⚫ To 3 mL of 0.10 M HC_H₂O2 add a drop of methyl orange, then add 1 M NaC HO₂ a few 3 2 3 drops at a time, with mixing. Explain your observations in terms of the equilibrium equation and the common ion effect. • Write the equilibrium equation and explain your observations in terms of the equilibrium equation and the common ion effect in your notebook.

You have a solution of the weak acid HA and add some of the salt NaA to it. What are the major species in the solution? What do you need to know to calculate the pH of the solution, and how would you use this information? How does the pH of the solution of just the HA compare with that of the final mixture? Explain.

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A 1.00 liter solution contains 0.59 M nitrous acid and 0.44 M sodium nitrite. If 35.0 mL of water are added to this system, indicate whether the following statements are true or false. (Note the the volume MUST CHANGE upon the addition of water.)   A. The concentration of HNO2 will increase.   B. The concentration of NO2- will decrease.   C. The equilibrium concentration of H3O+ will increase.   D. The pH will decrease.   E. The ratio of [HNO2] / [NO2-] will increase.

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

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 $…

8. Our bodies are able to preserve a near constant pH due to the presence of hydrogen carbonate anion (HCO,). K values for the diprotic acid carbonic acid (H,CO;) are Kaj = 4.5 x 10?, K2 = 4.7 x 10-". a) Hydrogen carbonate anion is an amphoteric species. Define amphoteric. b) In the space below, write out chemical equations to describe the behavior of this species as both a Bronsted acid and a Bronsted base, and use the equilibrium constants given above to decipher whether a solution of HCO;¯ will be acidic, basic, or neutral. Support your answer with pertinent calculations.

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. O CH3 CH3-C-O-CH2-CH2-N–CH3 Acetylcholine CH3 H₂O CH3 HỌCH, CH, N– CH3 + CH3-CHO TH 11 CH3 Choline Acetate T 4 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.

What you expect to observe on mixing 6M NH3 with HCl. Will there be a color? Will bubbles form? Will the solution turn hot? Will a precipitate form and if so, what will its color be?

A solution is prepared that is initially 0.30M in hydrofluoric acid (HF) and 0.13M in potassium fluoride (KF). Complete the reaction table below, so that you could use it to calculate the pH of this solution. Use x to stand for the unknown change in [H3O+]. You can leave out the M symbol for molarity. [HF] [F] [H,O] initial 0 0 change 0 final 0 0 ㅁ 1 G