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What is a titration?
An increment of reagent solution (titrant) added to an analate solution until a reaction is complete
How is the analyte quantity calculated?
From the quantity of the titrant required.
What are the requirements of the titration?
The reaction (analyte and titrant) has a large K value that rapidly proceeds.
What is the endpoint?
The measurable estimate of the equivalence point, marked by a sudden change in signal.
What are the types of Titration?
Direct Titration ad Back Titration.
What is a direct titration>
The tirant is added to analyte until reaction is complete.
What is a back titration?
Known excess of reagent (titrant) is added to analyte solution, then the excess is titrated with a second standard reagent.
What is the indicator?
A compound with physical properties that change abruptly near the equivalence point and the change is measurable
i.e. color change
What is a standardized reagent?
Sometihing added to an unknow quanitity of analyte until the analyte is judged to be exactly consumed by the reaction. A reagent with a known concentration used in titrations to accurately measure the amount of analyte present.
What must be known to solve the analyte concentration?
The stoichiometry or the known moles of titrant to the moles of analyte.
What is a primary standard?
A highly pure substance used to determine the concentration of a solution. It has a known and stable composition, making it ideal for calibrating other reagents.
True or False:
Many reagents used as titrants (HCl, KMnO4, etc.) are not available as primary standards.
True. Many common titrants lack the purity and stability required to be classified as primary standards.
How do we standardize reagents that are not available as primary standards?
We titrate it with a well known primary standard, if possible.
What is a titration curve?
A graph showing how the concentration of a reactant varies as titrant is added.
What does the concentration vary over?
The orders of magnitude plotted as a p function
i.e. pX = -log (X)
What do high values of pX indicate?
Low concentrations of X
What happens to the equilibrium of Iron (III) and thiocyanide (SCN) when Potassium Nitrate (KNO3) is added as a salt.
increases the ionic strength of the solution, which can shift the equilibrium position of the reaction between Iron (III) and thiocyanide, potentially favoring the formation of the complex ion, iron thiocyanate.
How does the KNO3 salt that ios “inert” shift equilibrium?
By having a charge shielding effect on the compounds it interacts with.
What are ions and molecules surrounded by in an aqueous solution?
Water molecules, creating a hydration shell.
How does water create a solvent sheath around ions?
By the water binding to cations through the oxygen adn anions through the hydrogens.
Do smaller or larger ions bind more to H2O?
Smaller ions due to their highly charged nature, making them behave as larger species in solution.
What is activity, 𝒜?
`The effective concentration of a species in a solution, accounting for interactions with other ions.
What does activity do?
Effects the “real” concentration of an ion due to solventation, determining the deviation of the species “behavior” from the ideal, making it highly dependent on ionic strength.
Are Equilibrium constants exact?
No, the constants can change since inert ionic species can alter K-values.
Generally as there is an increasing in the ionic strength there will be …
an increased solubility of sparingly soluble salts.
How are the charges of solvated iions attentuated?
By an increase in the solution ionic strength µ.
What is ionic strength, µ?
The measure of the total concentration of ions in solution, where highly charge d ions are weighted more than less charged species.
What is the equation for ionic strength?
µ = (1/2) • ∑i(ci• zi2), where c is concentration and z is charge
When solving for ionic charge what must be watched?
the stoichiometry of the compound
i.e. Na2SO4
What is the first coordination sphere of lithium ions?
~ 4 H2O
What is the first coordination sphere of chloride ions?
~ 6 H2O
What is the first coordination sphere of Cf3+
~ 8 H2O
What is an ionic atmosphere?
A spherical cloud of charge ∂+ or ∂-, surrounds ions in solution. The charge of the atmosphere is less than the charge of the central atom. The greater the ionic strength of the solution, the greater the charge i each ionic cloud.
What does ionic strength effect?
Structures of intrinsic disordered proteins
activity of enzymes
protein aggregation
protein binding to nucleic acids
etc.
What are the effects of solubility due to ionic strength?
Generally, an increasing ionic strength promotes dissociation into ions, however if the ions are in the reaction they will have the opposite effect and if the compound is not charged there will be no effect.
What is the effect of Activity vs µ?
At zero ionic strength, 𝛾 = 1. The greater the charge of the ions, the more rapidly 𝛾 decreases as ionic strength increases.
What is the point in a titration when the added amount of standard reagent is equal to the around of analyte being titrated?
equivalence point
What is it when the analyte is titrated with the standard reagent and the volume of standard solution required to complete the reaction is measured called?
direct titration
What is a reagent that is pure and stable, which can be used directly after weighing?
primary standard
What is the analyte that is being analyzed in the titration called?
The titrand
What is a stand reagent being added in excess to ensure complete reaction with the analyte. The excess reagent is then titrated with a second standard reagent called?
Back titration
What is a solution, whose concentration is known, often made from a reagent of known purity?
Standard solution.
What is the standard reagent of known concentration that is added from a buret to the analyte solution called?
Titrant
What is it when the analyte does not react directly with the titrant so it is converted to another form which will react with the titrant
indirect titration
What is the point in a titration when a change in the analyte solution is observed indicating equivalency.
End point
What is added to the analyte solution and aids in the observation of the completion of the reaction?
The indicator.
What is the extended Debye-Hückel Equation?
A mathematical expression used to calculate the activity coefficients of ions in solution, particularly at higher concentrations.
When does the Debye Hückel equaqtion work well?
At µ ≤ 0.1 M
What is ⍺?
The theorhetical diameter of a hydrate ions.
i.e. Li+ > Na+ > K+ > Rb+
What ions result in a larger ⍺ value?
Small highly charged ions bind more solvent, more tightly leading to larger values
As µ increase, Ɣ ______.
decreases
As 𝜡 increase, the departure of Ɣ from unity becomes _____ (_____ effective charge)
greater; less
As ⍺ decreases, activity effects become ______ important.
more
What does ⍺ mean?
Diameter of hydrated ion
What does ɣ mean?
The activity coefficient
What does 𝚭 mean?
The charge of the ion
What does µ mean?
the ionic strength
What role do non ionic compounds play in activity?
Since the compounds are neutral there is no change.
Once µ reaches an extremely high point, the ɣ of the compound goes _____?
back up
How do we interpret values in the activity coefficient table if the value of ionic strength of the solution is between table values?
We interpolate between the two closest table values to estimate the activity coefficient.
