Interpretation:
The
Concept introduction:
Titrations are recorded with a help of various titration curves, in which the volume of the titrant (known solution) is taken as an independent variable and the
To determine: The
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Chemistry: An Atoms First Approach
- The titration curves for two acids with the same base are shown on this graph. (a) Which is the curve for the weaker acid? Explain your choice. (b) Give the approximate pH at the equivalence point for the titration of each acid. (c) Explain why the pH at the equivalence point differs for each acid. (d) Explain why the starting pH values of the two acids differ. (e) Which indicator or indicators, phenolphthalein, bromthymol blue, or methyl red, could be used for the titration of Acid 1? For the titration of Acid 2? Explain your choices.arrow_forwardConsider the nanoscale-level representations for Question 110 of the titration of the aqueous weak acid HX with aqueous NaOH, the titrant. Water molecules and Na+ ions are omitted for clarity. Which diagram corresponds to the situation: After a very small volume of titrant has been added to the initial HX solution? When enough titrant has been added to take the solution just past the equivalence point? Halfway to the equivalence point? At the equivalence point? Nanoscale representations for Question 110.arrow_forwardYou have a 16 mL sample of acetylcholine (a neurotransmitter) with an unknown concentration and a pH of 7.66. You incubate this sample with the enzyme acetylcholinesterase to convert all of the acetylcholine to choline and acetic acid. The acetic acid dissociates to yield acetate and hydrogen ions. At the end of the incubation period, you measure the pH again and find that it has decreased to 5.52. Assuming there was no buffer in the assay mixture, determine the number of nanomoles of acetylcholine in the original 16 mL sample. Acetylcholine CH₂ acetycholine in original sample: CH,—C−O−CH,—CH,AN-CH, HO–CH,—CH,*N–CH, + CHy H₂O I CH3 CH3 Choline CH₂ CH,-GO + H Acetate nmolarrow_forward
- You have a 20 mL sample of acetylcholine (a neurotransmitter) with an unknown concentration and a pH of 8.17. You incubate this sample with the enzyme acetylcholinesterase to convert all of the acetylcholine to choline and acetic acid. The acetic acid dissociates to yield acetate and hydrogen ions. At the end of the incubation period, you measure the pH again and find that it has decreased to 6.70. Assuming there was no buffer in the assay mixture, determine the number of nanomoles of acetylcholine in the original 20 mL sample. -Å-—•- CH,—C−O−CH,—CH,—*N–CH, Acetylcholine CH₂ acetycholine in original sample: CH₂ H₂O CH₂ I HO–CH,—CH,—*N–CH, + CH Choline CH₂ CHO Acetate H* nmolarrow_forwardYou have a 18 mL sample of acetylcholine (a neurotransmitter) with an unknown concentration and a pH of 7.82. You incubate this sample with the enzyme acetylcholinesterase to convert all of the acetylcholine to choline and acetic acid. The acetic acid dissociates to yield acetate and hydrogen ions. At the end of the incubation period, you measure the pH again and find that it has decreased to 5.66. Assuming there was no buffer in the assay mixture, determine the number of nanomoles of acetylcholine in the original 18 mL sample. Tip: your answer should have two significant digits! Only the mantissa (the digits to the right of the decimal) are significant when you raise a decimal number to a power. CH,—C−O−CH,—CH,—*N—CH, Acetylcholine CH 3 acetycholine in original sample: CH3 H₂O CH3 HO–CH,—CH,—*N–CH, + CH, Choline CH3 CH, T Acetate O + H+ nmolarrow_forwardDraw the titration curves for the titrations of (a) a strong acid with a strong base, (b) a strong acid with a weak base, (c) a weak acid with a strong base and (d) a weak acid with a weak base. Make sure you label each of them properly (volume on x-axis and pH on the y-axis). Describe how you would determine the Ka for a weak acid from the titration curves.arrow_forward
- You have a 12 mL sample of acetylcholine (a neurotransmitter) with an unknown concentration and a pH of 8.14. You incubate this sample with the enzyme acetylcholinesterase to convert all of the acetylcholine to choline and acetic acid. The acetic acid dissociates to yield acetate and hydrogen ions. At the end of the incubation period, you measure the pH again and find that it has decreased to 6.55. Assuming there was no buffer in the assay mixture, determine the number of nanomoles of acetylcholine in the original 12 mL sample. Acetycholine in original sample:________ nmolarrow_forwardYou have a 11 mL sample of acetylcholine (a neurotransmitter) with an unknown concentration and a pH of 8.22. You incubate this sample with the enzyme acetylcholinesterase to convert all of the acetylcholine to choline and acetic acid. The acetic acid dissociates to yield acetate and hydrogen ions. At the end of the incubation period, you measure the pH again and find that it has decreased to 6.62. Assuming there was no buffer in the assay mixture, determine the number of nanomoles of acetylcholine in the original 11 mL sample. CH,—C−O−CH,—CH,—*N-CH, Acetylcholine CH3 acetycholine in original sample: I CH₂ H₂O CH₂ HO–CH,—CH,—*N–CH, + CH,-C−O + H* CH₂-8-0 Choline | CH3 Acetate nmolarrow_forwardA buffer is made using 100.0 mL of 0.100 M CH3 CH2 COOH (propanoic acid) and 100.0 mL of 0.100 M NACH3 CH2 COO (sodium propanoate). A) Explain in your own words what will occur (at the molecular level) when an nitric acid is added to the buffer? What would be the effect on the pH? B) Explain in your own words what will occur when LIOH is added tot he buffer? What would be the effect on the [H+]?arrow_forward
- Equal quantities of 0.010M solutions of an acid HA and a base B are mixed. The pH of the resulting solution is 9.4 Part A:Write the equilibrium equation for the reaction between HA and B. Express your answer as a chemical equation. Identify all of the phases in your answer. Part B: Write equilibrium-constant expression for the reaction between HA and B. Part C: If Ka for HA is 8.0×10−5, what is the value of the equilibrium constant for the reaction between HA and B? Express your answer using one significant figure. Part D: What is the value of Kb for B? Express your answer using one significant figure.arrow_forwardIn a laboratory experiment, a student has 1 L of solution containing a weak base at a concentration of 0.300 M. In order to create a buffer, a strong acid is added, which converts some of the base in the solution to its conjugate weak acid to create a buffer. If the student wants to create the most effective buffer that can be equally resistant to both acids and bases how many moles of strong acid should the student add to the buffer? (Please provide your answer to 3 decimal places.)arrow_forwardA buffer is made using 100.0 mL of 0.100 M CH;CH,COOH (propanoic acid) and 100.0 mL of 0.100 M NaCH;CH,COO (sodium propanoate). A) Explain in your own words what will occur (at the molecular level) when an nitric acid is added to the buffer? What would be the effect on the pH? B) Explain in your own words what will occur when LIOH is added tot he buffer? What would be the effect on the [H+]?arrow_forward
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