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Frage | Antworten |
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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