“Comparative pH titrations of strong and weak acids”
Experiment #6 – The aim of the experiment is to titrate a strong acid and a weak acid with a primary standard
solution NaOH and finding its pH. The titrant NaOH which is 1M is filled in the burette. Below
the titrant, a 250-ml beaker is positioned is such a way that while titrating the NaOH is poured
down the beaker which is filled with a solution of 75-ml of DI water and 25-ml of HCL. In order
to begin titration, the electrode is put into the beaker such that it doesn’t hit the spinning stir bar.
A magnetic stir bar is kept underneath the 250-ml beaker so that the mixture gets dissolved
faster. The pH is recorded on the instrument named pH meter which the records the pH
…show more content…
Before equivalence point i.e., between
0% to 90% of the reaction, the pH for HCL increases faster than acetic acid to reach the
equivalence point. At this phase the solution is acidic. At the equivalence i.e., between 90% and
100% of the reaction, the moles of acid are stoichiometrically equal to the moles of base. The
equivalence point for both HCL and acetic acid is 7.67 and 9.19 respectively. The volume at
which the equivalence point occurs is 23.25 ml and 24.50 ml respectively for HCL and acetic
acid. The volume is different because of the different pH. The phase here changes from acidic to
basic and the jumps are sudden for both the acids. Beyond the equivalence point i.e., between
110% and 200% of the reaction, the reaction is almost complete, the base has already reacted
with the acid at this point of the reaction and both HCL and acetic acid has nearly a similar pH
after the equivalence point because at this phase the pH is controlled by the base since it is in a
basic medium. The pH at 0% of the reaction for HCL and acetic acid is 0.70 and 2.72
respectively. At 50% i.e., between the 0% and the equivalence point, the pH for HCL is 3.84
Hydrochloric acid is the clear colourless solutions of hydrogen chloride (HCl) in water, hydrochloric acid is also a highly corrosive substance and a strong mineral acid meaning they are formed from inorganic compounds, hydrochloric acid is a monoprotic acid meaning that it can only ionize one H+ ion. As a result hydrochloric acid can be used in a wide range of industrial practices such as removing rust from steel, ore processing, the production of corn syrup and making of PVC plastics. Hydrochloric acid is made using a very straight forward method which involves dissolving hydrogen chloride (HCl) in water, releasing the H+ cation and Cl- anion. In this aqueous form the H+ ion joins water to form a hydronium ion (H3O+)
and thiosulphate will not be mixed up. The amount of HCl will be 5 cm3
The whole purpose of this experiment is to determine wether or not the amount of the zinc and or hydrochloric acid effects the out coming percent of the solution after under going chemical reaction.
The equivalence point is halfway up the steep curve and for a weak acid- weak base titration, the pH is NOT neutral at the equivalence point, but approximately 8.
2. In the large beaker, put water and boil it completely. After that, remove the beaker from heat. 3. Sample tubes (A-D) should be labeled and capped tightly.
From looking at the results I can conclude that when the pH was 3 and
The temperature at which the reaction is carried out Use of a catalyst Reaction equation is mentioned above but rate equation can only be decided by doing experiments. So, the following procedure can be used to carry out the experiment. Plan Equipment 2 Measuring cylinders Beaker Stopwatch Paper with black cross on it Sodium Thiosulphate (different concentrations) Hydrochloric acid (same concentration each time) Water (different concentrations) Pipette. Prediction I predict that the greater the concentration of sodium thiosulphate solution, the faster the chemical reaction will take place.
The solution was poured into a 250.0cm3 volumetric flask. Deionized water was used to rinse the conical flask so that all the solution was transferred.
tube. Add 6 mL of 0.1M HCl to the first test tube, then 0.1M KMnO4 and
Before the acetic acid solution could be titrated with sodium hydroxide (NaOH), the actual concentration of NaOH needed to be determined. By way of standardization, the actual concentration of NaOH was established, to account for the fact that the solid is not pure and for its tendency to react with carbon dioxide in the air.
In the titration experiment, the endpoint was recorded in the experimental data to be at 21.30 mL of NaOH and at a pH of 10.44. However, when all of the data from the table was graphed, the observed endpoint was too high up and on a part of the upper concave down portion of the graph. To ensure that the proper equivalence point was used, a new point had to be extrapolated that was roughly the point at which the graph went from concave up to concave down. This point was at 21.28 mL of NaOH added and pH of 9.20. Dividing both of these points by two, the half equivalence point was found to be at a pH of 5.30 and 10.64 mL of NaOH added. The pH is equal to the pKa here, so the pKa was found to be 5.30. Using data from the equivalence point extrapolated from the graph, the molar mass of the unknown was calculated to by 148 grams per mole. Lastly, because there was only one region of
In this experiment three different equations were used and they are the Stoichiometry of Titration Reaction, Converting mL to L, and Calculating the Molarity of NaOH and HCl (Lab Guide pg. 142 and 143).
more it is in contact with the acid so it will react at a different
...3 occured by an acid attack after a complete removal of Ca(OH)2 at low pH as shown in Equation 2.10.
Initially, the concentration of the reagents decreases. As the concentration decreases, the rate of the forward reaction slows down. Meanwhile, the rate of the reverse reaction continually increases. Eventually, the rate of the forward reaction will equal the rate of the reverse reaction, and even though the reaction is still occurring, the change in concentration is insignificant. The equilibrium expression for the general reaction (1) is shown below:Keq is a value that is only dependent on temperature. If A, B, C, and D are mixed at unknown concentrations, the reagents will continuously react until equation (2) is true.