The purposes of the experiments this clip, is to happen out the concentration of common nutrient or family solution ( acetum and bleach solution in exact ) by titration. And master the method of acid and base titration.
Vinegar is the ethanoic acerb solution. The ethanoic acid is sort of organic compounds that the chemical expression is CH3COOH ( Talk talk, 2010 ) . The Na hydrated oxide ( NaOH ) is a sort of base solutions that can neutralization with acid. The reaction equation is shown below ( Lane, 2010a ) .
H+ + OH- > H2O
The chief composing of bleach solution is an alkali metal hypochlorite. The alkali metal means the elements of Group I ( FreePatentsOnline, 2010 ) . Hypochlorite ion can respond with iodide ion in an acid environing can supply iodine solution. There has two stairss. The equations of this are shown below ( Lane, 2010b ) .
First measure: ClO- + 2I- + 2H+ > Cl- + I2 + H2O
Second measure: I2 ( aq ) + 2 S2O3 2- ( aq ) > 2 I- ( aq ) + S4O6 2- ( aq )
Phenolphthalein is a colorless index that can look a pink coloring material when meets base solution. The reaction is shown below ( Beaumont, 2010 ) .
Method
Equipments and Checkups
- Vinegar ( 1 dm3 )
- Bleach ( a bottle )
- Sodium hydrated oxide ( 0.1mol/ 1 dm3 ) ( NaOH )
- Phenolphthalein Indicator
- Sodium thiosulphate solution ( concentration: 0.1mol/ 1 dm3 ) ( Na2S2O3 )
- Potassium Iodide ( 1mole ) ( KI )
- Dilute Sulphuric Acid ( H2SO4 )
Test tubing ; Funnel ; Beaker ; Burette ; Conical flask ; Pipette + pipette filler
Titration of Vinegar
Before get downing the experiment, the phenolphthalein index was tested by acid and base solution. After pouring a small acetum and NaOH solution each into a trial tubing, phenolphthalein index was added into each trial tubing. The coloring material alterations were recorded.
The funnel was put on the top of the burette and pouring the NaOH solution into the funnel. Then, the degree was adjusted to 0cm3 reading. Following, precisely 2.5cm3 acetum was poured into the conelike flask. 20cm3 H2O was poured into the same flask. After all these procedure, a few beads of phenolphthalein index was added into the flask. The flask with some white paper under it was put under the burette. As NaOH was get downing added into the flask, the flask with mix solution was swirled. When the NaOH was down to 25cm3 degree in burette, the burette was filled to the 0cm3 reading with some new NaOH utilizing the same method that motioned before if the reaction did non come to the terminal point yet. As the experiment near stoping point, some colour alteration appeared and disappeared by agitating the flask. The velocity of adding NaOH was hold, one bead each clip. Keep adding, until the coloring material occurs and non disappeared any more. Then, the terminal reading point was recorded and ciphering the volume of NaOH for neutralisation and takes a note.
The procedures of experiment were repeated twice, and entering T he existent initial and concluding burette reading.
Titration of Bleach
The burette was filled with Na thiosulfate solution ( Na2S2O3 ) , and adjusts the reading to 0cm3. Then, 1cm3 bleach solution, 10cm3 K iodide solution ( KI ) and 10cm3 of dilute sulfuric acid ( H2SO4 ) were add conelike flask. The flask was moved under the burette with a white paper under it, the solution in the burette was released into the flask and it was swirled continuously. The amylum index solution was added into flask merely before the end-point that the coloring material of the solution in the flask was slices to blanch yellow. After a bluish black coloring material appears, the Na2S2O3 solution was added dropwise and make non halt until the coloring material turned to colourless.
The procedures of experiment were repeated twice, and entering T he existent initial and concluding burette reading.
Consequence
When the NaOH ( aq ) was added more than 30cm3, there has a pink coloring material appears but vanished as agitating the flask. The pink coloring material retained as the end-point was added.
The mixture in the flask appears a dark brown coloring material with a alone odor of I2. The coloring material stared to melting to blanch yellow as the Na2S2O3 ( aq ) was added into the flask. After adding the amylum index, the coloring material of mixture turns into a dark black-blue. When reached the end-point, the concluding mixture is colorless.
Discussion
Some non-accurate operation may impact the consequence. The judgement by utilizing eyes about end-point may non accurate. Another factor that may act upon the consequence is numerical reading non read by one individual. This may do the reading errors.
Decision
In decision, throw the experiments. The concentration of acetum was found as approximately 1.63mol dm-3 by utilizing the titration. Meanwhile, the concentration of ClO- in bleach solution is about 0.58 mol dm-3 by utilizing the titration. The reactions are acid-base neutralisation procedures.
