+0
Karma
Class: | CHM 230 - Chemistry 2 |
Subject: | Chemistry |
University: | Kansas State University |
Term: | Spring 2010 |
How is acid strength related to "Ka" ?
|
The Larger the Ka, The stronger the acid. |
How is acid strength related to molecular structure?
|
*The More (-) the electron affinity, the stronger the acid *The more easily the Halogen - Hydrogen bond is broken the stronger the acid |
Which is the stronger acid, H2S04 or H2S03?
|
H2SO4 |
In benzoic acid, C6H5CO2H, stronger or weaker than acetic acid?
|
Stronger |
Which Base is stronger, NH3 or CH3CO2?
|
NH3 |
True or False:
Polyprotic acids ionize in a series of steps
|
True |
The concentration of the anion is equal to what?
|
the LAST Ka |
When a salt is dissolved in water, the resulting solution can be acidic, basic, or neutral. The pH of the solution depends on what?
|
The acid and the base from which the salt formed |
If the salt is formed from a ----- and a ------, neither the cation nor the anion reacts with water and the solution will be neutral.
|
strong acid (like HCl) and a strong base (NaOH) |
If the salt is formed from a strong acid (HCl) and a weak base (NH3), the cation will react with water and do what?
|
Hydrolyze, forming H3O+ ions and the solution will be acidic |
If the salt is formed from a strong base (NaOH) and a weak acid (CH3CO2H), the anion will react with water and do what?
|
Hydrolyze, forming OH- ions and the solution will be basic |
Oxacids
|
acids that contain H+, O2- and a nonmetal ion that occupies a central position in the molecule e.g. HCl02, H2S04, H3P04, H2C03 |
If the oxidation number of the central atom differs,
|
acid strength increases with increasing oxidation number of the central atom |
What two "ingredients" are in a buffer solution?
|
a weak acid/base and its salt |
how would you choose an acid to prepare a buffer of a specific pH?
|
Choose an acid whose pKa is close to the desired pH |
a common ion (decreases/increases) solubility.
|
a common ion decreases solubility |
AgCl (s) <=> Ag+ + Cl- ..........................................
If NaCl is added to the above equilibrium....
|
Cl-, the common ion, shifts the equilibrium to the left forming more AgCl, decreasing the solubility of AgCl |
Mg(OH)2 (s) <=> Mg2+ + 2OH-
---------------------------
In a basic solution, the common ion, OH-,,,,,,
|
shifts the equilibrium to the left, and decreases the solubility of Mg(OH)2 |
The Solubility of slightly soluble hydroxides and salts of weak acids
|
increases in acidic solution |
the solubilities of salts of strong acids and strong bases
|
are unaffected by pH |
True or false:
In order for a precipitate to form, the ion product, Q, must equal or exceed the Ksp. Q>or=Ksp
|
true |
What are the six strong acids?
|
HCl, HBr, HI, HNO3, HCl04, H2S04 |
What are the strong bases?
|
Group I hydroxides and Ba(OH)2 |
In a Strong Acid - Strong Base, Initially:
|
the pH of the acid is the -log[ of the ACID ] |
In a Strong Acid - Strong Base, As base is added, the pH rises, to determine the pH:
|
the concentration of the excess acid, mol of acid/total volume, must be found. pH= -log[H30+] |
In a Strong Acid - Strong Base, At the equivalence point
|
the pH is 7.00. Only salt and water are present. |
In a Strong Acid - Strong Base, If excess base is added, the pH rises sharply. To determine the pH:
|
the concentration of the excess base, mol of excess base/total volume, must be found. pOH= -log[Base] |
In a Weak Acid - Strong Base, Initially,
|
solve for the concentration of H30+ from the Ka and find pH |
In a Weak Acid - Strong Base, As base is added, the pH rises, to find pH:
|
before the equivalence point, because the salt and acid are present, the solution is a buffer. Find concentration of acid and salt, and use the Henderson-Hasselbalch equation and find the pH. |
In a Weak Acid - Strong Base, At the half equivalence point,
|
concentration of the acid and salt are the same, pH = pKa |
In a Weak Acid - Strong Base, at the equivalence point, all acids have been converted to salt.
