Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
61 Cards in this Set
- Front
- Back
|
Give two features of a reaction at equilibrium. (2 marks) |
M1 Concentration(s) (of reactants and products) remain or stayconstant / the same M2 Forward rate = reverse / backward rate |
|
|
Bromine is one of the products formed when concentrated sulfuric acid reacts with hydrogen bromide. Write an equation for this reaction. State the role of sulfuric acid in this reaction. (3 marks) |
M1 SO2 identified M2 correctly balanced equation (would also gain M1)2HBr + H2SO4 --> Br2 + SO2 + 2H2O Mark M3 independently: Oxidising agent OR electron acceptor OR oxidantOR to oxidise the bromide (ion) / HBr |
|
|
The following pair of compounds can be distinguished by a simple test-tube reaction. For the pair, give a suitable reagent that could be added separated to each compound to distinguish between them. Describe what you would observe. HCl and HNO3 (3 marks) |
M1 AgNO3 OR silver nitrate OR any soluble silver salt M2 white precipitate or white solid / white suspension M3 remains colourless OR no reaction OR no (observed) changeOR no precipitate |
|
|
Ethanol is an important industrial compound. Ethanol can be produced by the hydration of ethene. The equation for the equilibrium that is established is: C2H4 + H20 --> CH3CH2OH The operating conditions for the process are a temperature of 300 degrees and a pressure of 7 MPa. Under these conditions, the conversion of ethene into ethanol is 5%. Identify the catalyst used in this process. Deduce how an overall yield of 95% is achieved in this process without changing the operating conditions. (2 marks) |
M1 c(oncentrated) phosphoric acid / c(onc.) H3PO4 OR c(oncentrated) sulfuric acid / c(onc.) H2SO4 M2 Re-circulate / re-cycle the (unreacted) ethene (and steam) / the reactants OR pass the gases over the catalyst several / many times |
|
|
Explain how you could distinguish between a racemic mixture (racemate) of lactic acid and one of the enantiomers of lactic acid. (2 marks) |
M1 (Plane) polarized light M2 (Polarised light) rotated by single enantiomer but unaffected by racemate |
|
|
Suggest an alternative name for the term acidity regulator. Explain how a mixture of lactic acid and sodium lactate can act as a regulator when natural processes increase the acidity in some foods. (3 marks) |
M1 buffer M2 Large lactate concentration in buffer OR sodium lactate completely ionised M3 added acid reacts with/is removed by lactate ion or A– or sodium lactate or salt M4 ratio [HA]/[A-] stays almost constant |
|
|
Suggest why the reaction of ammonia with benzene might be considered unexpected. (2 marks) |
M1 ammonia is the nucleophile M2 benzene repels nucleophiles |
|
|
The dipeptide of lysine and alanine is hydrolysed in acid conditions and the mixture produced is analysed by column chromatography. The column is packed with a resin which acts as a polar stationary phase. Suggest why lysine leaves the column after alanine. (2 marks) |
M1 In acid lysine has double positive or more positive charge M2 (Lysine ion) has greater affinity / greater attraction / adheres better / sticks better to polar / stationary phase |
|
|
In terms of the forces acting on particles, suggest one reason why the first electron affinity of oxygen is an exothermic process. (1 mark) |
There is an attractive force between the nucleus of an O atom andan external electron. (Allow any statement that implies attraction between thenucleus and an electron) |
|
|
The standard free-energy change for the formation of magnesium oxide from magnesium and oxygen, -570kJmol-1. Suggest one reason why a sample of magnesium appears to be stable in air at room temperature, despite this negative value. (1 mark) |
Forms a protective layer/barrier of MgO / MgO prevents oxygenattacking Mg OR Allow activation energy is (very) high OR Allow reaction (very) slow |
|
|
The reaction is zero order with respect to B. State the significance of this zero order for the mechanism of the reaction. (1 mark) |
Slow step or rds involves only A OR B does not appear in the slow step or the rds OR B only appears after the slow step or the rds |
