The Titration Of Vinegar And Bleach Solutions Biology Essay


This essay has been submitted by a student. This is not an example of the work written by our professional essay writers.

The aims of the experiments this time, is to find out the concentration of common food or household solution (vinegar and bleach solution in exact) by titration. And master the method of acid and base titration.

Vinegar is the ethanoic acid solution. The ethanoic acid is kind of organic compounds that the chemical formula is CH3COOH (Talk talk, 2010). The sodium hydroxide (NaOH) is a kind of base solutions that can neutralization with acid. The reaction equation is shown below (Lane, 2010a).

H+ + OH- → H2O

The main composition of bleach solution is an alkali metal hypochlorite. The alkali metal means the elements of Group I (FreePatentsOnline, 2010). Hypochlorite ion can react with iodide ion in an acid surrounding can provide iodine solution. There has two steps. The equations of this are shown below (Lane, 2010b).

First step: ClO- + 2I- + 2H+ → Cl- + I2 + H2O

Second step: I2(aq) + 2 S2O3 2-(aq) → 2 I-(aq) + S4O6 2-(aq)

Phenolphthalein is a colourless indicator that can appear a pink colour when meets base solution. The reaction is shown below (Beaumont, 2010).

Figure1. Theory of Phenolphthalein as an Indicator (Beaumont, 2010)


Equipments and Medicals

Vinegar (1 dm3)

Bleach (a bottle)

Sodium hydroxide (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 tubes; Funnel; Beaker; Burette; Conical flask; Pipette + pipette filler

Titration of Vinegar

Before starting the experiment, the phenolphthalein indicator was tested by acid and base solution. After pouring a little vinegar and NaOH solution each into a test tube, phenolphthalein indicator was added into each test tube. The colour changes were recorded.

The funnel was put on the top of the burette and pouring the NaOH solution into the funnel. Then, the level was adjusted to 0cm3 reading. Next, exactly 2.5cm3 vinegar was poured into the conical flask. 20cm3 water was poured into the same flask. After all these process, a few drops of phenolphthalein indicator was added into the flask. The flask with some white paper under it was put under the burette. As NaOH was starting added into the flask, the flask with mix solution was swirled. When the NaOH was down to 25cm3 level in burette, the burette was filled to the 0cm3 reading with some new NaOH using the same method that motioned before if the reaction did not come to the end point yet. As the experiment near ending point, some colour change appeared and disappeared by shaken the flask. The speed of adding NaOH was delay, one drop each time. Keep adding, until the colour occurs and not disappeared any more. Then, the end reading point was recorded and calculating the volume of NaOH for neutralization and takes a note.

The processes of experiment were repeated twice, and recording t he real initial and final burette reading.

Titration of Bleach

The burette was filled with sodium thiosulfate solution (Na2S2O3), and adjusts the reading to 0cm3. Then, 1cm3 bleach solution, 10cm3 potassium iodide solution (KI) and 10cm3 of dilute sulphuric acid (H2SO4) were add conical 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 starch indicator solution was added into flask just before the end-point that the colour of the solution in the flask was fades to pale yellow. After a blue-black colour appears, the Na2S2O3 solution was added dropwise and do not stop until the colour turned to colourless.

The processes of experiment were repeated twice, and recording t he real initial and final burette reading.


The observation of indicator tests is shown in table 1.


Observation (Colour changes)


From transparent to pink.


No change

Table 1 Indicator Experiment

The statistics in the Table1 is from experiment (A), the Titration of Vinegar.

Trial 1

Trial 2

Trial 3

Trial 4

Initial burette reading





Final burette reading





Volume of NaOH for neutralisation

(discarded statistics)




Volume of vinegar in the flask

(discarded statistics)




Table2. Titration of Vinegar Statistics

When the NaOH (aq) was added more than 30cm3, there has a pink colour appears but vanished as shaking the flask. The pink colour retained as the end-point was added.

The statistics in the Table2 is from experiment (B), the Titration of Bleach.

Trial 1

Trial 2

Trial 3

Initial burette reading




Final burette reading




Volume of Na2S2O3 for neutralisation




Volume of bleach in the flask




Volume of KI solution in the flask




Volume of H2SO4 in the flask




Table3. Titration of Bleach Statistics

The mixture in the flask appears a dark brown colour with a unique smell of I2. The colour stared to fading to paled yellow as the Na2S2O3 (aq) was added into the flask. After adding the starch indicator, the colour of mixture turns into a dark black-blue. When reached the end-point, the final mixture is colourless.


