Thermodynamics general questions Flashcards
Explain why the bond enthalpy of a Cl-Cl bond is greater than that of Br-Br bond
Cl is a smaller atoms
So attraction between the nucleus and bond pair is stronger
Suggest why the electron affinity of chlorine is an exothermic change
Net attraction between the chlorine nucleus and the extra electron
The freezing of water is an exothermic process. Give one reason why the temperature of a sample of water can stay at a constant value of 0 degrees Celsius when it freezes.
The heat given out escapes
A calculation of the enthalpy of lattice formation of silver iodide based on a perfect ionic model gives a smaller numerical value than the value calculated by theoretical model. Explain this difference.
AgI has covalent character
Bonds holding the lattice together are stronger
In term of electrostatic forces, suggest why the electron affinity of fluorine has a negative value
There is an attraction between the nucleus (and added) electron
Energy is released (when the electron is gained)
Suggest why the electron affinity of chlorine is an exothermic change
Net attraction between the chlorine nucleus and extra electron
State what is meant by the term enthalpy change
Heat energy change at constant pressure
Suggest why the second electron affinity of sulphur is an endothermic process
The negative S- ion repels the electron being added
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 ions are smaller than bromide ions
so the force of attraction between chloride ions and water is stronger
chloride ions attract the delta positive on hydrogen of water
Suggest why hydration of the chloride ion is an exothermic process.
Water is polar
Chloride ions attract the delta positive on hydrogen in water
Explain the interactions between water molecules and fluoride ions when the fluoride ions become hydrated.
Water is polar
Fluoride ions attract the delta positive on hydrogen
Explain why the lattice dissociation enthalpy of magnesium chloride is greater than that of calcium chloride
Magnesium ion is smaller
Attraction between the ions is stronger (magnesium ion and chloride ion)
Explain why the lattice dissociation enthalpy of magnesium oxide is greater than that of magnesium chloride.
The oxide ion has a greater charge
So it attracts the magnesium ion more strongly
Energy is released when a magnesium ion is hydrated because magnesium ions attract water molecules.
Explain why magnesium ions attract water molecules.
Water is polar
Mg 2+ ions attracts negative O on water molecules
Suggest why a value for the enthalpy of solution of magnesium oxide is not found in any data books.
Magnesium oxide reacts with water/insoluble in water
