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Exam 2 - Flashcards

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Class:CHM 230 - Chemistry 2
Subject:Chemistry
University:Kansas State University
Term:Spring 2010
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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
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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
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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
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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
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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
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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 ]
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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
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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
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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
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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.
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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)))
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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
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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
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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 )
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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
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Kw Kw = (Ka) x (Kb)
Kb (([BH+][OH-]))/[B]
Ka (([H30+][A-]))/[HA]
How do Polyprotic Acids ionize how? In a series of steps
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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
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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
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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
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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
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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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 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 stepsTrue
 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
 Oxacidsacids 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 acidsincreases in acidic solution
 the solubilities of salts of strong acids and strong basesare 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=Ksptrue
 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 pointthe 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 passedFalse, 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 baseTrue, @ 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 addedFalse, 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 4.74the pH will be 4.74, because this is the Half-Equivalence point. @ the Half-Equivalence point pH = pKa
 Q > Kspsupersaturated 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=KspSolution 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 Indicatora 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 moleculesComplex Ions
 How does Complex ion formation affect solubility?complex ions increase solubility of a slightly soluble salt
 KfFormation Constant for complex ions
stability of a complex ion is indicated by Kf magnitude
 AutoionizationAutoionization 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
 KwKw = (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 onthe acid and the base from which the salt was formed
 Predict the pH of NaClNaOH: Strong

HCl: Strong

Solution is NUETRAL
 Predict the pH of CH3CO2NaNaOH: Strong

CH3CO2H: Weak

Solution is BASIC
 Predict the pH of CH3CO2NH4NH4OH: 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 contactFalse, Salts of strong acids and bases DO NOT hydrolyze
 SALT HYDROLYSISreaction of the anion or of the cation, or of both with water
 THE ANION WILL HYDROLYZE IFif... the salt forms from a weak acid and a strong base and the solution will be BASIC
 The cation will hydrolyze ifthe 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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