Thermodynamics Flashcards
By describing the nature of the attractive forces involved, explain why the value for the enthalpy of hydration for the chloride ion is more negative than that for the bromide ion
Chloride ion has less shielding and is a smaller molecule
Force of attraction between Cl- ions and water is stronger
Cl- ions attract delta positive H
Write an equation including state symbols for the reaction that has an enthalpy change equal to the lattice dissociation enthalpy of magnesium chloride
MgCl2 (s) -> Mg2+ (g) + 2Cl2-
Suggest why a value for the enthalpy of solution of magnesium oxide is not found in any data books
Forms Mg(OH)2
Sparingly soluble
Use your knowledge of bonding to explain why DeltaH is positive for this process
Energy must be supplied to break
The freezing of water is an exothermic process. Give one reason why the temp of a sample of water can stay at a constant value of 0C when it freezes
Heat energy given out
Explain why the electronegativity of fluorine is greater than the electronegativity of chlorine
Least amount of shielding
Bond pair more strongly attracted to nucleus
Explain why the hydration enthalpy of the fluoride ion is more negative than the hydration enthalpy of chloride
Fluoride ion is smaller so attracts ions more strongly
Explain why the magnitude of deltaG decreases as T increases in this reaction
DeltaS is positive
In terms of electrostatic forces, suggest why the electron affinity of fluorine has a negative value
Attraction between nucleus and electron
Explain why the theoretical enthalpy of lattice dissociation for silver fluride is different from the experimental value that can be calculated using a born haber cycle
Theo - perfectly ionic
Experimental - covalent character
Define the enthalpy of hydration of an ion
Enthalpy change at constant pressure when 1 mol gaseous ion forms aqueous ions
Suggest why hydration of the chloride ion is an exothermic
Water is polar
Cl- attacks water molecules
