AS AQA Chemistry (New Spec) Flashcards

Description

A selection of exam style questions covering all topics of the new AQA AS level specification, but with overlap with other courses
Lucy Frances
Flashcards by Lucy Frances, updated more than 1 year ago
Lucy Frances
Created by Lucy Frances almost 6 years ago
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Resource summary

Question Answer
Describe and explain factors affecting the strength of metallic bonding Number 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
Explain why 2,2-dichloro-3-methylpentane is a structural isomer of 2,2-dichlorohexane Same molecular formula/same number and type of atoms Different structural formula/different displayed formula
Explain, in terms of electronegativity, why the boiling point of H2S2 is lower than that of H2O2 Oxygen is much more electronegative than sulfur Hydrogen bonds are formed in H2O2 and not in H2S2 Strongest type of intermolecular force
What is electronegativity? The relative tendency of an atom to attract a bonding pair of electrons in a covalent bond
In 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 this C-Br (bond) breaks more readily than (the) C-Cl (bond) C-Br bond enthalpy/bond strength is less than that for C-Cl
Bromotrifluromethane 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
State one condition necessary for the initiation of a free radical subsitution Ultraviolet/UV/sunlight T>100/high temperature
State Le Chatelier's principle If a system in dynamic equilibrium is disturbed the equilibrium shifts in the direction that tends to reduce the disturbance
Suggest why graphene is an excellent conductor of electricity Each carbon atom is only bonded to three others Delocalised electrons Move and carry a charge
Predict the type of crystal structure of solid zinc fluoride and explain why its melting point is so high Ionic Strong electrostatic attraction Oppositely charged ions
What is an oxidising agent? A substance that tends to bring about oxidation by being reduced and gaining electrons
How 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
State and explain the bond angle in the BF4- ion 109.5 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
State what is meant by the term activation energy The minimum energy that a particle needs to react
Explain why a catalyst has no effect on the position of equilibrium Provide an alternative route Lower activation energy Increase rate of reaction Increase in rate is equal for both forward and backward reactions
Give two features of a reaction at equilibrium Constant concentration Both forward and backward reactions occur at an equal rate
Explain why barium is more reactive than calcium Barium 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
Water forms hydrogen bonds which influences its properties. Explain what is meant by hydrogen bonding and explain two anomalous properties of water resulting from hydrogen bonding A 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
Explain how Van der Waal's forces are formed Uneven distribution of electrons Instantaneous dipole on one atom Causes induced dipole on the other atom
Why does electronegativity decrease down a group? Atomic radius increases Increased electron shielding Decreased nuclear attraction
The boiling point of group 7 elements increases down the group. Explain this trend Van 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
What is ionisation energy The minimum amount of energy required for one mole of atoms to lose one mole of electrons in a gaseous state (KJmol-1)
Why does electronegativity increase across a period? Number of protons increases Increased nuclear attraction Decreased atomic radius
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