9. Measurement of Acetylcholine Levels by pH Changes You have a 15 mL sample of acetylcholine (a neurotransmitter) with an unknown concentration and a pH of 7.65. 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. 010 CH3 H₂O CH3-C-O-CH2-CH2-N-CH3 CH3 Acetylcholine CH3 HO-CH2-CH2-N-CH3 + CH3-C-0¯ + H+ CH3 Choline Acetate At the end of the incubation period, you measure the pH again and find that it has decreased to 6.87. Assuming there was no buffer in the assay mixture, determine the number of nanomoles of acetylcholine in the original 15 mL sample.

The average normal concentration of Ca2+ in urine is 5.33 g/L. Calculate the concentration of oxalate needed to precipitate calcium oxalate to initiate formation of a kidney stone. Ksp of calcium oxalate = 2.3 × 10−9. Calculate the minimum phosphate concentration that would precipitate a calcium phosphate kidney stone. Ksp of calcium phosphate = 2.0 × 10−29.

Based upon the observations of the FeCl3 summarized in the following table, answer the following question. /tr> Sample Tested pH Color with FeCl3 0.15% salicylic acid 4.0 Purple Commercial aspirin brand: 4.8 Pale yellow Buffered aspirin brand: 5.6 Pale yellow Aspirin product 3.1 Pink/light purple What does FeCl3 react with to produce a positive result? Normal BIIU X2| X² | → EE E fx | 田|ミ| || Based upon the observed results, what can you conclude about the purity of your product? Normal BIIIU 三二市_ 中 fx| 的|三|||

MISSED THIS? Read Section 18.8 (Pages 829 - 833). Part A A solution is made that is 1.0x10-3 M in Zn(NO,), and 0.130 Min NH3. After the solution reaches equilibrium, what concentration of Zn?+ (aq) remains? Express your answer using two significant figures. Zn]= 5.1• 10- M Submit Previous Answers Request Answer X Incorrect; Try Again; One attempt remaining

7. A common buffer solution can be prepared by using ammonia and ammonium salts. The base equilibrium constant of ammonia, NH3, is 1.815x10-5 A student worker is asked to prepare a buffer solution with NH3 and ammonium salt. However, after the student did a thorough search, no ammonium salt is found. After the student reported the result to the professor, the professor told the student the buffer can be prepared with ammonia and a strong acid. Can you help this student out? The pH of the buffer to be prepared is 10.08. The molarity of the ammonia in the buffer is 0.4717 M. The molarity of the ammonia solution found in the laboratory is 1.201 M, the strong acid solution is 0.9948 M HNO3. The volume of the buffer solution to be prepared is 500.0 mL. Please answer the following questions. A. B. What is the molarity of the ammonium ion in the buffer? Please provider your answer below. Check answer How many mL of 0.9948 M HNO3 solution is needed? Please provider your answer below. 0² 0₂ $…

Amino acids with the general formula below can behave as buffers(R is some number of CH2 groups) what equation represents the result of buffering the addition of an acid? Explain

Upon adding 0.75 g sulfamic acid to 0.85 M solution of NaNO,, you notice that there is violent bubbling, a release of heat, and the formation of an orange-brown gas. Your lab partner isolates the gas in a stoppered test tube. The equilibrium for the orange-brown gas generated from the experiment is shown below. 2NO2) N20Alg) AHxn <0 (orange-brown) (colorless) What would you observe upon placing the test tube with the colored gas in an ice bath? O The orange-brown color would become even more intense. O The gas would become a brown liquid, and then solidify. O The test tube would become very hot. O The color would gradually fade. It is impossible to tell with the information provided

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:________ nmol

:In the following buffer solution CH3COOH 2 CH3CO0 + H+ CH3COO + H+ CH3COONA СНЗСОО + Na* h reaction occurs when few drops of HCl are added into the buffer CH3COOH becomes active and the reaction turns right .A O CH3COO- becomes active and the reaction turns right .B O CH3COO- becomes active and the reaction turns left.CC CH3COOH becomes active and the reaction turns left .D O

2. Write the equilibrium expression for Ca2+ + 2Cl->