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55 Cards in this Set
- Front
- Back
What is the enthalpy change? |
Heat energy change under constant pressure |
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WHat is lattice enthalpy? |
Enthalpy change when 1 mole of a solid ionic lattice is separated into its gaseous ions under standard conditions |
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What is bond dissociation enthalpy? |
Enthalpy change when all the bonds of the same type in 1 mole of gaseous molecules are broken |
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What is enthalpy of atomisation of an element? |
Enthalpy change when 1 mole of gaseous atoms is formed from an elements in its standard state |
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What is enthalpy of atomisation of a compound? |
ENthlapy change when 1 mole of a compound is converted into gaseous atoms |
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What is the enthalpy chang eof solution? |
The enthalpy change when 1 mole of a solute is dissovled in suficent solvent such that no enthalpy change occurs on further dilution (the ions are fully separated and do not interact with one another) |
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What is the purely ionic model? |
Ions are perfectly spherical point charges with charge evenly distributed around them |
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Why is enthalpy of hydration exothermic? |
Water is polar as oxygen is electronegative; positive ions form weak bonds with e=oxygen atom |
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Why are mean bond enthalpies not accurate? |
Taken as a range over diff compoudns; strength of bond varies between compounds; not specific to particular compound; experimental data better |
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What is the issue with lattice enthalpy? |
Cant bea measured directly |
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What is entropy? |
A measure of disorder, numebr f ways particles can be arranged/energy can be shared |
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What are 3 ways of increasing entropy? |
Increase number of particles; Gases move more randomly and quicker dissolving a solid (particles can move freely and not held in one place |
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What is a spontaneous reaction? |
One that occurs with no additional energy input |
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Why does water evaporate? |
Increase in entropy although endothermic |
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Why is sodium more reactive than magnesium |
Sodium only has to lose one eelctron, magnesium has to lose two losing one requires less energy |
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Why is sodium more reactive than magnesium |
More energy required to remove one electron |
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How does sodium react wih water? |
Fizzes and forms a molten ball giving off hydrogen gas |
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How does Magnesium react with cold water? How can you tell that a reaction has happened? |
Very slowly to produce hydroxide and oxygen; weakly alkaline solution formed |
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Why is magnesium only form a weakly alkaline solution? |
Only partly soluble |
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Describe all reactions of period 3 elements with oxygen |
Sodium = yellow flame/vigorous magnesium = brillinat white flame/vigorous aluminium = N/A / slow silicong = N/A / slow phosphorous = brilliant white / spontaneous sulphur = blue/steadily burns |
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How do you produce SO3 ? |
Catalsyt and high temp |
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Why is the melting point of aluminium oxide lower than magnesium oxide? |
Al3+ ion distrots/polarises electron cloud, bond partially covalent and weaker so less energy to separate ions |
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Where do melting points of aluminium oxide and silicon dioxide lie relative to sodium oxide and magnesium |
Both above sodium below magnesium silicon below aluminium |
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Why dont silicon dioxide and aluminiun oxide react with water? |
They are insoluble |
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What is the name given to H2SO3? |
sulfurous acid oro sulfuric(IV) acid |
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How do you demonstrate that aluminium oxide is amphoteric? |
Al2O3 + 3H2O + 2NaOH -----> 2NaAl(OH)4; Al2O3 + 6HCl ----> 2AlCl3 + 3H2O |
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What do reducing agents and oxidising agents do? |
Reeducing agents donate electrons and oxidising agents accept electrons |
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What is a salt bridge? |
A piece of filter paper soaked in aqueous KNO3 that completes the circuit and allows the movement of ions |
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What is the standard electrode potential |
The voltage measured under standard conditions when the half cells si connected to a standard hydrogen electrode |
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What factors affect the electrode potential of a half cell? |
Concentration, perssure, temp |
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How do rechargebable cells work? |
Current supplied; electrons forced opposite way around the circuit; reactions are reversed; none of the substances used up or escape |
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Why cant you recharge a normal dry cell battery? |
Casing oxidised and wears away or a substance escapes |
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What are the pros of rechargeable batteries? |
They are cheaper in the long run; provide more power and can be used in high power devices; less resources used making them and less landfill |
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What are the cons of rechargeable batteries? |
More likely to contain heavy metals and toxic elements; expensive to buy; don't last as long before running out of charge |
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What are the pros of non-rechargeable batteries? |
Cheaper to buy; last longer before running out of charge; less likely to contain heavy metals and toxic elements |
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What are the cons of non-rechargeable batteries? |
Expensive in the long run; more have to be made and more space in landfill;, boh can't provide all that much power |
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Describe a hydrogen-oxygen fuel cell? |
2 platinum electrodes (platinum coating over porous ceramic material); separated by ion exchange membrane to allow movement of ions and not electrons; and in acidic/alkaline electrolyte; electrons forced to move around external circuit |
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What are the advantages of fuel cells? |
Constant supply of electricity as long as constant supply of fuel; onyl waste is water |
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What are the disadvantages of fuel cell? |
Need constant supply of fuel; hydrogen flammable; produced throough electrolysis |
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What is a transition metal? |
A metal that forms one or more stable ions with a partially filled d subshell |
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Why are zinc and scandium not transition metals |
Zn only forms 2+ with full d subshel Sc only forms 3+ with empty d subshell |
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What are the physical properties of transition metals? |
High melting point/high boiling point high density similar ionic radii |
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What are the chemical properties of transition metals/ |
Variable oxidation states form complex ions form coloured ions act as catalysts |
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Why do transition metals have similar chemical proerties? |
Due to incomplete d subshell |
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Why do transition metals have variable oxidation states? |
Energy levels of the 4s and 3d subshell are close together, different amounts of electrons can be lost or gaines using similar amounts of energy |
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What colour is aqueous V2+? |
violet |
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What colour is aqueous V3+? |
Green |
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What colour is aqueous (VO)2+? |
Blue |
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What colour is aqueous (VO2)+? |
Yellow |
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What is a complex ion? |
Transition metal ion surrounded by coordinately bonded ligands |
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What is a co-ordinate bond? |
A covalent bond in which both electrons come from the same atom |
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What is a ligand? |
A species that donates a lone pair of electrons TO A CENTRAL METAL ION |
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What is a unidentate ligand? |
A species that forms only one coordinate bond with a central metal ion |
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What do dashed arrows represnt? |
Bonds sticking out behind the molecule |
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What are the units of Plankcs constant and what is the value? |
Js 6.63*10^-34 |