|
the pH will be greater than 7 due to the hydrolysis of the anion of the weak acid. Find the concentration of the salt, which is the concentration of the anion. Determine [OH-], then pOH and pH |
In a Weak Acid - Strong Base, If excess base is added,
|
the solution is again a buffer with salt and excess base present. Find the concentration of the salt and the base to use the Henderson-Hasselbalch to determine the pH |
The pH of a buffer solution can be calculated by:
|
the use of the Henderson-Hasselbach equation. pH = pKa + log [conjugate base]/[acid], and pKa = -log|Ka| |
Buffers resist change in pH when?
|
when small amounts of acid or base are added |
is H2CO3/NaHCO3 a buffer system?
|
Yes a weak acid and its salt |
True/False:
In the titration of a weak acid with a strong base, the solution is a buffer after the equivalence point is passed
|
False, the solution is a buffer before the equivalence point is reached |
True/False:
In the titration of a weak acid with a strong base, the pH equals the pKa when half of the acid has reacted with the base
|
True, @ the half equivalence point pH = pKa |
True/False:
The pH of a buffer solution does not change when a small amount of acid or base is added
|
False, The pH will change slightly when a small amount of either is added |
H2S04/NaHSO4. . . Buffer System Solution?
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No No No, H2SO4, Sulfuric Acid, is a strong acid |
H2S/KHS. . . Buffer System Solution?
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Yes Yes Yes, H2S, Hydrogen sulfide, Is a WEAK acid that is with its salt. |
HClO2/NaClO2. . . Buffer System Solution?
|
Yes Yes YES, HClO2 is a weak acid with its salt |
HCl04/NaCl04. . . Buffer System Solution?
|
No No No, HClO4, Perchloric Acid, is one of the strongest acids |
30.0 mL of 0.150 M CH3COOH are titrated with 15.0 mL of .150 M NaOH:
What is the pH? the pKa is 4.74
|
the pH will be 4.74, because this is the Half-Equivalence point. @ the Half-Equivalence point pH = pKa |
Q > Ksp
|
supersaturated solution, Precipitate WILL FORM until the solution becomes saturated. (((Hint: think of the rxn quotient, Q, as the precipitates effort to become alive))) |
Q |
the solution is unsaturated, Precipitate DOES NOT FORM! (((Hint: think of the rxn quotient, Q, as the precipitates effort to become alive))) |
Q=Ksp
|
Solution is saturated, precipitate just BEGINS TO FORM. (((Hint: think of the rxn quotient, Q, as the precipitates effort to become alive))) |
Which of these are Lewis Acids?
Fe3+ , BF3 , H2O , NH3 , NO2- , Cr3+
|
Fe3+ , BF3 , Cr3+ |
What is 0.235 M HBr when diluted TenFold?
|
0.0235 M HBr |
When will two equivalence points be observed?
|
In the titration curve of a diprotic acid, such as oxalic acid, H2C2O4. |
At the equivalence point of the titration curve of a diprotic acid why is the pH acidic when the initial pH was so High?
|
the solution is acidic due to the hydrolysis of the H3O+ |
An Indicator
|
a weak acid or base that changes color at the equivalence point in a titration |
(HInd) In an acid equilibrium lies to the left and the color is green. In base, the equilibrium lies right, the color is purple. [HInd]=[Ind-], [HInd]<[Ind-], [HInd]>[Ind-]?
|
[HInd]=[Ind-], mix of two colors [HInd]>[Ind-], the color is green [HInd]<[Ind-], the color is purple |
When will an indicator change color with respect to a titration curve?
|
in the vertical region |
Molar solubilty = ? .....
Solubility = ? .....
|
Molar solubility (M) = number of moles of solute/liter of solution Solubility = number of grams of solute/volume of solution = g/100ml = g/L |
A small Ksp indicates -------
|
low solubility, but comparisons of the solubility of salts on the basis of their Ksp values can be made only for salts that have the same cation - to - anion ration. |
The Ksp can be compared to help determine what?
|
the solubility of salts that have the same cation - anion ration. e.g. ( Ag2S & PbCl2 ) or ( Ca(OH)2 & MgF2 ) |
ions in which a central metal ion is surrounded by two or more ions or molecules
|
Complex Ions |
How does Complex ion formation affect solubility?
|
complex ions increase solubility of a slightly soluble salt |
Kf
|
Formation Constant for complex ions stability of a complex ion is indicated by Kf magnitude |
Autoionization
|
Autoionization is a process by which atoms or molecules spontaneously transition from an electrically neutral state to a lower-energy ionized state. Water is a very Weak Electrolyte |
Kw
|
Kw = (Ka) x (Kb) |
Kb
|
(([BH+][OH-]))/[B] |
Ka
|
(([H30+][A-]))/[HA] |
How do Polyprotic Acids ionize how?
