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Flashcards by jasmin.sahota, updated more than 1 year ago
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Created by jasmin.sahota
over 12 years ago
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| Question | Answer |
| standard enthalpy of an element is... | zero |
| H2(g) + 0.5O2(g)--> H20(l) what is this an example of? | standard molar enthalpy of formation |
| the standard enthalpy of atomisation is... | the enthalpy change which accompanies the formation of one mole of gaseous atoms from the element in its standard state under standard conditions |
| Mg(s) -->Mg(g) is an example of... | the standard enthalpy of atomisation |
| definition of first ionisation energy... | is the standard enthalpy change when one mole of gaseous atoms is converted into a mole of gaseous ions each with a single positive charge. |
| Na(g) --> Na+(g) + e- is an example of... | first ionisation energy |
| definition of second ionisation energy | refers to the loss of a mole of electrons from a mole of singly positively charged ions |
| Na+(g) --> Na2+(g) + e- is an example of.. | second ionisation energy |
| O(g) + e- ---> O-(g) is an example of | first electron affinity note it refers to single atoms, not oxygen molecules, O2 |
| definition of lattice formation enthalpy is... | is the standard enthalpy change when one mole of solid ionic compound is formed from it's gaseous ions |
| O-(g) + e- --> O2- (g) is an example of | the second electron affinity |
| Na+(g) + Cl-(g) --> NaCl(s) is a definition of | lattice formation enthalpy |
| (Na+) + aq --> Na+ (aq) is an example of | enthalpy of hydration |
| definition on the enthalpy of solution is... | is the standard enthalpy change when one mole of solute dissolves completely in sufficient solvent to form a solution in which the molecules or ions are far enough apart not to interact with each other. |
| NaCl(s) + aq --> Na+(aq) + Cl-(aq) is an example of | enthalpy of solution |
| definition of mean bond enthalpy | is the enthalpy change when one mole of gaseous molecules each breaks a covalent bond to form two free radicals, averaged over a range of compounds |
| standards conditions = | 100kPa and 298k |
| ionic bonding is between | metal and non metal ions |
| the metal ions in ionic compounds are... | positively charged ions that have a stable outer shell of electrons |
| the non-metal ions in an ionic compound are.. | negatively charged ions with a stable outer shell of electrons |
| Hess's law states | the total enthalpy change for a chemical reaction is the same whatever route is take |
| Born - Haber cycle is | a thermochemical cycle that includes all the enthalpy changes involved in the formation of an ionic compound |
| A born-haber cycle starts with | the elements in there standard states, so starts from zero |
| draw the born haber cycle for NaCl | |
| draw the born haber cycle for MgCl when we know 1. delta Hf = -641kJmol-1 2. delta H at (Mg) = +148 kJmol-1 3. first IE (Mg) = +738Kjmol-1 4. second IE (Mg) = +1451 Kjmol-1 5. atomisation of Cl = +122Kjmol-1 6. first EA of Cl = -349kJmol-1 7. lattice formation = -2524kJmol-1 | |
| all first electron affinities of all element are negative because... | the added electron is attracted by the nuclear charge. |
| looking at the trends in lattice energy, a larger ion means... | a smaller lattice enthalpy |
| why does a larger ion lead to a smaller lattice enthalpy... | because the opposite charges do not approach each other as closely when the ions are larger. |
| the lattice enthalpy increases with the size of the charge, why? | because ions with double the charge give out roughly twice as much energy when they come together |
| negative delta H is a clue as to whether a reaction is | spontaneous or not |
| gases are more ..... than liquids | random because of the arrangement of their particles |
| the randomness of a system is called | entropy |
| is the particles of the products is more disordered than the reactants then the entropy change is... | positive |
| what has a larger entropy, liquids, gases, or solids? | gases>liquids>solids |
| units of entropy are | JK-1mol-1 or kJK-1mol-1 |
| the entropy change for a reaction can be calculated by | adding all the entropies of the products and subtracting the sum of the entropies of the reactants. |
| what are the two factors that dictate whether a reaction is feasible? | enthalpy change and entropy change |
| is delta G = negative this means? | the reaction is feasible |
| if delta G = positive this means? | the reaction is not feasible |
| gibbs depends on temperature therefore | some reactions may be feasible at one temperature and not at another |
| when delta G = 0 what does this mean? | this is the point at which the reaction is feasible. |
| enthalpy and entropy tell us nothing about the rate of the reaction.. why? | because there may be a high activation energy barrier |
| delta S is | the sum of the entropies of the products - the sum of the entropies of the reactants |
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