Module 3- Periodic table and energy Flashcards
Periodicity
Repeating pattern across different periods
Disproportionation
A reaction where an element simultaneously oxidises and reduces
The activation energy
The minimum energy which particles need to collide to start a reaction
Enthalpy change of reaction
When the number of moles of reactants as specified in the balanced equation react together
Standard enthalpy change of formation of a compound
The enthalpy change when 1 mole of the compound is formed from its elements under standard conditions (298K and 100kpa), all reactants and products being in their standard states
Standard enthalpy of combustion of a substance
The enthalpy change that occurs when one mole of a substance is combusted completely in oxygen under standard conditions. (298K and 100kPa), all reactants and products being in their standard states
Standard enthalpy change of neutralization
The enthalpy change when solutions of an acid and an alkali react together under standard conditions to produce 1 mole of water
Mean bond enthalpy
The Enthalpy change when one mole of bonds of (gaseous covalent) bonds is broken (averaged over different molecules)
Hess’s law
Total enthalpy change for a reaction is independent of the route by which the chemical change takes place
initial rate
Rate at the start of the reaction where it is fastest
Catalyst
increase reaction rates without getting used up
Dynamic equilibrium
When forward and backward reactions are occurring at equal rates. The concentrations of reactants and products stays constant and the reaction is continuous
Period
a horizontal trend in the periodic table. Elements show trends in properties across a period.
Group
a vertical column in the periodic table. Elements in a group have similar chemical properties and their atoms have the same number of electrons in their outer-shell.`
Periodicity
is the regular variation of elements with atomic umber and position in the periodic table.
Thermal decomposition
breaking of chemical substance with heat into at least 2 chemical substances.
Displacement reaction
is a reaction in which more reactive element displaces a less reactive element from an aqueous solution of the latters ions.
Disproportionation
is the oxidation and reduction of the same element in a redox reaction
Precipitation reaction
is the formation of a solid from a solution during a chemical reaction. Precipitates are often formed when 2 aqueous solutions are mixed together.
Enthalpy, H
The heat energy stored in a chemical system
Exothermic
When the enthalpy is smaller at then end of a reaction than at the beginning. Resulting in heat loss. Deltah -ve.
Endothermic
When the enthalpy is greater at then end of a reaction than at the beginning. Resulting in heat being taken in. Deltah +ve
Activation energy
Minimum energy required to start a reaction by the breaking of bonds.
Enthalpy profile diagram
Shows the enthalpy of the reactants and products along with the activation energy and enthalpy change.
Standard conditions
Pressure of 100kpa and Temperature of 298K. In solution concentration of 1M.
Standard state
The state we find a substance in under standard conditions.
Standard enthalpy change of reaction
Is the enthalpy change that accompanies the moles given in a balanced equation are reacted under standard conditions and in standard states
Standard enthalpy change of combustion
Is the enthalpy change when one mol of reactant is burned completely in oxygen under standard conditions
Standard enthalpy change of formation
Is the enthalpy change when 1 mol of product is formed from its constituent elements in standard states under standard conditions.
Specific heat capacity, C
Energy required to heat 1g of substance by 1K.
Bond enthalpy
Is the enthalpy change when 1 mol of given bonds is broken by homolytic fission in a gaseous state.
Hess’ Law
“if a reaction can take place by more than 1 route and the initial and final conditions are the same, the total enthalpy change is the same for each route.”
Rate of reaction
The change in concentration of a reactant or product in a given time.
Catalyst
A species than lowers the activation energy of a reaction by providing an alternate route but is not used itself.
Boltzmann distribution
Is the distribution of energies of molecules within a sample at a given temperature.
Dynamic equilibrium
An equilibrium in a closed system where the rate of forward reaction equals that of the reverse reaction leaving constant concentrations of products and reactants
Le chatelier’s principle
When a change is imposed on a system in dynamic equilibrium the position of the equilibrium will change to minimise the change.