A) Calculate the concentration of H+ in vinegar.

a) Volume of vinegar in the flask is 2.5cm3

Average Volume of NaOH (aq) = (35.4+39.2) / 2= 37.3cm3

NaOH (aq) + CH3COOH (aq) → CH3COONa (aq) + H2O (aq)

Concentration: 0.1 mol dm-3 x mol dm-3 (x is the volume should be solved)

Volume: 37.3 cm3 2.5 cm3

x = (0.1 - 37.3 -10-3) / (2.5 -10-3)

≈ 1.49 mol dm-3

The concentration (a) of vinegar is 1.49mol dm-3.

b) Volume of vinegar in the flask is 1cm3

Average Volume of NaOH (aq) = 17.7cm3

NaOH (aq) + CH3COOH (aq) → CH3COONa (aq) + H2O (aq)

Concentration: 0.1 mol dm-3 x mol dm-3 (x is the volume should be solved)

Volume: 17.7 cm3 1.0 cm3

x = (0.1 - 17.7 -10-3) / (1.0 -10-3)

≈ 1.77 mol dm-3

The concentration (b) of vinegar is 1.77mol dm-3.

The average of concentration (a) and (b) is

(1.49+ 1.77) / 2 = 1.63 mol dm-3

∴The concentration of vinegar is about 1.63mol dm-3.

B) Calculate the concentration of ClO- in bleach solution.

Average volume of Na2S2O3 (aq) = (7.1+9.0+9.6) / 3 = 8.6 cm3

NaOCl (aq) + 2KI (aq) + H2SO4 (aq) → NaCl (aq) + I2 (aq) + K2SO4 (aq) + H2O (aq)

Concentration: 1 mol dm-3 x mol dm-3

Volume 10 cm3 a cm3

2Na2S2O3 (aq) + I2 (aq) → Na2S4O6 (aq) + 2NaI (aq)

Concentration: 0.1 mol dm-3 x mol dm-3

Volume 8.6 cm3 a cm3

n (KI) : n (I2) = 2 : 1

n (Na2S2O3) : n (I2) = 2 : 1

n (Na2S2O3): n (KI) = 1 : 1

n (NaOCl) : n (KI) = 1 : 2

n (Na2S2O3) = n (KI) = c - v = 1-10-10-3 = 0.01 mol, n (NaOCl) = 0.005 mole

∴Concentration of NaOCl = n / v = 0.005 / (8.6-10-3) ≈ 0.58 mol dm-3

Some non-accurate operation may affect the result. The judgment by using eyes about end-point may not accurate. Another factor that may influence the result is numerical reading not read by one person. This may cause the reading mistakes.


In conclusion, throw the experiments. The concentration of vinegar was found as about 1.63mol dm-3 by using the titration. Meanwhile, the concentration of ClO- in bleach solution is approximately 0.58 mol dm-3 by using the titration. The reactions are acid-base neutralization processes.

Writing Services

Essay Writing

Find out how the very best essay writing service can help you accomplish more and achieve higher marks today.

Assignment Writing Service

From complicated assignments to tricky tasks, our experts can tackle virtually any question thrown at them.

Dissertation Writing Service

A dissertation (also known as a thesis or research project) is probably the most important piece of work for any student! From full dissertations to individual chapters, we’re on hand to support you.

Coursework Writing Service

Our expert qualified writers can help you get your coursework right first time, every time.

Dissertation Proposal Service

The first step to completing a dissertation is to create a proposal that talks about what you wish to do. Our experts can design suitable methodologies - perfect to help you get started with a dissertation.

Report Writing

Reports for any audience. Perfectly structured, professionally written, and tailored to suit your exact requirements.

Essay Skeleton Answer Service

If you’re just looking for some help to get started on an essay, our outline service provides you with a perfect essay plan.

Marking & Proofreading Service

Not sure if your work is hitting the mark? Struggling to get feedback from your lecturer? Our premium marking service was created just for you - get the feedback you deserve now.

Exam Revision

Exams can be one of the most stressful experiences you’ll ever have! Revision is key, and we’re here to help. With custom created revision notes and exam answers, you’ll never feel underprepared again.