|
|
State the effect, if any, of using a smaller flask on the value of Kc. (1 mark) |
insoluble |
|
|
Suggest one property of the aluminium oxide coating that causes aluminium to resist corrosion in water. (1 mark) |
M1: [H2O] is very high (compared with [H+] and [OH–]) OR Very few H+ and OH– ions OR Only / very slightly dissociates OR M2: Equilibrium lies far to the left[H2O] is (effectively) constant OR is incorporated into the constant K |
|
|
Explain why the value of Kw increases as the temperature increases. (2 marks)
|
M1 (Dissociation OR breaking bonds) is endothermic M2 ∴ Equilibrium moves to RHS (at higher T) to absorb heat or tolower T or oppose increase in T |
|
i. Use the enthalpy of hydrogenation of a double bond (-120kJmol-1) to calculate a value for the enthalpy of hydrogenation of cyclohexa-1,4-diene. (1 mark) ii. Predict a value for the enthalpy of hydrogenation of cyclohexa-1,3-diene. (1 mark) iii. Explain your answers to the question above in terms of the bonding in these two dienes. (3 marks) |
i. -240 (kJ mol-1) ii. between -239 and -121 (kJ mol-1) iii. M1 Proximity – for 1,3 C=C bonds are close together M2 Delocalisation – for 1,3 some delocalisation ORsome overlap of electrons, π clouds or p orbitals M3 some extra stability for the 1,3- isomer |
|
|
Phosphorus(V) oxide is known as phosphorous pentoxide. Suggest why it is usually represented by P4O10 rather than by P2O5? (1 mark) |
One molecule contains 4P and 10O OR the molecular formula is P4O10 OR exists as P4O10 |
|
|
State the type of bonding in magnesium oxide. Outline a simple experiment to demonstrate that magnesium oxide has this type of bonding. (3 marks) |
M1 Ionic bonding M2 Melt it M3 conducts electricity |
|
Hydrogen is used to convert oleic acid into stearic acid as shown by the following equation. Use your knowledge of the chemistry of alkenes to deduce the type of reaction that has occurred in this conversion. (1 mark) |
Addition OR (catalytic) hydrogenation OR Reduction |
|
|
State the meaning of the term enthalpy change. (1 mark) |
Heat energy change at a constant pressure |
|
|
The excess of magnesium used in this extraction can be removed by reacting it with dilute sulfuric acid to form magnesium sulfate. Use your knowledge of Group 2 sulfates to explain why the magnesium sulfate formed is easy to separate from the titanium. (1 mark) |
It or MgSO4 is soluble OR forms a solution (and is washed away) OR dissolves |
|
|
State the type of structural isomerism shown by propanal and propanone. (1 mark) |
functional group |
|
|
The infrared spectrum of an isomeric alcohol is given. Identify one feature of the infrared spectrum which supports the fact this is an alcohol. Explain how infrared spectroscopy can be used to identify this isomeric alcohol. (3 marks) |
M1 The infrared spectrum shows an absorption / peak in the range 3230 to 3550 (cm-1)(which supports the idea that an alcohol is present) M2 Reference to the ‘fingerprint region’ or below 1500 (cm-1) M3 Match with or same as known sample / database spectra |
|
|
Write an equation for the complete combustion of butan-1-ol and state why it can be described as a biofuel. (1 mark) |
A biofuel is a fuel produced from (renewable) biological (re)source(s) OR (renewable) (re)source(s) from (a specified) plant(s) /fruit(s) /tree(s) |
|
|
Explain why the boiling points increase H2S to H2Te. (2 marks) |
M1 Atoms/molecules get larger/more shells/more electrons/ more surface area M2 therefore increased Van der Waals/IMF forces |
|
Some students were asked to suggest methods distinguish between isomers Q and R. One student suggested testing the optical activity of the products formed from Q and R were reacted separately with HCN. By considering the optical activity of these products formed from Q and R, explain why this method would not distinguish between Q and R. (3 marks) |
M1 Product from Q is a racemic mixture/ equal amounts of enantiomers M2 racemic mixture is inactive or inactive explained M3 Product from R is inactive (molecule) or has no chiral centre |
|
|
Give a use for a mixture of methyl esters formed by reacting a triester with methanol. (1 mark) |
