RACI Titration Stakes Victoria 2007

RACI Titration Stakes – Victoria 2010

THE ROYAL AUSTRALIAN CHEMICAL INSTITUTE Inc

Victorian Branch

Titration Stakes

Australian National Chemical Analysis Competition -Victorian Section

The Royal Australian Chemical Institute (RACI) invites your school to participate in the 2010

Titration Stakes Competition. The competition is open to students in Years 11 and 12, who must compete in teams of three.

Section 1 Victorian Titration Stakes

This competition is undertaken in the school on any day during the first three

weeks of June. Each Team will be required to prepare solutions and titrate two

samples supplied by The Royal Australian Chemical Institute. A list of rules and competition details is attached.

The entry fee is $25.00 per team.

Each team that gains a place in the top ten per cent of the teams will win a book for their school library and an invitation to represent Victoria in the National Finals. Each member of the team will win a prize to the value of $25.00. All participants will receive a Certificate of Participation.

Section 2 National Finals

To be eligible to compete in the National Finals, a team must gain a place in the top ten percent of the teams that entered the Victorian competition. The National Finals will be held in September.

Teams who qualify for the National Competition will be notified later. All national finalists receive a gold or silver medal and a team plaque is awarded to outstanding teams. The Victorian team that performs the most accurate analysis will win books to the value of $500.00 for their school and will hold the RACI Victorian Branch St Bernard's College plaque for one year.

We look forward to receiving your school's entry for the competition. Good luck!

Professor Philip Marriott

President, Victorian Branch

Competition Rules and Prizes

RULES

1. Each Team must consist of three Members. Members of a team will be

undertaking Year 11 or 12 Chemistry. The members of any given team do not have to be all from the same class or year level.

2. Schools may enter as many teams as they wish. All entries, accompanied by the entry fee, must be received by 14 May 2010.

3. The experimental procedure as written will be used.

4. The experimental work and calculations are to be performed within a

two-hour period.

5. All result sheets are to be submitted to the RACI Victorian Branch Office by 5 July 2010.

6. Professor Philip Marriott (Victorian Branch President) and Ms Sandra Sdraulig (Victorian Branch Analytical Chemistry Group) will be adjudicators. Prizes will be awarded by them solely on the basis of results and worksheets returned by the specified date.

7. Arrangements for the delivery of the "unknown" vinegar and any other material will be made with each school organiser.

NOTE

If a team member from the state competition is unable to compete in the National

finals, the school may substitute ONE team member only, provided that the

school can sign a declaration that this is due to unforeseen circumstances.

PRIZES

1. All participating team members will be provided with a certificate indicating participation in this analysis competition signed by the Branch President.

2. The top ten per cent of teams in the Victorian competition will be selected for the National Finals. All teams selected for the National Finals will win a prize to the value of $25.00 for each team member and a book for their school.

3. The most accurate Victorian Team in the National Finals will win books to the value of $500.00 for its school and will hold the RACI Victorian Branch St Bernard's College plaque for one year.

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EXPERIMENTAL PROCEDURE

You are required to determine the percentage by mass of ethanoic acid (acetic acid) in two samples of vinegar that will be supplied by RACI. One sample is marked "A" and the other is marked "B".

To do this, you are to prepare a solution of 0.1M sodium hydroxide which is to be standardised

against potassium hydrogen phthalate using the following reaction:.

NaOH(aq) + KH(C8H4O4)(aq) → NaK(C8H4O4)(aq) + H2O(l)

You will then perform a titration using the standardised sodium hydroxide to determine the concentration of ethanoic acid (acetic acid) in vinegar:

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

Safety: Follow your teacher’s instructions about safety precautions to ensure this analysis is performed safely.

Procedure:

1. To prepare the sodium hydroxide solution, weigh 4.0 g of sodium hydroxide into a 1 litre volumetric flask. Add approximately 200 mL of distilled water to the flask to dissolve the pellets. When dissolved, fill to the mark with distilled water.

2. Weigh about 0.5 g of potassium hydrogen phthalate into a 250 mL

conical flask and record its mass. Add about 50 mL of distilled water and swirl the flask to dissolve the solid material. Add two drops of prepared phenolphthalein indicator to the flask and titrate against the sodium hydroxide solution to the end point. Calculate the molarity of the sodium hydroxide. Repeat, at least twice or until reproducible results are obtained, and hence determine the mean concentration of the sodium hydroxide solution.

3. Weigh as accurately as possible about 20.0 g of sample A of vinegar into a

100 mL volumetric flask and record its mass. Dilute to 100 mL using distilled water.

Pipette a 20 mL aliquot into a 250 mL conical flask, add 50 mL of distilled water,

two drops of phenolphthalein and titrate against the standardised sodium hydroxide.

Repeat at least twice, or until reproducible titres are obtained. Use your results to caklculate the percentage by mass of ethanoic acid (acetic acid) in the sample. If a 20 mL pipette is not available, please use an alternative volume pipette and adjust the calculations accordingly.

4. Repeat step 3 for the determination of sample B.

Calculations: As per result sheet. Show all workings on a work sheet.

Australian National Chemical Analysis Competition Victorian Section

RESULTS SHEET 1

NAME

(TEAM MEMBERS):......

......

SCHOOL:......

ORGANISER:......

SCHOOL ADDRESS:......

………………………………………………………………………………………………

...... PHONE::...... FAX:......

Standardisation of sodium hydroxide solution:

Molar mass potassium hydrogen phthalate: ………………… g mol-1

Molar mass sodium hydroxide: ………………… g mol-1

Titration results (report all results):

Equation for the titration: NaOH(aq) + KH(C8H4O4)(aq) → NaK(C8H4O4)(aq) + H2O(l)

Mean molarity of sodium hydroxide solution ...... M

RESULTS SHEET 2

Sample A % ethanoic acid (acetic acid)

Mass of vinegar ...... g

Molar mass ethanoic acid ...... g mol-1

Volume of diluted sample used for titration: ………………… mL

Titration results (report all results):

Mean titre: ………………….. mL

Equation for the titration: NaOH(aq) + CH3COOH(aq) → CH3COONa(aq) + H2O(l)

Percentage ethanoic acid (acetic acid) in sample A: ………………………….. %(w/w)

Sample B % ethanoic acid (acetic acid)

Mass of vinegar ...... g

Molar mass ethanoic acid ...... g mol-1

Volume of diluted sample used for titration: ………………… mL

Titration results (report all results):

Mean titre: ………………….. mL

Equation for the titration: NaOH(aq) + CH3COOH(aq) → CH3COONa(aq) + H2O(l)

Percentage ethanoic acid (acetic acid) in sample B: ………………………….. %(w/w)

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