|
In a series of steps |
The pH of a polyprotic acid is calculated from:
|
The first Ka Most Hydroxide ions come from the first ionization |
The concentration of the anion =
|
The last Ka |
The pH of the solution depends on
|
the acid and the base from which the salt was formed |
Predict the pH of NaCl
|
NaOH: Strong HCl: Strong Solution is NUETRAL |
Predict the pH of CH3CO2Na
|
NaOH: Strong CH3CO2H: Weak Solution is BASIC |
Predict the pH of CH3CO2NH4
|
NH4OH: Weak CH3CO2H: Weak Solution is NUETRAL |
If [HA] > 100Ka
|
(x) is not significant and can be "dropped"
ex.
[HA]>100Ka
[H3O+][A-]/[HA - x] <<<< |
True or False:
Salts of strong acids and bases hydrolyze on contact
|
False, Salts of strong acids and bases DO NOT hydrolyze |
SALT HYDROLYSIS
|
reaction of the anion or of the cation, or of both with water |
THE ANION WILL HYDROLYZE IF
|
if... the salt forms from a weak acid and a strong base and the solution will be BASIC |
The cation will hydrolyze if
|
the salt forms from a strong acid and a weak base and the solution will be ACIDIC |
Both the anion and the cation will hydrolyze if. . .
|
. . . if the salt forms from a weak acid and a weak base. the pH of the resulting solution depends on the relative strength of the acid and the base |
When a question asks for the pH, but gives you the salt of a weak base with its Kb, to find pH: ?
|
First find the Ka by means of the equation Ka = Kw/Kb Second solve for [H3O+] Third Calculate the pH ( -log[H3O+] ) |
Which base is the strongest?
BrO3- , BrO2 - , BrO-
|
BrO- , Less Oxygens Stronger the base |
How does the amount of oxygen in an anion affect the stability?
|
The more oxygen present, the more stable the anion becomes |
Is Water (H2O) a Lewis Acid or Base?
|
A lewis Base |
What is the effect of a common ion on the ionization of a weak acid or a weak base?
|
The common ion REPRESSES the IONIZATION |
Front |
Back |
|
---|---|---|
How is acid strength related to "Ka" ? | The Larger the Ka, The stronger the acid. | |
How is acid strength related to molecular structure? | *The More (-) the electron affinity, the stronger the acid *The more easily the Halogen - Hydrogen bond is broken the stronger the acid | |
Which is the stronger acid, H2S04 or H2S03? | H2SO4 | |
In benzoic acid, C6H5CO2H, stronger or weaker than acetic acid? | Stronger | |
Which Base is stronger, NH3 or CH3CO2? | NH3 | |
True or False: Polyprotic acids ionize in a series of steps | True | |
The concentration of the anion is equal to what? | the LAST Ka | |
When a salt is dissolved in water, the resulting solution can be acidic, basic, or neutral. The pH of the solution depends on what? | The acid and the base from which the salt formed | |
If the salt is formed from a ----- and a ------, neither the cation nor the anion reacts with water and the solution will be neutral. | strong acid (like HCl) and a strong base (NaOH) | |
If the salt is formed from a strong acid (HCl) and a weak base (NH3), the cation will react with water and do what? | Hydrolyze, forming H3O+ ions and the solution will be acidic | |
If the salt is formed from a strong base (NaOH) and a weak acid (CH3CO2H), the anion will react with water and do what? | Hydrolyze, forming OH- ions and the solution will be basic | |
Oxacids | acids that contain H+, O2- and a nonmetal ion that occupies a central position in the molecule e.g. HCl02, H2S04, H3P04, H2C03 | |
If the oxidation number of the central atom differs, | acid strength increases with increasing oxidation number of the central atom | |
What two "ingredients" are in a buffer solution? | a weak acid/base and its salt | |
how would you choose an acid to prepare a buffer of a specific pH? | Choose an acid whose pKa is close to the desired pH | |
a common ion (decreases/increases) solubility. | a common ion decreases solubility | |
AgCl (s) <=> Ag+ + Cl- .......................................... If NaCl is added to the above equilibrium.... | Cl-, the common ion, shifts the equilibrium to the left forming more AgCl, decreasing the solubility of AgCl | |
