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65 Cards in this Set
- Front
- Back
Explain why chloroethanoic acid is a stronger acid than ethanoic acid? 2 |
Electronegative chlorine withdraws electrons. This stabilises the charge on COO- so chloroethanoic acid with dissociates more readily |
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Explain why Ka values do not usually contain called for Ka for strong acids |
Strong acid fully dissociate So Ka values would tend to infinity |
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Suggest why initial rates are used rather than other rates to determine orders |
At t=0 the concentrations are known |
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State how to work out initial rate from a graph |
Gradient of tangent At t=0 |
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Explain why the the enthalpy for lattice dissociation potassium oxide is less endothermic than that of sodium oxide |
K ion is bigger than Na ion Attraction between oppositely charged ions weaker |
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Write equations for the Hydrogen oxygen fuel cell |
Positive electrode: O2 + 2H2O+4e-→4OH- Negative electrode: H2 + 2OH- → 2H2O +2e- Overall : 2H2 + O2 → 2H2O |
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Show on a diagram how the emf of a Hydrogen oxygen fuel cell changes with time |
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State the main environmental advantage of the Hydrogen oxygen fuel cell |
Water is the only product No pollutants |
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Write equations to show vanadium V oxide as a catalyst in the contract process |
SO2+V2O5 → SO3 + V2O4 V2O4+ 1/2O2→ v2O5 |
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Describe how ions are detected on mass spec |
Ions hit the detector and accept an electron This generates a current |
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State and explain one similarity and one difference between spectra from an electron with higher energy |
Similarity Some peaks at same m/z values As same sample is being ionised and detected Difference Has extra peak at 1/2 m/z values As knocked off two electrons |
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Explain how VDWs forces arise |
the movement of electrons in the first molecule causes a temporary dipole This induces a dipole in the second molecule Causes an attraction between neighbouring molecules |
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State the mz value of the ion that produces the biggest current and explain your answer |
128 most abundant ion |
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Predict whether the atomic radius of 124 Te compared to 125Te |
Same same no of protons and electrons |
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Suggest how a student can check all the water has been removed |
Heat To a constant mass |
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Identify which isotope is deflected the most in the magnetic field, explain why |
70 lowest mz |
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Explain why a decrease in temp decreases the rate |
Fewer particles have enough sufficient energy to react Less successful collisions in given time |
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Give two features of a reaction at equilibrium |
Concentrations remain constant Forward rate = reverse rate |
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Suggest why using powders increases rate |
increases successful collisions in given time to increase the surface contact between particles |
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with ref to IMFs explain why we can extract aldehydes with distillation but not coohs |
COOHs form hydrogen bonds which are stronger than IMFs in aldehydes |
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Explain how a mixture of lactic acid and sodium lactate can act as a buffer 3 |
large lactate conc in buffer reacts with base HA --> H+ + A- added acid reacts with lactate ions ratio ha/ a- stays almost constant |
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Explain why the enthalpy of hydration for Cl- more negative than for Br- (3) |
chloride ion is smaller than bromide ion- higher CD so force of attraction between chloride ions and water stronger chloride ions attract the d+ of water |
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Explain why entropy is zero when temp is zero |
Particles are stationary No disorder |
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Suggest why silicon dioxide is insoluble in water |
Macromolecular Covalent bonding water cannot break the covalent bonds |
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Explain why after some time the current falls to zero |
the Cu2+ in each electrode will be at the same conc |
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Write the equations for the lithium ion cobalt cell |
Li+ + CoO2 + e- --> Li+[CoO2]- Li----> Li+ + e- Overall Li + CoO2 ---> Li[CoO2]
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Explain why transition metal causes a solution to be coloured [2] |
Light is absorbed to excite an electron Some wavelengths are absorbed as electrons jump to higher orbitals The remaining colour wavelength is transmitted |
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Deduce why the bonding in NO2 is covalent rather than ionic |
small difference in electronegativity |
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Explain why initially the reaction between C2O42- and mno4- ions is initially very slow. [3] |
2 negative ions repel Not many Mn2+ present initially to catalyse the reaction The activation energy is too high |
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Describe how colorimetry can determine the conc of sol [3] |
measure absorbance against solutions of known varying concentrations Plot Graph absorbance against conc Read off unknown conc from calibration curve |
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Describe the steps you would take to determine the accurate temp of (delta H) that is not influenced by the surroundings [4] |
measure temp of water - colorimetry add powder and stir once start clock measure temp every minute after adding solid for 5 mins plot temp against time. plot line of best fit and extrapolate to time of mixing and determine temp change |
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Explain why there are differences in hydration enthalpies of the Mg2+ and Na+ |
Mg2+ is smaller and more highly charged than sodium ion magnesium ion attracts water more strongly |
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Define electron affinity for chlorine |
the enthalpy change when one mol of chlorine atoms forms one mol chloride 1- ions all atoms and ions in gaseous states |
