Titration Pre-Lab Assignment

Titration Pre-Lab Assignment Purpose: Many titrations will be conducted using a strong base of a known concentration to determine the concentration of a solution of hydrochloric acid (HCl). Sodium hydroxide, a strong base, will need to be prepared and its concentration will have to be standardized using potassium hydrogen phthalate (KHP). Then, the standardized NaOh solution will be used to titrate the unknown concentration of the HCl solution at a known volume. The results of the titration wil be used to deduce the concentration of the HCl and the pH will be monitored through a pH probe and the phenolphthalein (pH indicator) during every titration. Objectives: 1. Using a 50 mL burette, a pH probe, and a pH indicator, learn how to correctly perform a titration 2. Learn to create a second derivative plot and determine the equivalence point of all titration with Logger Pro 3.14 3. Determine the concentration of the unknown concentration of the HCl solution through titrating solution with known amounts of KHP 4. Determine the concentration of the unknown concentration of the HCl solution through titrations with the standardized NaOH solution. Compounds : NaOH Unknown HCl solution Deionized H2O KHP phenolphthalein indicator Materials: Vernier LabQuest 400 mL beaker 250 mL beaker 100 mL beaker 50 mL graduated cylinder 5 mL volumetric pipette 50 mL burette 3 prong/utility clamp Vernier pH sensor plastic funnel pipette bulb analytical balance stir plate magnetic stir bar burette clamp Chemical Hazards: Chemical spill of HCl and NaOH may lead to harmful health problems if ingested or inhaled like burning of flesh. Physical Hazards: Broken glassware Equation: 1. HCl (aq) + NaOH (aq) → NaCl (aq) + H2,O (l) 2. KHC8H4O4 (aq) + NaOH (aq) → NaKHC8H4O4 (aq) + H2,O (l) Outline: Part A: preparation and standardization of NaOH 1. 2. 3. 4. Calculate the theoretical amount of NaOH Measure water and pour into beaker Weigh NaOH Add water and mix until NaOH is fully dissolved LabQuest: 1. 2. 3. 4. 5. Plug LabQuest into outlet Plug pH probe into Channel 1 “Sensors” - “Data Collection” Mode: “Events with Entry” Name : “volume” units: “mL” - Condition burette - Close stopcock and add water - Cover open end and inver - Put on ring stand - Repeat until burette has been rinsed 4 times Fill burette with previous NaOH solution - - Prepare KHP solution - Weigh 2 grams of KHP and record mass - Add water to beaker and dissolve - Adjust burette - Prepare pH probe for measurement - “Collect”- “graph view” - To add second data pair add NaOH to KHP - Determine exact amount of NaOH - “Keep” and enter NaOH volume - Proceed with titration - Keep adding NaOH until 3 mL under the theoretical value - When 3 mL under add two 0.5 mL portions of NaOH and record pH - Add final about 1 mL of NaOH and close stopcock when solution turns pink and remains for 5 seconds (endpoint) Endpoint - Add two 0.5 mL portions, three 1 mL portions, and two 2 mL portions of NaOH - “Stop” - - Repeat with KHP Part B: Titration of HCl - Retrieve 15 mL of unknown sample of HCl and record number Refill burette with the same NaOH add phenolphthalein to a beaker with water and unknown sample Perform “fast run” Add NaOH and record final volume Repeat steps for first formal trial of unknown HCl sample “Collect” , 0 for inital volume Add NaOH until 3 mL below endpoint When 3 mL below add smaller amounts of NaOH Add final about 1 mL of NaOH and close stopcock when solution turns pink and remains for 5 seconds (endpoint) Add four 1 mL and two 2 mL portions of NaOH “Stop” Change roles and repeat Unplug probe and turn LabQuest off