Determination of pKa and pKb Using Acid-Base Titrations Lab Report
Objectives:
This experiment aims at determining the concentration of acid-base equilibrium constants for acetic acid and aqueous ammonia using titration curves.
Introduction:
The main objective in the volumetric titration of an acid with a base is the determination of the equivalence point. The equivalence point is a point where the acid has been fully neutralized by the base. One can determine the completeness of the reaction by adding an indicator that changes when the reaction is approaching an equivalence point. Furthermore, the completeness of a reaction can be determined by a pH meter. A pH meter measures the actual pH of the solution during titration. pH titration
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A graduated cylinder was used to add 10ml of distilled water into a 100ml volumetric flask. 5.0ml concentrated acetic acid was pipetted into a 100ml volumetric which already had 10ml of distilled water. After adding acetic acid, the volumetric swirled to thoroughly mix the solution. The volumetric flask was then topped to the mark with distilled water and covered.
(2) Titration of Acetic Acid with Sodium Hydroxide
10ml of distilled water was added into a 250ml Erlenmeyer flask. 20ml of diluted acetic acid was then added into it, followed by setting up a titration system with 0.100M of NaOH in buret. A pH meter was used to monitor the pH of the solution as the base (NaOH) was added. Sodium hydroxide was added in an increment of 1ml until the solution pH reached 4.8. After the solution pH reached, the base was added in an increment of 0.2ml until the equivalence point was passed. After the equivalence point, the base was added in an internal of 1ml until there was an insignificant change in the solution pH. The volume of the base and pH of the solution were recorded and used to draw a titration
1mL of Acetic acid was then added to Unknown D and the solution was stirred. Next, 15mL of sodium
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.
Weighed 1 gram of NaC2H3O2 and mixed it with ionized water. Boiled 12 mL of 1.0M Acetic Acid added into a beaker containing the sodium carbonate on a hot plate until all the liquid is evaporated
Standard Sodium hydroxide solution is the alkaline solution that will be used to titrate with soda water as it is a common solution that can be easily found in an ordinary school laboratory. It is a strong base. Carbonic acid is a weak acid which will react with a strong base to form a basic (pH > 7) solution. When Phenolphthalein is added to Soda water, the resultant solution is colourless. After titration with a strong base (sodium hydroxide), the solution will turn to pink as the solution becomes
CLAIRE MUNTING 29/01/2018 Criterion C EFFECTS OF SURFACE AREA OF CALCIUM CARBONATE UPON RATE OF REACTION Calcium Carbonate Chips 1 Introduction: Within the current investigation, the effects of the surface area of Calcium Carbonate (CaCO3) in combination with Hydrochloric acid (HCl) upon its rate of reaction. CaCO3, commonly referred to as limestone, is an organic substance and is, in a sense, the crystallised “carbonic salt” of the element, calcium2. In addition to being a salt, the pH level of Calcium Carbonate is 9.91, and it is therefore, a basic substance, due to the fact that it is comprised of a pH level higher than 7, which is neutral3. HCl, however, is the bodily acid found in the stomach of human beings.
Commercial vinegar, Yamaha brand 0.1 mol/dm3, NaOH soloution Phenolpthalein indicator soloution (50.00 ± 0.5 cm3 ) cm3 burrete (250.00 ± 0.5 cm3) volumetric flask a (250 cm3± 0.5 cm3)
IV. Data and observations Mass of beaker (g) 174.01 Mass of beaker + NaOH pellets (g) 174.54 Mass of NaOH pellets 0.53 TRIAL 1 TRIAL 2 Mass of potassium acid phtalate (KHP) (g) 0.15 0.15 final buret reading (ml) 30.75
Practical I: Acid-base equilibrium & pH of solutions Aims/Objectives: 1. To determine the pH range where the indicator changes colour. 2. To identify the suitable indicators for different titrations. 3.
The mixture were stirred by using a glass rod until the mixture is fully dissolved. The solution were tested by using calibrated pH meter to get the pH value of the solution. Results and Discussions pH ratio between acid and base: 7.3 = 6.82 + x x = 0.48 0.48 = log ([base])/([acid]) 100.48 =base/acid salt/acid = 3.02 There, 1 acid : 3 base calculate number of mole of acid and base to find the mass : molar = mol/L 50 mM = (mol )/(0.5 L) mol = 25 mol number of mole of NaH2PO4 25/4 = acid = 6.25 mol number of mole of Na2HPO4 25/4 × 3 = salt = 18.75 mol to calculate the mass of the acid and base : Mass of NaH2PO4 (6.25 mol)/(119.98 g/mol)=0.052g
Buffer solutions of pH 4 and 7 6. Graduated cylinder - 100 mL 7. Volumetric flask with stopper - 250 mL 8. Two 100-mL beakers 9. Two 50-mL Burettes 10.
In direct titrations, the number of moles of acid can be easily derived by simply manipulating with the values of acid and base given in the experiment. In back titration, excessive volumes of acid are always added. Of which, only a certain quantity would be neutralised. The number of moles of acid is eventually derived from titrating this excess acid with a strong base and using mole fractions to calculate. The quantity of acid neutralised is obtained by subtracting the moles of acid given at the start of the experiment, with the moles of acid titrated.
Introduction The goal of the experiment is to examine how the rate of reaction between Hydrochloric acid and Sodium thiosulphate is affected by altering the concentrations. The concentration of Sodium thiosulfate will be altered by adding deionised water and decreasing the amount of Sodium thiosulphate. Once the Sodium thiosulphate has been tested several times. The effect of concentration on the rate of reaction can be examined in this experiment.
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. This can also be seen on the graph as the plateau before the inflection point occured. To calculate the Ka of the acid, the following formula is
That caused a new initial reading of NaOH on the burette (see Table1 & 2). The drops were caused because the burette was not tightened enough at the bottom to avoid it from being hard to release the basic solution for titrating the acid. The volume of the acid used for each titration was 25ml. The volume of the solution was then calculated by subtracting the initial volume from the final volume. We then calculated the average volume at each temperature.
II. METHODOLOGY In order to perform this experiment, the students will need a distillation set-up with a connector receiver, an iron ring and stand, a Bunsen burner, a wire gauze, a 250mL round bottom flask, a graduated cylinder, a thermometer, one or two boiling chips, an alcoholic beverage, masking tape, an ice bath, a stirring rod, and, optionally, food coloring. It is imporatnt to avoid playing with the apparatus and equipment so as to avoid breakage and injuries, especially since fire is being dealt with in this experiment.