Mg(OH)2 (s) <=> Mg2+ + 2OH- --------------------------- In a basic solution, the common ion, OH-,,,,,, | shifts the equilibrium to the left, and decreases the solubility of Mg(OH)2 | |
The Solubility of slightly soluble hydroxides and salts of weak acids | increases in acidic solution | |
the solubilities of salts of strong acids and strong bases | are unaffected by pH | |
True or false: In order for a precipitate to form, the ion product, Q, must equal or exceed the Ksp. Q>or=Ksp | true | |
What are the six strong acids? | HCl, HBr, HI, HNO3, HCl04, H2S04 | |
What are the strong bases? | Group I hydroxides and Ba(OH)2 | |
In a Strong Acid - Strong Base, Initially: | the pH of the acid is the -log[ of the ACID ] | |
In a Strong Acid - Strong Base, As base is added, the pH rises, to determine the pH: | the concentration of the excess acid, mol of acid/total volume, must be found. pH= -log[H30+] | |
In a Strong Acid - Strong Base, At the equivalence point | the pH is 7.00. Only salt and water are present. | |
In a Strong Acid - Strong Base, If excess base is added, the pH rises sharply. To determine the pH: | the concentration of the excess base, mol of excess base/total volume, must be found. pOH= -log[Base] | |
In a Weak Acid - Strong Base, Initially, | solve for the concentration of H30+ from the Ka and find pH | |
In a Weak Acid - Strong Base, As base is added, the pH rises, to find pH: | before the equivalence point, because the salt and acid are present, the solution is a buffer. Find concentration of acid and salt, and use the Henderson-Hasselbalch equation and find the pH. | |
In a Weak Acid - Strong Base, At the half equivalence point, | concentration of the acid and salt are the same, pH = pKa | |
In a Weak Acid - Strong Base, at the equivalence point, all acids have been converted to salt. | the pH will be greater than 7 due to the hydrolysis of the anion of the weak acid. Find the concentration of the salt, which is the concentration of the anion. Determine [OH-], then pOH and pH | |
In a Weak Acid - Strong Base, If excess base is added, | the solution is again a buffer with salt and excess base present. Find the concentration of the salt and the base to use the Henderson-Hasselbalch to determine the pH | |
The pH of a buffer solution can be calculated by: | the use of the Henderson-Hasselbach equation. pH = pKa + log [conjugate base]/[acid], and pKa = -log|Ka| | |
Buffers resist change in pH when? | when small amounts of acid or base are added | |
is H2CO3/NaHCO3 a buffer system? | Yes a weak acid and its salt | |
True/False: In the titration of a weak acid with a strong base, the solution is a buffer after the equivalence point is passed | False, the solution is a buffer before the equivalence point is reached | |
True/False: In the titration of a weak acid with a strong base, the pH equals the pKa when half of the acid has reacted with the base | True, @ the half equivalence point pH = pKa | |
True/False: The pH of a buffer solution does not change when a small amount of acid or base is added | False, The pH will change slightly when a small amount of either is added | |
H2S04/NaHSO4. . . Buffer System Solution? | No No No, H2SO4, Sulfuric Acid, is a strong acid | |
H2S/KHS. . . Buffer System Solution? | Yes Yes Yes, H2S, Hydrogen sulfide, Is a WEAK acid that is with its salt. | |
HClO2/NaClO2. . . Buffer System Solution? | Yes Yes YES, HClO2 is a weak acid with its salt | |
HCl04/NaCl04. . . Buffer System Solution? | No No No, HClO4, Perchloric Acid, is one of the strongest acids | |
30.0 mL of 0.150 M CH3COOH are titrated with 15.0 mL of .150 M NaOH: What is the pH? the pKa is 4.74 | the pH will be 4.74, because this is the Half-Equivalence point. @ the Half-Equivalence point pH = pKa | |
Q > Ksp | supersaturated solution, Precipitate WILL FORM until the solution becomes saturated. (((Hint: think of the rxn quotient, Q, as the precipitates effort to become alive))) | |
Qthe solution is unsaturated, Precipitate DOES NOT FORM! (((Hint: think of the rxn quotient, Q, as the precipitates effort to become alive))) | | |
Q=Ksp | Solution is saturated, precipitate just BEGINS TO FORM. (((Hint: think of the rxn quotient, Q, as the precipitates effort to become alive))) | |
