Unit 3: Solubility and Kinetics Flashcards
Solubility
The maximum amount of solute that can be dissolved in a solvent at equilibrium
Unsaturated solution
When the solute concentration is less than its equilibrium solubility concentration
Saturated solution
When a solute concentration is equal to its equilibrium solubility concentration
ex. flat coke
Supersaturated solution
When a solute concentration is greater than its equilibrium solubility concentration
Precipitation Reactions general formula
AB(aq) + CD (aq) <=> AD(aq) + CB(s)
A double-replacement reaction is where ____________ react to form ____________.
dissolved substances, one (or more) solid products
The solid that is formed in a double-replacement reaction is known as a ___________.
precipitate
The solution above the precipitate is called the __________.
supernatant
The equation in which all ionic species (regardless of their physical state) are kept in their formula units, is called a ______________ or __________________.
molecular equation, formula unit equation
Total ionic equations
include all ions and compounds in the reaction in the form they actually exist in the solution
Net ionic equations
only include the ions forming a precipitate, and neglect to include ions remaining dissolved in solution (spectators)
Ions that are in the same form on both the reactant side and product side of the equation are canceled
Always soluble:
Li+ Na+ K+ Rb+ Cs+ NH4+ NO3– ClO3– ClO4– CH3COO–
Never soluble (except soluble when bonded with Group 1 elements and NH4+):
phosphate: PO43–
carbonate: CO32–
sulfite: SO32–
Usually insoluble (except soluble when bonded with Group 1 elements and and NH4+ and some Group 2 elements):
OH– S2–
When in doubt,
__________ compounds are usually insoluble.
Ag, Hg, and Pb
Before a solution is saturated, a solid will _____________ dissolve. Once saturation is reached, the rate of dissolution of the solid and the rate of reforming the solid from dissolved ions are _____________ and the system is ___________
spontaneously, equal, at equilibrium
Compounds that we call insoluble are those whose lowest free energy point for the dissolving process lies …
very close to 100% solid reactant(s) and nearly 0% ionic products.
The ____________ is the equilibrium constant for the equilibrium between a slightly soluble ionic solid and a solution of its ions when the reaction is written as the solid dissolving into ions.
solubility product constant (Ksp)
Since there is always only one solid reactant in a solubility chemical equation, there is never a __________ in a Ksp expression.
denominator
When Qsp > Ksp, the reaction shifts to the ___________
reactants (to the left).
For solubility reactions, the solid is the reactant on the left. Thus, if Qsp > Ksp, the compound will precipitate.
When Qsp < Ksp, the reaction shifts to the ____________
products (to the right).
For solubility reactions, the dissolved ions are the products on the right. Thus, if Qsp < Ksp, the ions remain dissolved.
When Qsp = Ksp, the reaction is at _____________.
equilibrium
molar solubility (x)
the number of moles per liter of the compound that will dissolve in a saturated solution
just AB dissolving in water
Ksp equation?
Ksp = x^2
just A2B or AB2 dissolving in water
Ksp equation?
Ksp = 4x^3
just A3B or AB3 dissolving in water
Ksp equation?
Ksp = 27x^4
just A2B3 or A3B2 dissolving in water
Ksp equation?
Ksp = 108x^5
[ion] =
(x) (subscript)
x =
[ion] / subscript
to get grams per liter…
multiply moles/L x molar mass = g/L
to get molar solubility from g/L…
divide g/L by molar mass = mol/L
Ksp values for 3:2 or 2:3 ratios are ________
very small
the common ion effect occurs in a solution in which…
the same ion is provided by two different compounds.
will concentration of Mg2+ be greater if MgF2 is dissolved in pure water or in a solution of 0.1M sodium fluoride?
pure water
what is the molar solubility (x) of MgF2 in water?
Ksp = 4x^3
x = (Ksp/4)^1/3
what is the molar solubility (x) of MgF2 in 0.10 M NaF?
Ksp = [Mg2+] [F-]^2
solve for [Mg2+]
what is the molar solubility (x) of MgF2 in 0.10 M MgNO3?
Ksp = [Mg2+] [F-]^2
solve for [F-]
divide by 2 bc x = [ion] / subscript
Thermodynamics tells us about the _________ of a chemical reaction, whereas kinetics tells us about the __________ of the reaction.
energy, rate
If you calculate the reaction rate at t = 0, what rate did you just calculate?
instantaneous rate and initial rate
Any factors that causes molecules to __________________ speeds up the reaction rate
collide more frequently
The factors affecting the rates of a chemical reaction
Medium or Nature of the Reactants
Concentration (pressures for gases)
Temperature
A catalyst
For a reaction that is zero-order overall the rate…
does not change during the reaction.
Rate will also not change for a ___________ if you double or triple the concentration of reactant.
zero-order reaction
A catalyst…
speeds up the reaction by lowering activation energy but does not change K (equilibrium constant)
All else being equal, a reaction with a higher activation energy compared to one with a lower activation energy will…
proceed slower.
If the exponents in the rate-law do not match the coefficients in the balanced chemical equation, then we know that…
the reaction does not take place in one step.
Transition states are _______________.
short-lived
where is the reaction rate the fastest?
at the beginning
Reaction Rate
CH3Cl + OH- –> CH3OH + Cl-
rate = ?
-∆ [CH3Cl] /∆t = ∆ [CH3OH] /∆t
Reaction Rate:
the change in concentration of one of the reactants of products at a selected stage of the reaction divided by the time interval over which change takes place
___________ is the reaction rate at a specific moment in time or specific concentration
Instantaneous
___________ is the reaction rate over a defined time interval
Average
___________ is a single unique average rate of reaction that is uniform across all reactants and products
Unique average reaction rate
The instantaneous rate is the ___________ to the curve at the time of interest
slope of the tangent
Most instantaneous rates ___________ as the reaction proceeds.
decrease
The instantaneous rate of reaction at the start of the reaction is called the ____________
initial rate of reaction