Analysis and Calculations The experiment is a strong acid-strong base titration. From this experiment, we can analyze concentration of base when the concentration of acid is known. The HCl solution, added with a few drops of phenolphthalein, is placed into the Erlenmeyer flask and the NaOH solution is slowly added from the burette into the HCl solution in small drops. Neutralization occurred in the titration process: NaOH (aq) + HCl (aq) → NaCl (aq) + H2O (l) This reaction shows that 1 mol of NaOH will react with 1 mol of HCl to produce 1 mol of the salt (NaCl) and 1 mol of water. Phenolphthalein indicator is used to determine the end-point of the titrated solution.
Write this down when you start the titration. Next, you must determine the volume of the solution delivered to reach the equivalence point. Next, you will find the moles of base used in the titration: *Note that the volume of base is in L, not in mL Determine number of moles of HCl in flask: If you write the balanced reaction for the neutralization of sodium hydroxide and hydrochloric acid, you will see that the reaction proceeds in a 1:1 fashion. That is, for every hydroxide (OH‐) ion added, it can neutralize exactly one hydronium (H+) ion. This is not always the case for neutralization reactions, and is thus not always the case for acid‐base titrations.
The following is a copy of the calculations done using decimals: 5.The equivalence point of the titration curve measured in step 1 was 25.25 mL of NaOH. Half of this value is 12.63 mL. By interpolating the graph, the pH at this volume was 4.80, which is equivalent to the pKa of acetic acid. According to the tabulated data, the pKa was 4.90 at 15 mL of NaOH. At this point, the change in pH with respect to volume was minimal since these values were far from the equivalence point, which occurred experimentally at 27.41 mL.
The volumetric flask was then filled up to its 100 mL mark with deionized water. The buret was washed out with dionized water and then with the strong base NaOH before being filled up with NaOH. About 20 mL of the unknown weak acid was pipetted into a beaker. The starting volume of the NaOH in the buret was recorded before about 4 mL of the strong base was titrated into the weak acid solution. The final volume was recorded.
If this happens, the mixture boils and it would be necessary to start the experiment all over again. After obtaining an homogeneous mixture, the flask was placed in an ice bath during five minutes next to a graduated cylinder containing 5.0 mL of concentrated sulfuric acid. The temperature of the ice bath was recorded to be 1.1 °C. Likewise, a second graduated cylinder containing 1.8 mL of nitric acid and 2.5 mL of sulfuric acid was immersed in the cold ice bath to keep the three different solutions at the same temperature. Thereafter, the cold 5.0 mL of H2SO4 were added to the erlenmeyer flask containing the acetanilide solution, which remained in the cold water for approximately another 4 minutes.
After adding small amounts of NaOH portions at a time until reaching the pH value of 11.5, the points recorded lead to the determination of the half equivalence point of the pH and the pKa . The half equivalence point of the volume NaOH can be identified by dividing the highest
The acid was poured into the flask until there was a permanent pink colour. The acid was allowed to be poured for a little longer before the flask was removed and taken to a lab bench with a buret that contained 0.1 M sodium hydroxide, and the amount of acid used was recorded. The sodium hydroxide was added into the flask in small amounts
This has to be prepared fresh. Procedure : (a) Preparation of calibration curve :(i) Pippet portions of standard NiSO4 solution into 100 ml volumetric flask. Use a series from 50 to 250 µg Ni. (ii) Add 25 ml 1.0 N HCl in 5 ml bromine water. (iii) Cool with cold running tap water and add 10 ml concentrated Ammonium hydroxide.
THEORY OF THE EXPERIMENT In this experiment change in the volume of reagents by diluting with water is used as change in the concentration and reciprocal of the time taken for the appearance of blue black colour as the reaction rate. Equation of reaction H2O2 (aq) + 2H+ (aq) +2I- (aq) I2 + 2H2O Hypothesis Hypothesis 1: Decrease in concentration of hydrogen peroxide (H2O2) decreases the rate of reaction (that is, increases the time for reaction to come to completion). In the reaction between potassium iodide (KI), hydrogen peroxide, Sodium thiosulfate (Na2S2O4) under acidic condition. Hypothesis 2: Decrease in the concentration of potassium iodide decreases the rate of reaction (that is increases the time for the reaction to come to completion). In the reaction between potassium iodide (KI), hydrogen peroxide, sodium thiosulfate (Na2S2O3) under acidic condition.