Passage
Within the renal system, two buffers operate to counter the production of excess H⁺ from luminal H₂CO₃. They are located within the tubular lumen, and maintain urinary pH levels between 4.5 and 8.0.The first of these is a phosphate buffer, which serves as the primary buffer for urine because its pK_a is very close to extracellular fluid pH of 7.4. The phosphate buffer operates according to Reaction 1. H₂PO₄⁻ is excreted in urine.
Reaction 1During acidosis when tubular pH is low, the phosphate buffer system becomes saturated. An ammonia buffer system then becomes the primary buffer, and NH₄⁺ is excreted in urine.
Reaction 2Titratable acid (TA) is the total acid in urine, and it can be found using Folin's method. Under normal physiological conditions, TA is approximately equal to the amount of phosphate in urine, which is a product of serum phosphate concentration and glomerular filtration rate. This makes TA a good indicator of kidney function.Folin's method involves back titration of a urine sample to a pH of 7.4 using a strong base. In a typical procedure, potassium oxalate is added to remove calcium from the sample prior to titration with 1.0 M NaOH. The titration continues until the solution reaches a pH of 7.4 (measured by a pH meter) . The amount of base required for the titration can then be used to calculate the amount of H₂PO₄⁻ in the urine sample.
-If a student adds bromothymol blue as an indicator to determine the amount of titratable acid in 25 mL of urine according to Folin's method, what effect will the bromothymol blue have on the pH of the urine sample?

Question

Passage
Within the renal system, two buffers operate to counter the production of excess H⁺ from luminal H₂CO₃. They are located within the tubular lumen, and maintain urinary pH levels between 4.5 and 8.0.The first of these is a phosphate buffer, which serves as the primary buffer for urine because its pK_a is very close to extracellular fluid pH of 7.4. The phosphate buffer operates according to Reaction 1. H₂PO₄⁻ is excreted in urine.

Passage Within the renal system, two buffers operate to counter the production of excess H<sup>+</sup> from luminal H<sub>2</sub>CO<sub>3</sub>. They are located within the tubular lumen, and maintain urinary pH levels between 4.5 and 8.0.The first of these is a phosphate buffer, which serves as the primary buffer for urine because its pK<sub>a</sub> is very close to extracellular fluid pH of 7.4. The phosphate buffer operates according to Reaction 1. H<sub>2</sub>PO<sub>4</sub><sup>−</sup> is excreted in urine. <strong>Reaction 1</strong>During acidosis when tubular pH is low, the phosphate buffer system becomes saturated. An ammonia buffer system then becomes the primary buffer, and NH<sub>4</sub><sup>+</sup> is excreted in urine. <strong>Reaction 2</strong>Titratable acid (TA) is the total acid in urine, and it can be found using Folin's method. Under normal physiological conditions, TA is approximately equal to the amount of phosphate in urine, which is a product of serum phosphate concentration and glomerular filtration rate. This makes TA a good indicator of kidney function.Folin's method involves back titration of a urine sample to a pH of 7.4 using a strong base. In a typical procedure, potassium oxalate is added to remove calcium from the sample prior to titration with 1.0 M NaOH. The titration continues until the solution reaches a pH of 7.4 (measured by a pH meter) . The amount of base required for the titration can then be used to calculate the amount of H<sub>2</sub>PO<sub>4</sub><sup>−</sup> in the urine sample. -If a student adds bromothymol blue as an indicator to determine the amount of titratable acid in 25 mL of urine according to Folin's method, what effect will the bromothymol blue have on the pH of the urine sample? A) It will increase the pH of the sample. B) It will decrease the pH of the sample. C) It will neutralize the sample. D) It will have no effect on the pH of the sample.

Reaction 1During acidosis when tubular pH is low, the phosphate buffer system becomes saturated. An ammonia buffer system then becomes the primary buffer, and NH₄⁺ is excreted in urine.

Reaction 2Titratable acid (TA) is the total acid in urine, and it can be found using Folin's method. Under normal physiological conditions, TA is approximately equal to the amount of phosphate in urine, which is a product of serum phosphate concentration and glomerular filtration rate. This makes TA a good indicator of kidney function.Folin's method involves back titration of a urine sample to a pH of 7.4 using a strong base. In a typical procedure, potassium oxalate is added to remove calcium from the sample prior to titration with 1.0 M NaOH. The titration continues until the solution reaches a pH of 7.4 (measured by a pH meter) . The amount of base required for the titration can then be used to calculate the amount of H₂PO₄⁻ in the urine sample.
-If a student adds bromothymol blue as an indicator to determine the amount of titratable acid in 25 mL of urine according to Folin's method, what effect will the bromothymol blue have on the pH of the urine sample?

Quizplus · Accepted Answer

11ecba2d_1213_ba70_a3bf_edea0ba104b4_MD0008_00 An indicator is used in acid-base titrations to determine the endpoint of a titration. A good indicator should change color close to the equivalence point of a titration. The equivalence point is the stoichiometric amount of titrant needed to react with all of the solution being titrated. In the case of a buffer solution, a titration is halfway to the equivalence point when a pH is achieved that is near the pK_a value of the buffer's acid. Bromothymol blue is an indicator that changes from pale yellow to dark blue, from pH 6 to 8, but it has no effect on the pH of the solution. (Choices A and B) An indicator does not affect the pH of the system because it does not participate in the reaction. The pH will neither increase nor decrease. (Choice C) An indicator only responds to changes in pH; it does not aid in neutralizing the solution. Educational objective: Indicators are used in acid-base titrations to determine the endpoint of a titration. A good indicator should change color close to the equivalence point, the point at which the stoichiometric amount of titrant needed to consume all of the acid or base in the solution has been added. Indicators do not participate in the reaction.

Passage Within the Renal System, Two Buffers Operate to Counter the the Production