biodiesel |
|
|
Suggest one reason why poisoning reduces the effectiveness of a heterogeneous catalyst. (1 mark) |
blocks active site |
|
|
Suggest how poisoning of a catalyst, used in an industrial process, can be minimised. (1 mark) |
remove impurities |
|
|
Other than it's lack of pollution, state briefly the main advantage of a fuel cell over a rechargeable cell such as the nickel-cadmium cell when used to provide power for an electric motor that propels a vehicle. (1 mark) |
hydrogen and oxygen are supplied continuously |
|
|
Explain the meaning of the term perfect ionic model. (1 mark) |
Ions can be regarded as point charges (or perfect spheres) |
|
|
State whether you would expect the value of the theoretical enthalpy of lattice dissociation for silver chloride to be greater than, equal to or less than that for silver bromide. Explain your answer. (3 marks) |
Greater Chloride ions are smaller than bromide They are attracted more strongly to the silver ions |
|
|
State and explain one risk associated with the use of cisplatin as an anticancer drug. Risk: Explanation: (2 marks) |
kill cells may attach to any DNA |
|
|
State the electron configuration of a Ti (III) ion and that of a Ti(IV) ion. Explain, in terms of electron configurations and electron transitions, why Ti(III) compounds are usually coloured but Ti(IV) compounds are colourless. (5 marks) |
1s2 2s2 2p6 3s2 3p6 1s2 2s2 2p6 3s2 3p6 3d1 Ti(III) has a d electron that can be excited to a higher level Absorbs one colour of light from white light Ti(IV) has no d electron so no electron transition with energy equalto that of visible light |
|
|
Give two reasons why the use of a spectrometer is the most appropriate method for measuring the concentration of the coloured ions in this experiment. (2 marks) |
M1 Rapid determination of concentration M2 Does not use up any of the reagent/does not interfere with the reaction |
|
|
At room temperature, 2-aminobutanoic acid exists as a solid. Draw the structure of the species present in the solid form. (1 mark) |
|
|
|
The amino acid, glutamic acid show to the side. Draw the structure of the organic species formed when glutamic acid reacts with an excess of methanol in the presence of concentrated sulfuric acid. (1 mark) |
It forms esters. |
|
|
A tripeptide was heated with hydrochloric acid and a mixture of amino acids was formed. This mixture was separated by column chromatography. Outline briefly why chromatography is able to separate a mixture of compounds. (3 marks) |
M1 phase or eluent or solvent (or named solvent) is moving ormobile M2 stationary phase or solid or alumina/silica/resin M3 separation depends on balance between solubility or affinity(of compounds) in each phase OR different adsorption or retention OR(amino acids have) different Rf values OR(amino acids) travel at different speeds or take different times |
|
|
At temperatures below around 3000K, the decomposition of NO into its elements should be spontaneous. However, in car exhausts, this decomposition reaction does not take place in the absence of a catalyst. Suggest why this spontaneous decomposition does not take place. (1 mark) |
Activation energy is high |
|
|
In a mass spectrometer, under the same conditions, N-14 and N-15 single positive ions follow different paths. State one change in the operation of the mass spectrometer that will change the path of an ion. (1 mark) |
Electromagnet/ electric field/ magnet /acceleratingpotential or voltage / electric current |
|
|
State which has the larger radius, a sodium atom or a sodium ion (Na+). Explain your answer. (2 marks) |
Na/sodium (atom) (larger than Na+/sodium ion) (1) Ion has one less shell/energy level than atom (1) [accept correct references to 2p and 3s sub-levels] [Not ‘less electrons, so more attraction’] |
|
|
Suggest why a chloride ion (Cl-) has a larger radius than a chlorine atom. (2 marks) |
1s22s22p63s23p5 → 1s22s22p63s23p6 / ion has more electrons/fills its outershell (1) Ion has more e-- e- repulsion (1) |
|
|
