Unit 3- Chemistry in Society Flashcards
(27 cards)
Bond enthalpies
The amount of energy needed to break one mole of a bond in a gaseous molecule. These are measured in diatomic molecules.
Chromatography
An analytical method where mixtures are separated into their components by partitioning between a stationary and mobile phase. The stationary and mobile phases are solid/liquid in paper and thin layer chromatography, and liquid/gas in gas-liquid chromatography.
Dynamic equilibrium
Achieved when the rates of two opposing processes become equal, so that no net change results.
Endothermic reactions
Reaction which absorb heat energy from the surroundings.
End-point
The point at which the reaction is just complete.
Enthalpy change
For a reaction is defined as the change in heat energy when one mole of reactant is converted to products at constant pressure, and has the symbol deltaH and units of KJ mol-1
Enthalpy of combustion
The Enthalpy change that occurs when one mole of a substance is burned completely in oxygen.
Enthalpy of neutralisation
The energy change when an acid is neutralised to form one mole of water.
Enthalpy of solution
The energy change when one mole of the substance dissolves in water.
Equilibrium
The state reached by a reaction mixture when the rates of forward and reverse reactions have become equal.
Exothermic reactions
Reactions which release heat energy, which is given up to the surroundings.
Feedstocks
A reactant from which other chemicals can be extracted or synthesised. Feedstocks are themselves derived from raw materials either by physical separation or a chemical reaction.
Hess’s Law
The enthalpy change for a chemical reaction is independent of the route taken providing the starting point and finishing point is the same for both routes.
Ion-electron equations
A half-equation, either oxidisation or reduction, which in combination of the opposite type can be part of a complete redox equation.
Mean bond enthalpies
The Enthalpy change needed to break the covalent bond into gaseous atoms, averaged over the different molecules that the bond can be found in.
Molar volume
The volume occupies by one mole of a substance. For gases, the units used are l.mol-1
Oxidation
A loss of electrons by a reactant in any reaction, or in organic chemistry, an increase in the oxygen to hydrogen ratio in a molecule.
Oxidising agent
A substance which accepts electrons (and is reduced in the process)
Potential energy diagram
Shows the enthalpy of reactants and products and the enthalpy change durning a chemical reaction.
Reducing agent
A substance which donates electrons (and is oxidised in the process)
Reduction
The gain of electrons by a species, or, in organic chemistry, a reaction which results in a decrease in the oxygen to hydrogen ratio in a molecule.
Retention time
The time takes for an individual peak to traverse the gas-liquid chromatographic column after the injection time.
Specific heat capacity
Relates the energy change in a liquid to the change in temperature.
Standard solution
A solution of accurately known concentration
