Problems 1. Simulated Vinegar One way to make vinegar (not the In a typical anal

Question

Problems 1. Simulated Vinegar One way to make vinegar (not the In a typical analysis, 15 mL of an aqueous solution contain preferred way) is to prepare a solution of acetic acid, the sole ing an unknown amount of acetylcholine had a pH of 7.65 acid component of vinegar, at the proper pH (see Fig. 2-15) incubated with acetylcholinesterase, the pH of the so- and add appropriate flavoring agents. Acetic acid (M, 60) is i decreased to 6.87. Assuming that there was no buffer a liquid at 25, with a density of 1.049 g/m. Calculate the volume that must be added to distilled water to make 1 L of simulated vinegar (see Fig. 2-16). in the assay mixture, determine the number of moles of acetylcholine in the 15 mL sample. 4·Osmotic Balance in a Marine Frog The crab-eating frog of Southeast Asia, Raa cancrivora, develops and ma tures in fresh water but searches for its food in coastal man- grove swamps (corr|posed of 80% to full-strength seawater). When the frog moves from its freshwater home to seawater it experiences a large change in the osmolarity of its envi 2. Acidity of Gastrie HCI In a hospital laboratory a 10.0 ml sample of gastric juice, obtained several hours after a meal, was titrated with 0.1 M NaOH to neutral- ity: 7.2 ml of NaOH was required. The patient's tained no ingested food or drink, thus assume that no buffers were present. What was the pH of the gastric juice? ronment (from hypotonic to hypertonic. (a) Eighty percent seawater contains 460 mM NaCL 10 mM KC, 10 mM CaCh, and 50 mM MgCl What are the con- centrations of the various ionic species in this seawater? As suming that these salts account for nearly all the solutes in 3. Measurement of Acetylcholine Levels by pll Changes The concentration of acetylcholine (a neuro- transmitter) in a sample can be determined from the pH changes that accompany its hydrolysis. When the sample is incubated with the enzyme acetylcholinesterase, acetyl- choline is quantitatively converted into choline and acetic acid, which dissociates to yield acetate and a hydrogen ion: seawater, calculate the osmolarity of the seawater (b) The chart below lists the cytoplasmic concentrations of ions in R. cancrivora. Ignoring dissolved proteins, amino acids, nucleic acids, and other small metabolites, calculate the osmolarity of the frog's cells based solely on the ioniccon centrations given below CH K+ Ca2+ Mg2+ Na+ (mM) (mM)(mM((mu) CH R cancrivora 122 10 100 Acetylcholine CH, (c) Like all frogs, the crab-eating frog can exchange gases through its permeable skin, allowing it to stay under water for long periols of time without breathing. How does the high permeability of frog skin affect the frog's cells when it moves from fresh water to seawater? CHs Choline Acetate

Explanation / Answer

Ans. Given, Initial pH = 7.65

            Final pH = 6.87

            Reaction volume = 15.0 mL = 0.015 L

# Initial [H3O+] = 10-pH = 10-7.65 = 2.23872 x 10-8 M

# Final [H3O+] = 10-6.87 = 1.34896 x 10-7 M

# Increase in [H3O+] = Final [H3O+] – Initial [H3O+]

                                    = 1.34896 x 10-7 M - 2.23872 x 10-8 M

                                    = 1.1251 x 10-7 M

# According to the stoichiometry of balanced reaction, 1 mol acetylcholine yields 1 mol H3O+. So, increase in [H3O+] must be equal to the concentration of acetylcholine in the reaction mixture which was hydrolysed to produce [H3O+].

So,

            [Acetylcholine] in reaction mixture = 1.1251 x 10-7 M

Now,

            Moles of acetylcholine = Molarity x Volume of reaction mixture in liters

                                                = 1.1251 x 10-7 M x 0.015 L

                                                = 1.6876 x 10-9 mol

# Therefore, moles of acetylcholine in assay mixture = 1.6876 x 10-9 mol

Related Questions

Navigate

• Browse (All)
• Browse P
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.