enthalpy Flashcards
enthalpy change
reactants-products
is enthalpy change of vaporisation endothermic or exothermic
endothermic as energy is required to overcome London forces
average bond enthalpy
average enthalpy change when one mole of bonds is broken in gaseous molecules
formation
one mole of compound fromed from its elemnts
combustijn
one mole of compound competely combusted in o2
neutralisation
acid and alkali react to porduce one mole of water
Entropy
Measure of disorder in a system
Predict how enthalpy changes of hydration of F- and Cl- would differ
Enthalpy of hydration of F- is more negative/exothermic because it has a smaller size (or if it has greater charge)
F- has a greater attraction to H2O
Is it feasible at all temperatures
🔺G = always negative at all temrpatures
Explain why operational conditions used by industry may be different from those required for a maximum equilibrium yield
- high temp to increase rate
- high pressure is expensive to generate
- high/low pressure/temp for maximum yield.
- catalyst increases rate
If excess of one of the reactants is used, explain in terms of Kc how equilibrium yield of product would be different
Kc does not change with concentration
Concentration of the excess reactant is greater/denominator of Kc expression is greater
Yield of product increases
Numerator of Kc expression increases to restore Kc value
Suggest why chemist is concerned about increasing proportion of H2 that reacts rather than proportion of N2 that reacts
N2 obtained from air
H2 must be manufactured/does not occur naturally
explain dissolving
entropy increases
TS>H
