conj basw
Titration Curve of a Weak Acid-Strong Base Titration
-Initial pH is around 3, not 1 -Shorter vertical region around the eq. point -Eq. point above 7
Titration Curve of a Strong Acid-Weak Base Titration
-Starts with only weak base in solution -Initial pH is around 11 -Equivalence point is below 7
A cation that will not affect the pH of a solution...
1. A Group 1A or heavy Group 2A cation (except Be²⁺)
Two factors that influence acid strength (ionization)
1. H−X bond STRENGTH -The stronger the H-X bond, the less likely the acid will break up (ionize), the weaker the acid -Strong H-X bond=Weak acid 2. H−X bond POLARITY -The more polar the H-X bond, the more likely it will break up (ionize), the stronger the acid -The more polar the H-X bond, the stronger the acid
An anion that will make a solution basic is...
1. The conjugate base of a weak acid (F⁻ of HF)
A cation that will make a solution acidic is...
1. The strong conjugate acid of a weak base (NH₄⁺) 2. A small, highly charged metal ion (Al³⁺, Cr³⁺, Fe³⁺, Bi³⁺)
An anion that will not affect the pH of a solution...
1. The weak conjugate base of a strong acid (Cl⁻ of HCl, NO₃⁻ of HNO₃)
Buffer
A solution that contains a weak acid and its conjugate base; it resists changes in pH upon additions of small amounts of acid or base. The conjugate base must be provided by a dissolved salt.
Relationship between an acid/base and its conjugate.
A strong acid yields a weak conjugate base. A strong base yields a weak conjugate acid. A weak acid yields a strong conjugate base. A weak base yields a strong conjugate acid.
Difference between a strong Br∅nstead acid and a strong conjugate acid
A strong conjugate acid acts only as a weak Bronstead acid in water; and a strong conjugate base acts only as a weak Bronstead base in water. Strong conjugates react with water, but only t a small extent. Weak conjugates do not react with water to any measurable extent.
Lewis Acid
A substance that can accept an electron pair. Metal ions such as Al³⁺ are always lewis acids
Lewis Base
A substance that can donate an electron pair.
Determining strength of Hydrohalic acids
Acid strength increases as the H-X bond strength decreases
Carboxylic Acids
Acids that contain an "R" atom bonded to a carboxyl group, -COOH.
Oxoacids
Acids that contain hydrogen, oxygen and a central, nonmetal atom. Contain more than one O-H bond.
Why does a strong acid ionize completely?
Because its conjugate base has almost no affinity for the H₃O⁺ ion in solution.
Hydrohalic Acids
Binary acids formed from halogens. (HF, HCl, HBr, HI) HF is the only weak acid of the hydrohalic acids
How to qualitatively determine the pH of a salt solution
By identifying the ions in solution and determining which of them, if any, undergoes significant hydrolysis.
Generic Equation for Weak Acid-Strong Base titration
CH₃COOH(aq)+OH⁻(aq)→CH₃COO⁻(aq)+H₂O(l) Then the acetate ion undergoes hydrolysis: CH₃COO⁻(aq)+H₂O(l)↔CH₃COOH(aq)+OH(aq)
Complex Ions
Complex ion formation increases the solubility of a substance.
Generic Equation of a Strong Acid-Strong Base Titration
HCl(aq)+NaOH(aq)→NaCl(aq)+H₂O(aq) OR H₃O⁺(aq)+OH⁻(aq)→H₂O(aq)
Predicting Precipitation Reactions
If Q≤Ksp, no precipitate If Q>Ksp, precipitate forms
Determining strength of Oxoacids
If the central atom is electronegative or is in a high oxidation state, it will attract electrons, causing the O-H bonds around it to be more polar, thus making the acid stronger. The more ELECTRONEGATIVE or the HIGHER the OXIDATION state of the central atom, the stronger the acid.
What makes a strong conjugate base strong?
It has a high affinity for H⁺ ions from water and hydronium.
What measures acid strength?
Its tendency to ionize.
Relationship between the strength of an acid/base and that of its conjugate.
Ka × Kb = Kw As Ka increases, Kb decreases, and vice versa. If the acid is strong, the conjugate base is weak, and vice versa.
Relationship between ionization constant and substance strength.
Large Ka=strong acid Large Kb=strong base
How to find initial pH of a Weak Acid-Strong Base Titration?
Make an ICE chart starting with the initial concentration of weak acid— the ONLY substance in solution at that time
Amphoteric Hydroxides
Metal Hydroxides that can reaction with acids and bases. Ex: Al(OH)₃, Cr(OH)₃, Pb(OH)₂
How pH affects solubility
Salts that contain a basic ion are more soluble in acidic solution than in water. (ex: OH⁻, F⁻) BaF(aq)↔Ba⁺(aq)+F⁻(aq) The H₃O⁺ in the acid consumes the F⁻ F⁻(aq)+H₃O⁺(aq)↔H₂O(l)+HF(aq) Therefore [Ba] in Ksp=[Ba⁺][F⁻] must increase. When Ksp increases, solubility increases.
How to determine the strength of two Oxoacids whose central atoms are the same but are bonded to a different number of oxygen atoms.
The acid whose central atom has the highest oxidation number (the largest number of oxygens attached to its central atom).
How to determine the strength of two Oxoacids whose central atoms are from the same group and have the same oxidation number
The acid whose central atom is more electronegative is stronger, this is because the more electronegativity eaton will attract electrons from O-H bonds more effectively, making the bonds more polar.
