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Which factor does NOT affect the ionization constant of boric acid complexes?
Which factor does NOT affect the ionization constant of boric acid complexes?
What effect does glyoxal have on boric acid according to the content?
What effect does glyoxal have on boric acid according to the content?
What does the ionization constant, K**, depend on?
What does the ionization constant, K**, depend on?
What is the reported conductivity increment for a solution containing glyoxal and boric acid?
What is the reported conductivity increment for a solution containing glyoxal and boric acid?
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Which method is NOT used to determine the ionization constant?
Which method is NOT used to determine the ionization constant?
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What is the association constant of glyoxal with borate ion as mentioned in the content?
What is the association constant of glyoxal with borate ion as mentioned in the content?
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What happens to the conductivity after mixing boric acid and glyoxal?
What happens to the conductivity after mixing boric acid and glyoxal?
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What is suggested about the reaction preference of glyoxal regarding boric acid and borate ion?
What is suggested about the reaction preference of glyoxal regarding boric acid and borate ion?
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What does the equation provided for ionization constants include?
What does the equation provided for ionization constants include?
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Which of the following factors was unexpectedly affected by the presence of borax in aqueous glyoxal solutions?
Which of the following factors was unexpectedly affected by the presence of borax in aqueous glyoxal solutions?
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Which polyol shows the highest conductivity enhancement?
Which polyol shows the highest conductivity enhancement?
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What role do electron donating groups have on the carbon holding the OH groups in terms of conductivity enhancement?
What role do electron donating groups have on the carbon holding the OH groups in terms of conductivity enhancement?
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Which hydroxy acid has the highest conductivity enhancement value?
Which hydroxy acid has the highest conductivity enhancement value?
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Among the following, which factor is noted to enhance conductivity?
Among the following, which factor is noted to enhance conductivity?
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What is the conductivity enhancement value for glycerol?
What is the conductivity enhancement value for glycerol?
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Which of the following polyols has a conductivity enhancement value closest to 500?
Which of the following polyols has a conductivity enhancement value closest to 500?
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What is the conductivity enhancement value of cis-1,2-cyclohexanediol?
What is the conductivity enhancement value of cis-1,2-cyclohexanediol?
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Which element or group is observed to increase conductivity enhancement the most?
Which element or group is observed to increase conductivity enhancement the most?
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What is the association constant, K, obtained in the absence of salt?
What is the association constant, K, obtained in the absence of salt?
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What effect does the presence of salt have on the precision of pH readings?
What effect does the presence of salt have on the precision of pH readings?
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What does the slope of the line obtained from plotting pK** against the negative logarithm of the glyoxal concentration indicate?
What does the slope of the line obtained from plotting pK** against the negative logarithm of the glyoxal concentration indicate?
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What was the value of n obtained from the given experiment?
What was the value of n obtained from the given experiment?
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What correction was applied to the pK** value in the absence of salt?
What correction was applied to the pK** value in the absence of salt?
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What is the significance of diluting the solution with potassium chloride?
What is the significance of diluting the solution with potassium chloride?
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Which method is indicated for determining the dissociation constant in the absence of salt?
Which method is indicated for determining the dissociation constant in the absence of salt?
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In the experiment described, what is the primary variable measured in relation to the pH?
In the experiment described, what is the primary variable measured in relation to the pH?
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What was the method used to determine the ionization constants of boric acid?
What was the method used to determine the ionization constants of boric acid?
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Which factor interferes with the buffer capacity method for boric acid?
Which factor interferes with the buffer capacity method for boric acid?
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What happens to the dissociation constant of boric acid when salts like KCl are added?
What happens to the dissociation constant of boric acid when salts like KCl are added?
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What value of pK for boric acid ionization was obtained through the experiments?
What value of pK for boric acid ionization was obtained through the experiments?
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What is the significance of thermodynamic equilibrium constants in the context provided?
What is the significance of thermodynamic equilibrium constants in the context provided?
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What conductivity value was measured for 0.5M boric acid before purification?
What conductivity value was measured for 0.5M boric acid before purification?
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What role did phenolphthalein play in boric acid analysis?
What role did phenolphthalein play in boric acid analysis?
