Analytical Chemistry Chapter 5 Flashcards
The position of most solution equilibria depends on the ______ of the medium, even when the added electrolyte contains no ion in common with those involved in the equilibrium.
electrolyte concentration
If an electrolyte, such as ______ is added to this solution, the color of the triiodide ion becomes less intense. This decrease in color intensity indicates that the concentration of I3 has decreased and that the equilibrium has been shifted to the left by the added electrolyte.
🍉barium nitrate
🍉potassium sulfate
🍉sodium perchlorate
_____ is a plot of the product of the molar hydronium and hydroxide ion concentration (X 10^4) as a function of the concentration of sodium chloride.
This concentration-based ion product is designated ___.
At low sodium chloride concentrations, K becomes independent of the electrolyte concentration and is equal to ______, which is the _______ constant for water, Kw.
A relationship that approaches a constant value as some variable (here, the electrolyte concentration) approaches zero is called a ______; the constant numerical value observed at this limit is referred to as a _______.
Curve A
Kw
1.00 X 10^14
thermodynamic ion-product
limiting law
limiting value
The vertical axis for ____ in Figure 5-1 is the product of the molar concentrations of barium and sulfate ions (X 10^10) in saturated solutions of barium sulfate. This concentration-based solubility product is designated as ____.
At low electrolyte concentrations, K’sp has a limiting value of _______, which is the accepted thermodynamic value of Ksp for barium sulfate.
curve B
Ksp
1.1x10^10
_____ is a plot of _____ the concentration quotient for the equilibrium involving the dissociation of acetic acid as a function of electrolyte concentra- tion.
Here again, the ordinate function approaches a limiting value _____, which is the thermodynamic acid dissociation constant for acetic acid.
Curve C
K’a (x10^5)
Ka
_____ is a plot of _____ the concentration quotient for the equilibrium involving the dissociation of acetic acid as a function of electrolyte concentra- tion.
Here again, the ordinate function approaches a limiting value _____, which is the thermodynamic acid dissociation constant for acetic acid.
Curve C
K’a (x10^5)
Ka
The _______ in Figure 5-1 represent the ideal behavior of the solutes.
dashed lines
______ are often indicated by adding a prime mark.
Examples are:
As the electrolyte concentration becomes very small, concentration-based equilibrium tion constants approach their thermodynamic values: Kw, Ksp, Ka.
Concentration-based equilibrium constants
🍇K’w
🍈K’sp
🍊K’a
The magnitude of the electrolyte effect is highly dependent on the ____ of the participants in an equilibrium.
When only neutral species are involved, the position of equilibrium is essentially independent of ______.
With _____, the magnitude of the electrolyte effect increases with charge.
charge
Electrolyte concentration
Ionic participants
Systematic studies have shown that the effect of added electrolyte on equilibria is ______ of the chemical nature of the electrolyte but depends on a property of the solution called the _______.
independent
ionic strength
Results from the electrostatic attractive repulsive forces that exist ‘between the ions of an electrolyte and the ions involved in an equilibrium. These forces cause. each ion from the dissociated reactant to be surrounded by a sheath of solution that contains a slight excess of electrolyte ions of opposite charge.
electrolyte effect
Chemists use the term ___, to account for the effects of electrolytes on chemical equilibria.
The activity, or effective concentration, of species X depends on the ionic strength of the medium and is defined as:
ax - Yx[X’]
where ____ is the activity of X,
[X] is its _______, and
yx is a dimensionless quantity called the ________.
activity (a)
ax
molar concentration
activity coefficient
The _____ is more useful than concentration in medical diagnosis since it reflects the body’s conditious.
It’s also the measuring unit by potentiometry but none other instrumental methods.
value of activity
The _______ is a measure of the effectiveness with which that species influences an equilibrium in which it is a participant.
In very dilute solutions, where the ionic strength is minimal, this effectiveness becomes constant, and the activity coefficient becomes unity.
Under such circumstances, the activity and the molar concentration are identical (as are therodynamic and concentra- tion equilibrium constants).
T OR F。As the ionic strength “decreases”, however, an ion loses some of its effectiveness, and its activity coefficient decreases.
activity coefficient of a species
Increases
In solutions that are not too concentrated, the activity coefficient for a given species is independent of the nature of the ______ and dependent only on the ________.
- For a given ionic strength, the activity coefficient of an ion _______ from unity as the charge carried by the species increases. This effect is shown in Figure 5-2. The activity coefficient of an uncharged molecule is approximately unity, regardless of ionic strength.
At any given ionic strength, the activity coefficients of ions of the same charge are approximately _______. The small variations that do exist can be correlated with the effective diameter of the hydrated ions.
The ______ of a given ion describes its effective behavior in all equilibria in which it participates.
electrolyte
ionic strength
departs farther
equal
activity coefficient