Module 3 Flashcards
(14 cards)
First Ionisation Energy
The energy required to remove one electron from each atom in one mole of gaseous atoms of an element to form one mole of gaseous 1+ ions.
When testing an unknown solution to identify the anions in it, why is it necessary to add acid before adding barium chloride solution?
The acid removes carbonate ions, which would form a white precipitate of BaCO3 when barium chloride solution was added and give a false positive result for sulphate ions.
State Le Chatelier’s Principle
When the conditions on a system in equilibrium are changed, the equilibrium moves to minimise the effects of the change/ oppose the change.
What is a catalyst and how does it increase the rate of reaction?
A substance that increases the rate of a chemical reaction without being used up in the process. A catalyst provides an alternative route for the reaction with lower activation energy. Thus a greater proportion of molecules have energy greater than or equal to the activation energy.
Standard enthalpy change of combustion
The enthalpy change that takes place when one mole of a substance reacts completely with oxygen (is completely combusted) under standard conditions, with all reactants and products in their standard states.
Standard enthalpy change of formation
The enthalpy change that takes place when one mole of a compound is formed from its elements under standard conditions, with all reactants and products in their standard states.
Standard enthalpy change of neutralisation
The energy change that accompanies the reaction of an acid by a base to form one mole of H₂O(l), under standard conditions, with all reactants and products in their standard states.
What is the order to carry out anion tests in?
Carbonate, sulfate, halide test.
State the conditions of temperature and pressure used for standard enthalpy measurements
298 K/25ºC & 100 kPa
State and explain how the halogen in the haloalkane affects the rate of hydrolysis.
The weaker the bond the faster the reaction
C–F bond is hydrolysed slowest
C–I bond is hydrolysed faster than C–Br
C–I bond is the weakest
C–I has lower bond enthalpy than C–Br
C–Br is broken more easily/readily than C–Cl
C–Hal bond strength decreases down group (7)
Why do successive ionisation energies increase with ionisation number?
radius decreases
AND attraction between (the remaining) electrons and nucleus increases.
Explain how the first ionisation energies of magnesium and aluminium give further details of electron structure.
Mg has outer electron in 3s sub-shell
AND Al has outer electron in 3p sub-shell
3p sub-shell has higher energy than 3s sub-shell.
Explain why the first ionisation energy of strontium is less than the first ionisation energy of calcium.
Atomic radius:
larger atomic radius OR more shells
Effect of nuclear charge / shielding:
Increased nuclear charge outweighed by increased distance / shielding OR more / increased shielding
Nuclear attraction :
less nuclear attraction OR less attraction on electrons.
What colour are the halogens?
Fluorine: a pale yellow-green gas
Chlorine: yellow-green gas. In solution, it appears as a pale green or even colorless depending on the concentration.
Bromine: a red-brown, fuming liquid at room temperature. It also has a pungent odor. When dissolved in water, bromine forms an orange solution. (yellow in a markscheme)
Iodine: a purple-black solid at room temperature. When heated, it sublimes, forming a purple gas. In solution, it appears as a light orange-brown color.