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What effect does standing time have on the conductivity of the boric acid-glyoxal solution?
What effect does standing time have on the conductivity of the boric acid-glyoxal solution?
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What was the primary reason for the negative conductivity increment observed with glutaraldehyde and a-hydroxyadipaldehyde?
What was the primary reason for the negative conductivity increment observed with glutaraldehyde and a-hydroxyadipaldehyde?
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Which aldehyde has a greater affinity for cellulose compared to glutaraldehyde and a-hydroxyadipaldehyde?
Which aldehyde has a greater affinity for cellulose compared to glutaraldehyde and a-hydroxyadipaldehyde?
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What method was used to determine ionization constants in the study?
What method was used to determine ionization constants in the study?
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Which factor decreases the contribution of boric acid to the conductivity in the mixture?
Which factor decreases the contribution of boric acid to the conductivity in the mixture?
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What did the method of Kili’ primarily minimize during the determination of ionization constants?
What did the method of Kili’ primarily minimize during the determination of ionization constants?
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In the given equation for calculating minimum buffer capacity, what does K l * represent?
In the given equation for calculating minimum buffer capacity, what does K l * represent?
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What does a plot of incremental change in pH versus the increment of acid or base added illustrate?
What does a plot of incremental change in pH versus the increment of acid or base added illustrate?
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Which concentration of boric acid was used in the experiment for determining ionization constants?
Which concentration of boric acid was used in the experiment for determining ionization constants?
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Study Notes
Reaction of Glyoxal with Boric Acid and Borate Ion
- Glyoxal promotes the ionization of boric acid, likely by withdrawing borate ions from solution.
- The association constant between glyoxal and borate ion is 2.8 x 105.
- Conductivity in glyoxal and boric acid solutions is unusually high (1032 µ-mhos).
- This supports the polycyclic structure of aqueous glyoxal.
- Glyoxal-borate salts were not isolated.
- Different methods for determining ionization "constants" yielded different results, potentially due to glyoxal's preference for reacting with borate ions over boric acid.
- "Constants" corresponded to molar ratios of glyoxal to borate ion of 3-2 and 2-7 at 25°C.
- The latter ratio likely represents the average degree of glyoxal polymerization in solution.
Discussion
- Glyoxal, known to exist in hydrated form, primarily reacts as a dialdehyde.
- The discovery that borax increases the acidity of aqueous glyoxal solutions was unexpected.
- Increased acidity in boric acid solutions often results from reactions with bidentate ligands (e.g., polyhydric alcohols, phenols, hydroxy acids, and dibasic acids).
- This often involves a coordination reaction with the conjugate base of boric acid, B(OH)4- in water.
- In the glyoxal-boric acid system, the cis configuration and planar OC-CO conformation of glyoxal enhance boric acid acidity.
- Electron donating and withdrawing groups on the carbons holding hydroxyl groups affect the conductivity enhancement.
- Increased functionality and acidity also contribute to greater conductivity enhancement.
Determination of Conductivity Increment
- Glyoxal's increase in boric acid solution conductivity stems from complex formation.
- Conductivity initially increases, but then decreases after about 6 hours due likely to polymerization changes in glyoxal during dilution.
- When a stock solution of 5.73M glyoxal is mixed with a stock solution of boric acid at 25°C to 0.500M, the conductivity increment is 1642 µ-mhos initially, but decreases to 1032 µ-mhos after 64 hours.
Determination of "Ionization Constants"
- Ionization constants aren't constant because the ratio of components changes with concentration, altering the ionizing species.
- This is further complicated by glyoxal's slow depolymerisation.
- Ionization constants often follow a formula, K** = CK1K2 + K1, where K1 is the association constant between boric acid and glycol, and K1 is the first ionization constant of boric acid.
- Ionization constants were measured using the buffer capacity method and the half-neutralization method.
- Conductivity-based methods weren't reliable for measuring these constants due to the complexes forming with glyoxal.
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Description
Explore the fascinating reaction between glyoxal and boric acid, highlighting the ionization of boric acid and the unusual conductivity levels in their solutions. This quiz delves into aspects such as the association constant between glyoxal and borate ions, ionic behavior, and polycyclic structures in aqueous solutions.