Lattice Energy Flashcards
What is lattice energy?
Lattice energy is the enthalpy change when 1 mole of an ionic compound is formed from its gaseous ions under standard conditions.
Strictly speaking what do the values given usually for lattice energy refer to ?
Lattice enthalpy
Is there any problem in using values for lattice enthalpy rather than lattice energy?
No because the difference between them is small enough to not be significant.
What is the equations that describe lattice energy of NaCl
The following equation describes the lattice energy of NaClNa+(g)+Cl-(g)—>NaCl(s) ΔH(latt)=-787 kJmol-1
Why is lattice energy always exothermic?
Because the ions are bonded together in it which releases energy.
What does the large expthermic value of the lattice energy shows us?
The large exothermic value of the lattice energy shows that the ionic lattice is very stable with respect to its gaseous ions.
What does more exothermic energy indicate?
The more exothermic the lattice energy, the stronger the ionic bonding in the lattice.
If it’s impossible to determine the lattice energy of a compound by a single direct experiment than how we calculate the lattice energy?
We can calculate a value for lattice energy using several experimental values and an energy cycle called a Born–Haber cycle.
What is lattice energy exactly?
Lattice energy is the internal energy change when 1 mole of an ionic compound is formed from its gaseous ions at 298K.
What is standard enthalpy change of atomisation?
It is enthalpy change when 1 mole of gaseous atoms is formed from its element under standard conditions.
How can the standard enthalpy change of atomisation of chlorine be shown using Chlorine?
1/2Cl2(g)—>Cl(g) ΔHat(with the symbol for standard conditions)=+122 kJmol-1
Why are values of standard enthalpy change of atomisation always positive(endothermic)?
It is because energy must be supplied to break the bonds holding the atoms in the element together.
What is electron affinity?
The energy change occurring when a gaseous non-metal atom accepts one electron is called the electron affinity.
What is first electron affinity?
The first electron affinity, ΔH —O , is the enthalpy change when 1 mole of electrons is added to 1 mole of
gaseous atoms to form 1 mole of gaseous 1– ions under standard conditions.
What is second electron affinity(EA2)
The enthalpy change when 1 mole of electrons is added to 1 mole of gaseous 1- ions to form 1 mole of gaseous 2- ions under standard conditions.
What equation represents the first electron affinity of Chlorine?
Cl(g)+e- —>Cl-(g) EA1=-348kJmol-1
What is the enthalpy change for first electron affinity like:exothermic or endothermic?
Exothermic
What electron affinities are always endothermic from successive electron affinities in the CIE 9701 syllabus?
Second and third
How is the overall enthalpy change in forming an oxide ion,O2-, from an oxygen atom found,
By adding together the first and second electron affinities.
What are the trends in electron affinities in periodic table?
a maximum at Group 17 but the pattern is not always clear. There is no clear pattern in electron affinities down many groups apart from Groups 16 and 17. There is a trend to have less negative (less exothermic) electron affinities as you go down the group, apart from the first member in the group.
What does the value of first electron affinity depend on?
The value of the first electron affinity depends on the attraction between the added electron and the positively charged nucleus. The stronger the attraction, the greater the amount of energy released.
What are the factors influencing electron affinity?
-The greater the nuclear charge, the greater the attractive force between the nucleus and the outer electrons.
-The further away the outer shell electrons are from the positive nuclear charge, the less the attractive force between the nucleus and the outer shell electrons is.
-The greater the number of electron shells, the greater the power of inner shell electrons to shield the outer shell electrons from the nuclear charge.
