Karteikarten
AS AQA Chemistry (New Spec) Flashcards
Karten in diesem Stapel (23)
- 1Describe and explain factors affecting the strength of metallic bondingNumber of protons - The more protons in the cations, the stronger the electrostatic forces of attraction
Number of delocalised electrons - The more, the greater the electrostatic attraction
Size of the ion - Electron shielding
- The smaller the ion the greater the electrostatic attraction - 2Explain why 2,2-dichloro-3-methylpentane is a structural isomer of 2,2-dichlorohexaneSame molecular formula/same number and type of atoms
Different structural formula/different displayed formula - 3Explain, in terms of electronegativity, why the boiling point of H2S2 is lower than that of H2O2Oxygen is much more electronegative than sulfur
Hydrogen bonds are formed in H2O2 and not in H2S2
Strongest type of intermolecular force - 4What is electronegativity?The relative tendency of an atom to attract a bonding pair of electrons in a covalent bond
- 5In the upper atmosphere it is more likely for CBrF3 to produce bromine atoms than it is for CClF3 to produce chlorine atoms. Suggest one reason for thisC-Br (bond) breaks more readily than (the) C-Cl (bond)
C-Br bond enthalpy/bond strength is less than that for C-Cl - 6Bromotrifluromethane is formed when trifluromethane reacts with bromine CHF3 + Br2 --> CBrF3 + HBr This reaction is a free radical substitution similar to that of methane with chlorine Write an equation for each of the following steps in the mechanism for the reaction of CHF3 with Br2 (i) initiation step (ii) first propagation step (iii) second propagation step (iv) a termination step(i) Br2 --> 2Br*
(ii) Br* + CHF3 --> *CF3 + HBr
(iii) Br2 + *CF3 --> CBrF3 + Br*
(iv) 2*CF3 --> C2F6 /
2Br* --> Br2 /
Br* + *CF3 --> CBrF3 - 7State one condition necessary for the initiation of a free radical subsitutionUltraviolet/UV/sunlight
T>100/high temperature - 8State Le Chatelier's principleIf a system in dynamic equilibrium is disturbed the equilibrium shifts in the direction that tends to reduce the disturbance
- 9Suggest why graphene is an excellent conductor of electricityEach carbon atom is only bonded to three others
Delocalised electrons
Move and carry a charge - 10Predict the type of crystal structure of solid zinc fluoride and explain why its melting point is so highIonic
Strong electrostatic attraction
Oppositely charged ions - 11What is an oxidising agent?A substance that tends to bring about oxidation by being reduced and gaining electrons
- 12How can aqueous ammonia be used to distinguish between chloride, bromide and iodide ions?Chloride ions dissolve in dilute ammonia
Bromide ions dissolve in concentrated ammonia/partially soluble in dilute ammonia
Iodide ions are insoluble in ammonia - 13State and explain the bond angle in the BF4- ion109.5
tetrahedral
Four bonded electron pairs spread equally around the boron atom
Repel each other to maximise distance between them
Get as far away from each other as mathematically possible - 14State what is meant by the term activation energyThe minimum energy that a particle needs to react
- 15Explain why a catalyst has no effect on the position of equilibriumProvide an alternative route
Lower activation energy
Increase rate of reaction
Increase in rate is equal for both forward and backward reactions - 16Give two features of a reaction at equilibriumConstant concentration
Both forward and backward reactions occur at an equal rate - 17Explain why barium is more reactive than calciumBarium atoms are larger
Barium atoms have more shielding
Shielding outweighs increase in nuclear charge
Barium electrons are lost more easily/less energy required/ionisation energy decreases - 18Water forms hydrogen bonds which influences its properties. Explain what is meant by hydrogen bonding and explain two anomalous properties of water resulting from hydrogen bondingA hydrogen bond is the electrostatic attraction between two polar groups that occurs when a hydrogen atom experiences the electrostatic field of another highly electronegative atom nearby
Ice is less dense than water - H bonds create an open lattice
High melting/boiling point - H bonds are very strong
High surface tension - Strength of H bonds across the surface - 19Explain how Van der Waal's forces are formedUneven distribution of electrons
Instantaneous dipole on one atom
Causes induced dipole on the other atom - 20Why does electronegativity decrease down a group?Atomic radius increases
Increased electron shielding
Decreased nuclear attraction - 21The boiling point of group 7 elements increases down the group. Explain this trendVan der Waal's forces/induced dipole interactions
Number of electrons increases
Van der Waal's increase down the group
Down the group more energy is required to break the forces - 22What is ionisation energyThe minimum amount of energy required for one mole of atoms to lose one mole of electrons in a gaseous state (KJmol-1)
- 23Why does electronegativity increase across a period?Number of protons increases
Increased nuclear attraction
Decreased atomic radius
Informationen
- Beschreibung
- A selection of exam style questions covering all topics of the new AQA AS level specification, but with overlap with other courses
- Erstellt von
- Lucy Frances
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