction |
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| What is disproportionation? Give an example of a redox reaction in which disproportionation takes place. |
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| A redox reaction where some atoms of an element are oxidised and some atoms of the same element are reduced. Examples: the reaction of chlorine with water to form chloric(I) acid and hydrochloric acid; the reaction of chlorine with sodium hydroxide to form sodium chlorate, sodium chloride and water. |
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| What is photodissociation? |
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| When a chemical bond is broken by light energy |
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| What is the charge on a barium ion? |
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| 2+ |
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| What is the charge on a calcium ion? |
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| 2+ |
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| What is the charge on a carbonate ion? |
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| 2- |
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| What is the charge on a hydrogen ion? |
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| 1+ |
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| What is the charge on a hydroxide ion? |
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| 1- |
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| What is the charge on a lead ion? |
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| 2+ |
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| What is the charge on a lithium ion? |
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| 1+ |
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| What is the charge on a magnesium ion? |
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| 2+ |
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| What is the charge on a nitrate ion? |
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| 1- |
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| What is the charge on a potassium ion? |
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| 1+ |
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| What is the charge on a silver ion? |
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| 1+ |
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| What is the charge on a sodium ion? |
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| 1+ |
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| What is the charge on a sulphate ion? |
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| 2- |
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| What is the charge on a sulphide ion? |
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| 2- |
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| What is the charge on a zinc ion? |
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| 2+ |
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| What is the charge on an aluminium ion? |
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| 3+ |
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| What is the charge on an ammonium ion? |
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| 1+ |
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| What is the charge on an oxide ion? |
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| 2- |
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| What is the main cost of electrolysis? What is a solution to this? |
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| Cost of generating electric current; plants built near HEP stations |
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| What is the name of the enzyme which carries out fermentation? |
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| Zymase |
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| What is the name of the main aluminium-containing ore? |
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| Bauxite |
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| What is the name of the main iron-containing ore? |
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| Haematite |
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| What is the name of the main titanium-containing ore? |
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| Rutile |
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| What is the organic product of an elimination reaction? |
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| An alkene |
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| What is the oxidation product of a reaction of an aldehyde with Tollens' reagent? |
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| Carboxylic acid |
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| What is the reduction product of the reaction of an aldehyde with Fehling's reagent? |
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| Copper(I) oxide/ copper(I)ions |
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| What is the reduction product of the reaction of an aldehyde with Tollens' reagent? |
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| Silver |
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| What is the role of the hydroxide ion in an elimination reaction? |
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| A base |
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| What is the role of the hydroxide ion in nucleophilic substitution? |
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| A nucleophile |
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| What is the standard enthalpy of formation of oxygen? |
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| 0 (as for all elements) |
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| What is the trend in the solubility of the hydroxides going down group II from magnesium to radium? |
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| Increases |
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| What is the trend in the solubility of the sulfates going down group II from magnesium to radium? |
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| Decreases |
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| What name is given to a geometric isomer which has similar chemical groups on the same side of the C=C bond? |
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| Z-isomer |
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| What type of reaction is the chlorination of methane? |
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| Free-radical substitution reaction |
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| What type of reaction is the dehydration of an alcohol? |
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| Elimination |
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| When sodium halides react with excess sulphuric acid, what state are the sodium halides in? |
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| Solid |
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| When sulfides are roasted, sulfur dioxide is produced. If this enters the atmosphere it will dissolve in rainwater to form sulfuric acid (acid rain). How do manufacturers prevent this from happening? |
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| Sulfur dioxide is collected to stop it from entering the atmosphere, and is then used to make sulfuric acid. |
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| Which of 1-fluorobutane and 1-iodobutane is more reactive and why? |
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| 1-iodobutane; C-I bond has a lower bond enthalpy than C-F so is more easily broken; this is a more important factor than the greater polarity of the C-F bond. |
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| Which of but-1-ene and but-2-ene exhibits geometric isomerism? Explain why the other does not. |
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| But-2-ene. In but-1-ene, the first carbon is attached to two hydrogen atoms. |
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| Which of substitution and elimination is favoured at high temperatures? |
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| Elimination |
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| Which of substitution and elimination is favoured by primary haloalkanes? |
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| Substitution |
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| Which of substitution and elimination is favoured by tertiary haloalkanes? |
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| Elimination |
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| Which of substitution and elimination is favoured in aqueous conditions? |
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| Substitution |
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| Which of substitution and elimination is favoured in ethanol? |
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| Elimination |
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| Why are iodide ions stronger reducing agents than chloride ions? |
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| In iodide ions, the outer electrons are further from the nucleus with more electron shielding than in chloride ions, so the attraction of the outer electrons to the nucleus is weaker. |
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| Why are tertiary alcohols not easily oxidised? |
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| The carbon with the functional group has no hydrogen atoms attached, and C-C bonds are much harder to break than C-H bonds. |
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| Why do ketones not react with Tollens', Fehling's or Benedict's reagents? |
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| Ketones are not reducing agents/functional carbon has no hydrogen atoms attached |
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| Why does methylbut-2-ene not exhibit geometric isomerism? |
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| One of the double bond carbons has two methyl groups attached |
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| Why have politicians agreed to put restrictions on the use of CFCs? |
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| In the atmosphere, they are broken down by UV light to free radicals and break down the ozone layer |
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| Why is carbon reduction not used for the extraction of titanium, tungsten and aluminium from their ores? |
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| The metals react with carbon to form carbides |
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| Why is limestone added to the blast furnace? |
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| To remove silicon dioxide impurities from the ore; they react to form calcium silicate (slag) which is removed from the bottom of the blast furnace |
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| Why is titanium not extracted by electrolysis? |
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| Titanium has to be very pure to have low density and be corrosion resistant; electrolysis does not make sufficiently pure titanium to have these properties. |
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| Write an equation for the conversion of sulfur dioxide into sulfuric acid used in industry. |
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| 2SO2 + 2H2O + O2 => 2H2SO4 |
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| Write an equation for the roasting of zinc sulfide in air. |
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| 2ZnS + 3O2 => 2ZnO + 2SO2 |
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| Write equations for the four main redox reactions in the blast furnace. |
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| (i) C + O2 => CO2 (ii) C + CO2 => 2CO (iii) Fe2O3 + 3CO => 2Fe + 3CO2 (iv) Fe2O3 + 3C => 2Fe + 3CO |
