Term 1 Flashcards
Define (first) electron affinity.
The first electron affinity of an atom is the energy released when 1 mole of electrons is added to 1 mole of gaseous atoms to form 1 mole of gaseous 1- ions. This is always exothermic.
Why does fluorine have an EA less than Chlorine?
Fluorine is a small atom, so when you are putting a new electron into a region of space already crowded with electrons there is a significant amount of repulsion.
Why are second and subsequent EAs endothermic?
You are forcing an electron into an already negative ion so there will be repulsion.
Define lattice enthalpy.
The energy change when one mole of an ionic lattice is formed at 298K and 1atm from its isolated gaseous ions.
What two factors influence lattice enthalpy?
Size of ion and charge of ion. These contribute to the ion’s charge density. The smaller the ion and the higher charged the ion the greater the charge density and vice versa. The greater the charge density the more exothermic the lattice enthalpy.
Define enthalpy change of solution.
The enthalpy change when 1 mole of an ionic substance dissolves in water to give a solution of infinite dilution.
Define enthalpy change of hydration.
The energy change when 1 mole of gaseous ions are dissolved in sufficient water to give an infinitely dilute solution.
Give the equation for Hess’s cycle.
♤H(soln) = €♤H(hyd) - ♤H(lat)
Describe what a born-haber cycle looks like.
Three points:
Top left = ions in gaseous state
Top right = ionic compound (s)
Bottom middle = elements in their standard states
♤H(latt) running left to right at the top
♤Hf from elements to compound
♤H1 from elements to gaseous ions (multiple steps)
Define entropy.
A measure of the ‘disorder’ of a system, and a system becomes more stable when energy is spread around in a more ‘disordered’ state.
Give the Gibbs free energy change equation.
♤G = ♤H - T♤S
In the Gibbs free energy equation, what indicates whether a spontaneous reaction is possible?
♤G is -ve
Give the definitions of Lewis acids and bases.
Lewis acid - electron pair acceptor
Lewis base - electron pair donor
Give the definitions of Brønsted-Lowry acids and bases.
Brønsted-Lowry acid - proton donor
Brønsted-Lowry base - proton acceptor
Define amphoteric
A substance which can act as a base or an acid.
Define amphiprotic.
A substance that can donate or accept an H+ ion.
Give the value of the ionic product of water (Kw)
1×10‐¹⁴ mol² dm‐⁶ at 25°C
Give the equations involving only pH and [H+]
pH = -log[H+]
[H+] = 10^-pH
Give the equation for Ka and how to find pKa.
Ka = [H+]×[A-] / [HA]
pKa = -log(Ka)
How to calculate the pH of a weak acid:
[H+] = root (Ka[HA])
Since: pH = -log[H+]
pH = -log(root(Ka[HA]))
Give the Henderson-Hassalbach equation.
pH = pKa + log ( [base] / [acid] )
Give an eauation for calculating [H+] in terms of Ka, Kw, and [A-].
[H+] = root ( Ka×Kw / [A-] )
Using the ionic product and Ksp, how can we tell if precipitation occurs?
If I.P is greater than Ksp.
What is the order of reaction?
The power to which a concentration is raised in the rate equation.
How can we determine the difference between 1st and 2nd order reaction?
Length of half life is constant for 1st order.
Length of half life increases with decreasing concentration.
Give the Arrhenius equation.
k = Ae^-Ea/RT
Give the trend for thermal stability of carbonates in group 2.
Carbonates become more stable to heat as you go down the group.
Give the trend of thermal stability of the nitrates of group 2.
Nitrates become more stable to heat as you go down the group.
Give the trend for the solubility of group 2 sulphates.
Solubility decreases down the group.
Give the trend of solubility of group 2 hydroxides.
Solubility increases down the group.
