OCR Chemi unit 5 definitions

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Rate of reaction
is the change in concentration of a reactant or product per unit of time
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Initial rate of reaction
is the change in concentration of a reactant or product per unit of time at the start of the reaction when t=0
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th order with respect to a reactant
is the power to which the concentration of the reactant is raised in the rate equation
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the rate constant, k,
is the constant that links the rate of reaction with the concentration of the reactants raised to the powers of their orders in the rate equation
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the half-life
of a reactant is the time taken for the concentration of the reactant to reduce by half
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a reaction mechanism
is a series of steps that together, make up the overall reaction
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the rate determining step
is the slowest step in the reaction reaction mechanism of a multi-step reaction
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an intermediate
is a species formed in one step of a multi-step reaction that is used up in a subsequent step, and is not seen as either a reactant or a product of the overall reaction
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Equilibrium law
states that for the equilibrium
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a dynamic equilibrium
exists in a closed system when rate of the forward reaction is equal to the rate of the backwards reaction
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a homogeneous equilibrium
is an equilibrium in which all the species making up the reactants and products are in the same state
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a heterogeneous equilibrium
is an equilibrium in which species making up the reactants and products are in different physical states
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Bonsted-Lowry acid
is a proton, H+, donor
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Bronsted-Lowry base
is a proton, H+ acceptor
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an alkinli
is a base that dissolves in water forming OH- (aq) ions
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Neutralisation
is a chemical reaction in which an acid and a base react together to produce a salt and water
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An acid-base pair
is a pair of two species that transform into each other by gain or loss of a proton
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pH
=log[H+(aq)]
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[H+(aq)]
= 10
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A strong acid
is an acid that completely dissociates in solution
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a weak acid
is an acid that only partially dissociates in solution
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pK
=-log K
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K
=10
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a buffer solution
is a mixture that minimises pH changes on addition of small amounts of acid or base
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the equivalence point
is the point in a titration at which the volume of one solution has reacted exactly with the volume of the second solution. This matched the stoichiometry of the reaction taking place
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end point
is the point in a titration at which there are equal concentrations of the weak acid and conjugate base forms of the indicator. The colour at the end point is midway between the colours of the acid and conjugate base forms
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the standard enthalpy change of neutralisation
is the energy change that accompanies the neutralisation of an aqueous acid by an aqueous base to form one mole of H O(l) under standard conditions
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Lattice enthalpy
is the enthalpy change that accompanies the formation of one mole of an ionic of an ionic compound from its gaseous ions under standard conditions
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Hess' Law
states that if a reaction can take place by more than one route and the initial and final conditions are the same, the total enthalpy change is the same for each route.
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standard enthalpy change of formation
is the enthalpy change that takes place when one mole of a compound is formed from its constituent elements in their standard states under standard conditions
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enthalpy change of atomisation
is the enthalpy change that takes place when one mole of gaseous atoms forms from the element in its standard state
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first ionisation energy
is the enthalpy change accompanying the removal of one electron from each atom in one mole of gaseous atoms to for one mole of gaseous 1+ ions
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second ionisation energy
is the enthalpy change accompanying the removal of one electron from each atom in one mole of gaseous 1+ ions to for one mole of gaseous 2+ ions
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first electron affinity
is the enthalpy change accompanying the addition of on electron to each atom in one mole of gaseous atoms to form one mole of gaseous 1- ions
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second electron affinity
is the enthalpy change accompanying the addition of on electron to each atom in one mole of gaseous 1- ions to form one mole of gaseous 2- ions
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standard enthalpy of solution
is the enthalpy change that takes place when one mole of a compound is completely dissolved in water under standard conditions
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standard enthalpy change of hydration
is the enthalpy change that takes place when one mole of isolated gaseous ions is dissolved in water forming one mole of aqueous ions under standard conditions
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entropy, S,
is the quantitative measure of the degree of disorder in a system
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standard entropy change of reaction, S ,
is the entropy change that accompanies a reaction in the molar quantities expressed in a chemical equation under standard conditions, all reactants and products being in their standard states
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free energy change
is the balance between enthalpy, entropy and temperature for a process:
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oxidation
is the loss of electrons, or an increase in oxidation number
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reduction
is the gain of electrons, or a decrease in the oxidation number
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standard electrode potential of a half cell
is the e.m.f of a half cell compared with a standard hydrogen half cell, measured at 298K with solution concentrations of 1 mol dm and a gas pressure of 100kPa
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transition element
is a d block elements that forms an ion with a incomplete d sub shell
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a complex ion
is a transition metal ion bonded to one of more ligands by coordinate bonds (dative covalent bonds)
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ligand
is a molecule or ion that can donate a pair of electrons with the transition metal ion to form a coordinate bond
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coordination number
os the total number of coordinate bonds formed between a central metal ion and its ligands
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sterioisomers
are species with the same structural formula but with a different arrangement of the atoms in space
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ligand substitution
is a reaction in which one ligand in a complex ion is replaced by another ligand
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stability constant, K
is the equilibrium constant existing between a transition metal ion surrounded by water ligands and the complex formed when the same ion has undergone a ligand substitution
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Other cards in this set

Card 2

Front

Initial rate of reaction

Back

is the change in concentration of a reactant or product per unit of time at the start of the reaction when t=0

Card 3

Front

th order with respect to a reactant

Back

Preview of the front of card 3

Card 4

Front

the rate constant, k,

Back

Preview of the front of card 4

Card 5

Front

the half-life

Back

Preview of the front of card 5
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