General revision
No description yet. This curated deck is ready for daily study.
Card preview (24)
What gives a violet colour if shaken with organic solvent
Iodine
What are the conditions when chlorine reacts with sodium hydroxide to form bleach
Cold and dilute
The reactivity of group 2 elements increases down the group, explain why (3 marks)
Increasing size: Atomic radius increases OR more shells OR more (electron) shielding Attraction Nuclear attraction decreases OR (outer) electron(s) experience less attraction Ionisation energy Ionisation energy decreases OR less energy needed to remove electron(s)
State 2 sources of nitrogen oxides in the stratosphere
• Lightning/ thunderstorms • Aircrafts
What type of reaction has the greatest atom economy - Substitution - Hydrolysis - Elimination - Addition
Addition
Define stereoisomer
Same structural formula and different arrangement of atoms in space
Suggest whether the enthalpy change of vapourisation of bromine is exothermic or endothermic. Explain your answer
Endothermic, Energy required to overcome induced dipole–dipole forces/London forces
Explain in terms of bonds breaking and bond forming, why a reaction can be exothermic
More energy is released by forming bonds than energy required when breaking bonds
Define the standard enthalpy change of combustion (3 marks)
-(enthalpy change that occurs) when one mole of a substance - completely combusts OR reacts fully with oxygen - 298 K / 25 °C AND 1 atm / 100 kPa / 101 kPa / 105 Pa / 1 bar
What is meant by the term average bond enthalpy (2 marks)
(Average enthalpy change) when one mole of bonds ✓ of (gaseous covalent) bonds is broken
Explain the term stereoisomerism
Same molecular formula AND Different structural formulae
What are the conditions when a carboxylic acid reacts with an alcohol to form an ester
Heat under reflux
Describe in terms of orbital overlap the similarities and differences between the bonding in Kekule model and the delocalised model of benzene (3 marks)
Similarities - Orbital overlap (sideways) overlap of p orbitals • π bond π bond/system/ring above and below (bonding (C) atoms/ring/plane) Difference Kekule has: alternating π bonds OR 3 π bonds / localised (π electrons) / overlap in one direction / 2 electrons in π bond AND Delocalised has: π ring (system) / all p orbitals overlap OR (π electrons) spread around ring / overlap in both directions / 6 electrons in π bond /
Describe 2 pieces of evidence to support the delocalised model of benzene (2 marks)
Bond length (C–C) bond length is between single (C–C) and double bond (C=C) OR all (C–C) bond lengths are the same ΔH hydrogenation ∆H hydrogenation less (exothermic) than expected Resistance to reaction Benzene is less reactive than alkenes OR bromination of benzene requires a catalyst/halogen carrier OR benzene does not react with/decolourise bromine (at room temperature) OR benzene reacts by substitution OR benzene does not (readily) react by addition
What is meant by heterolytic fission
Heterolytic one (bonded) atom/O receives both/2 electrons Fission Breaking of a covalent bond OR breaking of C-O bond
Define relative isotopic mass
The mass of an atom of the isotope compared with 1/12th the mass of an atom of carbon-12
Define relative atomic mass of an element
The weighted mean mass of an atom of an element compared with 1/12th the mass of an atom of carbon-12
Define relative molecular mass of a substance
The weighted mean mass of a molecule of that substance compared to 1/12th of the mass of an atom of carbon-12
Define relative formula mass of a substance
The average mass of a formula unit of that substance compared to 1/12th of the mass of an atom of carbon-12
Give chemical explanations for the following statements. The carbon–carbon bonds in benzene are all the same length
π bonds in benzene are delocalised
The graph shows that rate of reaction decreases over time, explain why in terms of collision theory (2)
• Reactant concentration decreases • So there’s less frequent successful collisions
Explain how a catalyst increases the rate of reaction (2)
• Catalyst lowers activation energy • Greater proportion of molecules have energy greater than the activation energy
Describe and explain the effect of increasing the pressure on the rate of reaction(2)
(Increase in pressure) increases the rate and because molecules are closer together… (1) … so there are more collisions per unit time (1)
Explain why use if catalyst reduces energy demands and benefits the environment (2)
Lower temperatures / less heat / less thermal energy * Less fossil fuels / oil / coal / gas / non-renewable fuels * Reduces CO2 emissions