Question

Pre-lab Questions for Experiment #8 (Experiment-20 in our lab manual) Titration of Acids and Bases 1) Fill in the blanks in the following figure that represents the setup of today's experiment N Y (6) (1)------- - (2) ---------- (3)---------- -------------- (4)---------- 17 (8) _----- --------------- (5) --------- TO --------------- 2) What is the purpose of using phenolphthalein for an acid-base titration? 3) What is the color of phenolphthalein indicator in: a) Acidic solution: _;b) Basic solution: 4) A 40.0 mL sample of 0.100 M HCl is titrated with 0.100 M NaOH. Calculate the pH after the addition of each of the following volumes of NaOH: (a) 0.0 mL, (b) 10.0 mL, (c) 20.0 mL, (d) 40.0 mL, (e) 60.0 mL. A plot of the pH of the solution as a function of the volume of added titrant is known as a pH titration curve. Using the available data points, plot the pH titration curve for the above titration.

Answer 1

1). Fill in the blanks - 1- Burette 6- Meniscus 2- Ring stand 7- Standardized solution 3- Clamp 4- stop cock 8- Sample to be titrated 5- Erlenmeyer flask g- Acid / Base Indicator 2). What is the purpose of using phenolphthaleen for au acid-base titration ? Answer: The equivalence point for titrations between strong bases and weak acids occurs some where upward of pH 7, depending on the aced and the base Phenolphthalein changes colour between a pH of roughly around 8-10, which fits nicely within the range of the equivalence point of these titration making them useful 3). What is the colour of phenolphthalein indicator in:- - as Acidic solution : - Colourless b). Basic solution: Pink