Unit 2 Glossary Flashcards
Buffer solution
A solution in which the pH remains approximately constant when small amounts of acid or base are added.
Closed system
No exchange of matter or energy with its surroundings
Conjugate acid
For every base, there is a conjugate acid formed by the gain of a proton. (H+)
Conjugate base
For every acid, there is a conjugate base formed by the loss of a proton. (H+)
Diprotic
An acid which is able to produce two H+ ions from each molecule.
Dynamic Equilibrium
Achieved when the rates of two opposing processes become equal, so that no net change results.
End point
end point of a titration is the point at which the reaction is shown to be complete. This is usually signalled by the change in colour of an indicator.
Entropy
The entropy of a system is the degree of disorder of the system. The greater the disorder, the greater the entropy. Low entropy is associated with strongly ordered substances.
Equivalence Point
In a titration experiment. Reached when the reaction between the titrant (added from the burette) and the titrate (in the flask) is just complete.
First law of thermodynamics
The total energy of the Universe is constant; energy cannot be created or destroyed.
Gibbs standard free energy
The standard Gibbs free energy change for a reaction is related to the standard enthalpy and entropy changes.
Hess’s Law
The overall reaction enthalpy is the sum of the reaction enthalpies of each step of a reaction.
Enthalpy change is independent of the route taken.
Mean bond enthalpy
An average value that is quoted for a bond that can occur in different molecular environments.
Molar bond enthalpy
The bond enthalpy is the energy required to break one mole of diatomic molecule bonds.
Monoprotic
An acid which is able to produce one H+ ion from each molecule.
Order of a reaction
The power to which the concentration of a particular reactant is raised in the rate equation.
Overall order of reaction
The sum of the powers to which the concentrations of all reactants are raised in the rate equation.
Quantitative reaction
Where the reactants react completely according to ratios in the balanced stoichiometric equation.
Rate constant
In a rate equation, k is the rate constant and has a constant value for a given reaction at a particular temperature.
Rate-determining step
The slowest step in a reaction mechanism, which governs the overall rate.
Rate equation
An equation that displays how the reaction rate depends of the concentration of each reactant.
Reaction Mechanism
The series of simple steps by which a chemical reaction occurs.
Second law of thermodynamics
Total entropy of a reaction system and its surroundings always increases for a spontaneous change
standard conditions
the conditions of a reaction process at a pressure of 1 atmosphere and a specific temperature (298K or 25 degrees)
Standard enthalpy change
the enthalpy change for a reaction in which reactants and products are considered to be in their standard states at a specified temperature.
Standard enthalpy of combustion
the enthalpy change when one mole of a substance is completely burned in oxygen under standard conditions.
Standard enthalpy of formation
Enthalpy change that occurs when one mole of a substance is produced from its elements in their standard states.
Standard solution
A solution with an accurately known concentration. It can be prepared by weighing a primary standard and dissolving it in a known volume of solution, or by titrating against another standard solution.
Standard state
the most stable state of a substance or element under standard conditions.
Third law of thermodynamics
The entropy of a perfect crystal at 0K is zero.