Which of these are Lewis Acids? Fe3+ , BF3 , H2O , NH3 , NO2- , Cr3+ | Fe3+ , BF3 , Cr3+ | |
What is 0.235 M HBr when diluted TenFold? | 0.0235 M HBr | |
When will two equivalence points be observed? | In the titration curve of a diprotic acid, such as oxalic acid, H2C2O4. | |
At the equivalence point of the titration curve of a diprotic acid why is the pH acidic when the initial pH was so High? | the solution is acidic due to the hydrolysis of the H3O+ | |
An Indicator | a weak acid or base that changes color at the equivalence point in a titration | |
(HInd) In an acid equilibrium lies to the left and the color is green. In base, the equilibrium lies right, the color is purple. [HInd]=[Ind-], [HInd]<[Ind-], [HInd]>[Ind-]? | [HInd]=[Ind-], mix of two colors [HInd]>[Ind-], the color is green [HInd]<[Ind-], the color is purple | |
When will an indicator change color with respect to a titration curve? | in the vertical region | |
Molar solubilty = ? ..... Solubility = ? ..... | Molar solubility (M) = number of moles of solute/liter of solution Solubility = number of grams of solute/volume of solution = g/100ml = g/L | |
A small Ksp indicates ------- | low solubility, but comparisons of the solubility of salts on the basis of their Ksp values can be made only for salts that have the same cation - to - anion ration. | |
The Ksp can be compared to help determine what? | the solubility of salts that have the same cation - anion ration. e.g. ( Ag2S & PbCl2 ) or ( Ca(OH)2 & MgF2 ) | |
ions in which a central metal ion is surrounded by two or more ions or molecules | Complex Ions | |
How does Complex ion formation affect solubility? | complex ions increase solubility of a slightly soluble salt | |
Kf | Formation Constant for complex ions stability of a complex ion is indicated by Kf magnitude | |
Autoionization | Autoionization is a process by which atoms or molecules spontaneously transition from an electrically neutral state to a lower-energy ionized state. Water is a very Weak Electrolyte | |
Kw | Kw = (Ka) x (Kb) | |
Kb | (([BH+][OH-]))/[B] | |
Ka | (([H30+][A-]))/[HA] | |
How do Polyprotic Acids ionize how? | In a series of steps | |
The pH of a polyprotic acid is calculated from: | The first Ka Most Hydroxide ions come from the first ionization | |
The concentration of the anion = | The last Ka | |
The pH of the solution depends on | the acid and the base from which the salt was formed | |
Predict the pH of NaCl | NaOH: Strong HCl: Strong Solution is NUETRAL | |
Predict the pH of CH3CO2Na | NaOH: Strong CH3CO2H: Weak Solution is BASIC | |
Predict the pH of CH3CO2NH4 | NH4OH: Weak CH3CO2H: Weak Solution is NUETRAL | |
If [HA] > 100Ka | (x) is not significant and can be "dropped" ex. [HA]>100Ka [H3O+][A-]/[HA - x] <<<< | |
True or False: Salts of strong acids and bases hydrolyze on contact | False, Salts of strong acids and bases DO NOT hydrolyze | |
SALT HYDROLYSIS | reaction of the anion or of the cation, or of both with water | |
THE ANION WILL HYDROLYZE IF | if... the salt forms from a weak acid and a strong base and the solution will be BASIC | |
The cation will hydrolyze if | the salt forms from a strong acid and a weak base and the solution will be ACIDIC | |
Both the anion and the cation will hydrolyze if. . . | . . . if the salt forms from a weak acid and a weak base. the pH of the resulting solution depends on the relative strength of the acid and the base | |
When a question asks for the pH, but gives you the salt of a weak base with its Kb, to find pH: ? | First find the Ka by means of the equation Ka = Kw/Kb Second solve for [H3O+] Third Calculate the pH ( -log[H3O+] ) | |
Which base is the strongest? BrO3- , BrO2 - , BrO- | BrO- , Less Oxygens Stronger the base | |
How does the amount of oxygen in an anion affect the stability? | The more oxygen present, the more stable the anion becomes | |
Is Water (H2O) a Lewis Acid or Base? | A lewis Base | |
What is the effect of a common ion on the ionization of a weak acid or a weak base? | The common ion REPRESSES the IONIZATION |
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