Question

Pre-Lab Questions 1. Calculate the theoretical equivalence point (the volume!) in terms of ml NaOH adde each of the titrations. Assume the concentration of acid is 0.81 M and the concentration of base is 0.51 M. 2. Which equation can be used to find the pH of a buffer? Calculate the pH of a buffer containing 0.20 M CH3COOH and 0.20 M CH3COONa. What is the pH after adding 10.0 mL of 0.10 M HCl to 65.0 mL of the buffer? 3. The addition of water will change the pH of an acidic (or basic) solution. Why? 4. The addition of water will not change the endpoint of a titration. Why? Materials Standardized sodium hydroxide (NaOH) Hydrochloric acid (HCI) Acetic acid (HC2H3O2) Sodium acetate (NaC2H302) Commercial vinegar 10 mL vol pipet (stock room) & bulb Magnetic stir bar (stockroom) & stir plate Phenolphthalein Ring stand and buret clamp Small 3-prong clamp 50 mL buret & funnel Erlenmeyer flask LabQuest device pH electrode (stock room)

Please help with the prelab questions! thank you!!!! Especially 2 and 3!

Answer 1

3) Addition of water increases the volume which decreases the concentration of H+ (acidic solution) or OH- (basic solution) ions and therefore pH changes. Because pH is negative log of H+ ion concentration or pOH is negative log of OH- ion concentration.

pH + pOH = 14

2) I have attached image.

. equation Henderson - Hasselbalch pH of buffer. is weed to find the pH = pkat log [CH₂ Coo) [cycoon pH = 4.74 + log 02 = 4.74 loge =) pH = 4.74 е Е (0 - - + и lovou mmoles си, Coo 65x0.2 - 13 13 -1 си, Слън 65x0.2 13 13+1 bH = 4.74 t log 12 0 14 I pH = 4.67