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19 Cards in this Set

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Standard enthalpy of combustion

The enthalpy change, under standard conditions when one mole of a substance is completely combusted in oxygen, with all reactants and products in their standard states.

Standard conditions

100 kPa and 298 K

Standard enthalpy of formation

The enthalpy change under standard conditions when one mole of a compound is formed from its elements with all reactants and products in their standard state.

Calorimetry

q = m c ^T


^H = -q / moles


q = the heat energy change

Enthalpy change

^H = E ^Hf products - E ^Hf reactants


^H = E ^Hc reactants - E ^Hf products

Mean bond enthalpy

...is the average of several values of the bond taken from a range of different compounds.

Enthalpy change equation

^H = E mean bond enthalpy reactants - E mean bond enthalpy products



(Bonds broken - bonds formed)

Rate of reaction

Change in concentration of a substance in unit time

Factors effecting rate of reaction

Concentration, surface area, temperature and a catalyst.


Concentration of the reactant naturally declines as it is used up, meaning rate of reaction declines.

Activation energy

Is the minimum energy required for a reaction to occur

Catalyst

A substance which alters the rate of reaction without being consumed itself, by providing an alternative reaction pathway with a lower activation energy

Le Chatelier's principle

A system in equilibrium will respond to oppose any change imposed upon it.

Factors effecting equilibrium

Concentration, pressure, temperature and a catalyst.

Oxidation and oxidising agents

Oxidation is the process of electron loss. Oxidising agents are electron acceptors (electrophiles).

Reduction and reducing agents

Reduction is the gain of electrons. Reducing agents are electron donors (nucleophiles)

Halogen trends; electronegativity, boiling point, oxidising power

Electronegativity decreases due to increasing atomic radius and more filled energy shells meaning the outer electron is less likely to be able to withdraw electron density from a covalent bond.


Boiling point increases due to stronger van der waals between the larger molecules.


Oxidising power decreases.

Displacement recations

Chlorine displaces bromide and iodide. Bromine displaces iodide. Iodine shows no change. You can tell which has been displaced by the colour of the solution: chlorine: pale green, bromine: yellow,brown, iodine: brown.

Halide reducing agents

Power of reducing agents increases, shown by their reaction with sulphuric acid.


NaF: no redox but will produce HF


NaCl: no redox but will produce HCl


NaBr: produces HBr, SO2 and Br2


NaI: produces HI, SO2, H2S, S and I2

Identification of halides

Acidified silver nitrate then dilute ammonia then concentrated ammonia.


F- no change as silver fluoride is soluble


Cl- white precipitate, soluble in dilute


Br- cream precipitate, soluble in concentrated


I- yellow precipitate, insoluble