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Define mean bond enthalpy |
the enthalpy to one mole of a H-O bonds averaged over a range of compounds |
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Suggest why the electron affinity for flourine has a negative value |
there is an attraction between the nucleus and electron energy is released |
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Explain why the theoretical enthalpy of lattice dissociation for AgF is different from its experimental value |
AgF isnt perfectly ionic/ has some covalent character theoretical lattice enthalpy assumes only ionic interaction |
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State structure, bonding and physical properties of SiO2 |
Macromolecular covalent bonding hard, brittle insoluble doesn't conduct electricity |
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suggest why hydration of an ion is exothermic |
water is polar cl- attracts h in water |
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use half equations to show how an electrical current is generated |
hydrogen electrode produces electrons oxygen electrode accepts electrons |
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Describe how to prepare a standard solution |
weigh a weighing boat containing solid on a 2dp balance transfer to beaker and reweigh weighing boat record difference in mass add deionised water stir until all solid has dissolved transfer to volumetric flask with washings make 250 cm3 mark with water invert |
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Explain why the complexes are different colours |
in each of P and the oxidation state of Cr is +3 the electron configuration is the same\ ligands are different different energies of d electrons different wavelengths of light are absorbed, different wavelengths of light are transmitted |
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Explain thermodynamically why this reaction occurs- chelate effect |
4 particles becomes 7 entropy increases delta h is approx zero delta g is negative |
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suggest how the risk associated with cisplatin can be minimised |
use in small amounts |
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suggest two properties of ions that influence the value of lattice enthalpy |
ionic radius ionic chage density |
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why does entropy increase as particles gain kinetic energy |
as temp increases particles vibrate disorder increases |
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Outline an experiment to demonstrate that MgO has ionic bonding |
Melt it molten oxide conducts electricity |
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why is SiO2 insoluble |
macromolecular covalent water cannot break the covalent bonds/ enthalpy of hydration is less than bond enthalpy |
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State different features that cause a change in the value for delta E [3] |
metal ligand shape oxidation state coordination number |
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What is the effect of the addition of a catalyst on rate [3] |
increases rate lowers activation energy by providing an alternative route allows more molecules able to react |
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Justify the use of a compromise temp |
High temp gives a low yield but low temp gives a low rate so compromise |
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Suggest how metals can be extracted from their sulfide ore. expain how pollution problems arise |
extract from metal oxide pollution sulfur dioxide causes acid rain |
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explain in terms of electronegativity why the boiling point of H2S2 is lower than H2O2 |
S is less electronegative than O. no hydrogen bonds |
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Name the type of cracking that produces a high percentage of alkenes |
thermal high temps and pressure |
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Describe how you would measure the melting point of aspirin [2] |
Place sample of aspirin into capillary tube heat in melting point apparatus slowly near melting point |
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Compare the production of ester from acylcchloride and alcohol vs carboxylic acid and alcohol |
1 Faster bigger yield purer product Disadvantage HCl toxic fumes |
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Outline briefly why column chromatography is able to separate a mixture [3] |
the solvent is moving the aumina beads remain stationary separation as different compounds have different balance between retention to the stationary phase and different solubility in the moving phase |
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Suggest why the databook enthalpy is different to experimental enthalpy [2] |
heat loss or absorbed by apparatus incomplete combustion may not be in standard states MBE vary with different compounds |
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Outline the method of recrystallisation |
Dissolve in MINimum volume of hot solvent filter hot allow to cool filter dry residue under suction |
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with reference to electrons, explain why aqueous copper 2 ions are blue |
absorbs certain frequencies of light\ d electrons excited the colour observed is the light transmitted |
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State the meaning of each of the 3 terms in DE=hv |
Delta E = is the energy gained by the excited electrons h=plancks constant v= frequency of light absorbed by Cu2+ |
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explain why the shape of CuCl4 differs from the hexaaqua copper ion |
Cl- too big- to fit more than 4 round Cu |
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Explain how and why iron ions catalyse the reaction between iodide ions and S2O8 2- ions . write equations [5] |
2Fe2+ +S2O8 2- ---> 2SO4 2- +2Fe3+ 2Fe3+ + 2I- ---> I2 + 2Fe2+ How: as iron ions have variable oxidation states and provide a route with a lower activation energy why: two negative ions repel |
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Describe how electron impact ionisation is done 4 |
High energy electrons From electron gun Fired at sample Knocks off one electron |
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Describe how electrospray ionisation is done (4) |
Sample dissolved in volatile solvent Injected through a hypodermic needle giving a fine mist Tip of needle has high voltage Each gains a proton as it leaves the needle |
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Explain why Fe h20 and Fe cl4 are different shaped |
Cl- is a bigger ligand Can only for 4 around |