What makes weak conjugate base weak?
The base has no affinity for H⁺ ions from water or hydronium; ∴ it stays alone such as Cl⁻. This is also why the acid that created it is strong, because the conjugate base stays alone, maintaining dissociation.
Carboxylate Anion
The conjugate base of a Carboxylic Acid; Lewis structure is resonance.
What happens when an strong acid is added to a buffer
The conjugate base of the solution's weak acid consumes the foreign strong acid, converting it to the weak acid of the solution. This weakening of the new acid minimizes alterations in pH. H₃O⁺(aq)+CH₃COO⁻(aq)→CH₃COOH(aq)+H₂O(l)
Formation Constant, Kf
The equilibrium constant of a complex ion formation. The larger the Kf, the more likely the complex ion will form.
Solubility Product Constant, Ksp
The equilibrium constant of the equilibrium expression of the dissociation of an insoluble compound.
Equivalence Point of a Strong Acid-Strong Base Titration
The equivalence point is where the pH is 7, and equal molar amounts of acid and base have been used.
Trend in acid successive acid ionization constants for diprotic and polyprotic acids
The first ionization constant is much larger than the second, and so on. This is because it is easier to remove a proton from a neutral species than one that is negatively charged, and it is easier to remove a proton from a species with a single charge than from one with a double negative charge.
How to find the pH of a titration AT the equivalence point
The ion from the salt is the only substance in solution. Find its milimolar amount and divided it by total volume of solution to get M. Use M in an ICE chart of the hydrolysis of the ion. Find the concentration of [OH] of [H₃O], then find pH.
Relationship between Ksp and solubility
The larger Ksp, the more soluble the ionic compound
How to determine strength of a Carboxylate Anion
The more spread out or delocalized the electron density of the structure, the stronger the acid. This depends on the nature of the "R" group. The more electronegative "R" is, the more polar the molecule, typically, and the stronger the acid. The more spread out or delocalized the electron density of the structure, the more stable the anion, the more likely to ionize, the stronger the acid.
Solubility
The number of grams of solute in 1 L of a saturated solution (g/L)
Molar Solubility
The number of moles of solute in 1 L of a saturated solution (mol/L)
Salt Hydrolysis
The process in which ions produced from the dissociation of a salt act as weak acids or weak bases and react with water to produce either hydroxide or hydronium ions- thus impacting the pH.
What happens when a strong base is added to a buffer
The weak acid in solution consumes the foreign strong base (OH⁻) and converts it to a weak base (CH₃COO⁻). This weakening of the new base minimizes alterations in pH. OH⁻(aq)+CH₃COOH(aq)→CH₃COO⁻(aq)+H₂O(l)
How to find the pH of a strong acid-strong base titration.
Use concentrations of the acid and base to find the milimolar concentration of both. Mulitply the volume of the liquid added by the milimolar concentration and find the difference of the acid and base in milimoles. Divided this mmol number by the total volume. Using this [H₃O⁺] or [OH⁻], find pH.
How to find pH of a titration before the equivalence point
Use the Henderson-Hasselbalch eq. pH=pKa+log([CB]/[WA])
Acid-Base Indicator
Usually a weak organic acid or base for which the ionized and un-ionized forms are different colors. HIn(aq)+H₂O(l)↔H₃O⁺(aq)+In⁻(aq) The endpoint of a titration is the point at which the color of the indicator changes. Not all indicators change color at the same pH though, so the choice of indicaor for a particular titration depends on the strength of the acid or base used in the titration. We usually pick an indicator that changes color over a pH range that coincides with the steepest part of the titration curve.
Guidelines for qualitatively determinant the pH of a salt solution in which both salt ions hydrolyze
When Kb>Ka, the solution is basic When Kb<Ka, the solution is acidic When Kb≈Ka, the solution is neutral or nearly neutral
The Common Ion Effect
When a compound containing an ion in common with a dissolved substance is added to a solution at equilibrium, the equilibrium shifts to the left and the ionization of the weak electrolyte is suppressed. Ex. The addition of CH₃OONa to a CH₃COOH solution at equilibrium shifts the reaction to the left CH₃COOH(aq)+H₂O(l)↔H₃O⁺(aq)+CH₃OO⁻(aq) ←←←←←←←←←←←←←←←←←←←←←←
The Common Ion Effect' effect on Solubility
When a compound dissolves in an aqueous solution containing one of the ions from the liquid, the substance is less soluble. Ex. When AgCl dissolves in AgNO₃, it is significantly less soluble than it is in water
Basic Salt Solutions
When a strong conjugate base (weak Br∅instead base) of a weak acid reacts with water to produce a hydroxide ion and a weak acid. A⁻(aq)+H₂O(l)→HA(aq)+OH⁻(aq) We can make the prediction that a solution of a salt in which the anion is the conjugate base of a weak acid (F⁻ of HF) will be basic. The pH of the solution is calculated from the Kb value, which is obtained from the Ka × Kb = Kw eq (Ka=ionization constant of weak acid)
Acid Salt Solutions
When the cation of a salt is the strong conjugate acid of a weak base, the solution of the salt will be acidic. The cation reacts with water to produce a conjugate base and hydronium. NH⁺₄(aq)+H₂O(l)→NH₃(aq)+H₃O⁺(aq)
