⚫ 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.

A 1.00 liter solution contains 0.60 M ammonia and 0.46 M ammonium iodide.If 0.23 moles of nitric acid are added to this system,indicate whether the following statements are true or false.(Assume that the volume does not change upon the addition of nitric acid.) A. The number of moles of NH3 will decrease.    B. The number of moles of NH4+ will decrease.    C. The equilibrium concentration of H3O+ will remain the same.    D. The pH will decrease.    E. The ratio of [NH3] / [NH4+] will decrease.

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

Consider the buffer system composed of benzoic acid, HC, H,O,, and its conjugate base benzoate, C,H,0;. HC,H,0, + H,0 = H,0* +C,H,0, Using Le Châtelier's principle, predict how the concentration of each substance changes by the addition of H,O*. Does the concentration of HC, H,0, increase or decrease when H,0* is added? O increase decrease Does the concentration of C, H,0, increase or decrease when H,O* is added? O decrease O increase Does the concentration of H,O* change significantly when H,O* is added? O no Does the concentration of H,O* change significantly when H,Ot is added? по yes Does the pH change significantly when H,O is added? no O yes Using Le Châtclier's principle, predict how the concentration of cach substance changes by the addition of OH. Does the concentration of HC,H,O, increase or decrease when OH is added? increase O decrease Does the concentration of C,H,O, increase or decrease when OH" is added? O decrease

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.

A 29.2 mL sample of 0.289 M ammonia, NH3, is titrated with 0.359 M nitric acid. The pH before the addition of any nitric acid is Use the Tables link in the References for any equilibrium constants that are required.

15.0 mL of 0.50 M NaOH is added to a 100.-mL sample of 0.487 M NH3 (Kb for NH3 = 1.8 × 10–5). What is the equilibrium concentration of NH4+ ions? Group of answer choices 1.1 × 10–2 M 7.6 × 10–6 M 4.2 × 10–1 M 1.2 × 10–4 M none of these