Two different chlorine-containing compounds are formed when chlorine reacts with cold, dilute sodium hydroxide solution. One of these compounds is sodium chloride. Name the other chlorine containing compound formed. (1 mark) |
sodium chlorate |
|
|
State three essential conditions for the fermentation of aqueous glucose in Process 2. (3 marks) |
M1 Anaerobic conditions M2 temperature 37-42 M3 yeast |
|
|
Give one reason, other than heat lost, why the value obtained from a student's calorimetry experiment results is less exothermic than a data book value. (1 mark) |
Incomplete reaction |
|
|
Describe the structure of and bonding in graphite and explain why the melting point of graphite is very high. (4 marks) |
1 Layers of (C atoms) 2 Connected by covalent bonds within each layer 3 Van der Waals forces/ IMF between layers/ weak forcesbetween layers 4 Many/strong covalent bonds need to be broken |
|
3 marks |
|
|
|
State the type of bonding in sodium oxide. Explain why sodium oxide reacts to form an alkaline solution when added to water. (3 marks) |
1 ionic 2 O2– / oxide ion reacts with water / accepts a proton 3 forming OH– ions/ NaOH / sodium hydroxide (can show in equation from Na2O even if incorrect) |
|
|
Describe what you would observe when sulfur burns in oxygen. Write n equation for the reaction that occurs. State the type of bonding in the oxide formed. (4 marks) |
1 blue flame 2 fumes or misty or pungent/choking/smelly gas 3 S + O2 --> SO2 4 covalent |
|
|
Write an ionic equation to show how aluminium oxide reacts with aqueous sodium hydroxide. (1 mark) |
Al2O3 + 2OH–+3H2O --> 2Al(OH)4– or Al2O3 + 6OH–+3H2O --> 2Al(OH)63– |
|
|
Explain why the voltage remains constant in a feul cell. (2 marks) |
1 reagents / fuel supplied continuously 2 concentrations (of reagents) remain constant |
|
|
Explain, with the aid of an equation, why iron (III) ions are more acidic than iron (III) ions in aqueous solution. (3 marks) |
1 [Fe(H2O)6] 3+ --> [Fe(H2O)5OH]2+ + H+ 2 Fe3+ ion has higher charge (to size ratio) (than Fe2+) 3 increases polarisation of co-ordinated water / attracts O releasing an H+ ion / weakens O—H bond |
|
|
State how, if at all, the number of molecules with the most probable energy changes as the temperature is decreased without changing the total number of molecules. (1 mark) |
increase |
|
|
Name the catalyst involved in the hydration of but-2-ene. (1 mark) |
sulfuric acid |
|
|
Suggest one property of the aluminium oxide coating that causes aluminium to resist corrosion in water. (1 mark) |
insoluble |
|
|
Explain why the enthalpy of atomisation of chlorine is exactly half the bond dissociation enthalpy of chlorine. (1 mark) |
only one mole of atoms are formed, not two moles |
|
|
Suggest why a value for the enthalpy of solution of magnesium oxide is not found in any data books. (1 mark) |
it forms magnesium hydroxide it is not soluble |
|
|
Sulfur dioxide reacts with water to form a weakly acidic solution. Ions are formed when sulfur dioxide reacts with water. Write an equation for this reaction. (1 mark) With reference to your equation from above, suggest why sulfur dioxide forms a weakly acidic solution. (1 mark) |
M1 H20 + SO2 <--> HSO3- + H+ M2 reaction doesn't reach equilibrium, partial dissociation |
|
|
Consider the reaction when an excess of dilute sulfuric acid is added to a solution containing CrO4 2- ions. What is the colour of the original solution? What is the observation after an excess of reagent has been added? (3 marks) What is the equation? |
M1 Yellow M2 Orange solution M3 8H+ + 3e- + CrO4 2- --> Cr3+ + 4H2O |
|
|
Give one reason why impurities in the reactants can cause problems in processes that use heterogeneous catalysts. (1 mark) |
Absorbs on the catalyst so decreases the surface are contact with the catalyst |
|
|
Suggest one reason why the value for the enthalpy change of anhydrous copper (II) sulfate to hydrated copper (II) sulfate cannot be measured directly. (1 mark) |
solution is quick to form cannot measure the temperature change of solids |
|
|
The freezing of water is an exothermic process. Give one reason why the temperature of a sample of water can stay at a constant value of 0 degrees when it freezes. (1 mark) |
heat given out escapes |
