grade 12 titration stellenbosch version prac sheet only

8/9/2019 Grade 12 Titration Stellenbosch Version Prac Sheet ONLY

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Stellenbosch University Chemistry Outreach

Initiative

in collaboration with the WCED1

Grade 12 Practical !earner "and#

out

The titration of oxalic acid against sodium hydroxide

$ameDate

"i%h School

[1] MZ Moerat, Subject Advisor Physical Sciences, Western Cape Educationepart!ent, Moha!!ed"Moerat#$esterncape"%ov"&a

SU$C

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&'() O*+'I$ED ,-.

Titration of oxalic acid against sodium hydroxide.

SAFETY:

1. Oxalic acid is corrosive. It can be fatal if swallowed.

2. Sodium hydroxide is poisonous, harmful if inhaled, burns the skin and it

may be fatal if swallowed.

3. ll chemicals are ha!ardous. "lease consult your laboratory manual for

more information about why oxalic acid, sodium hydroxide and

sulphuric acid are ha!ardous.

#. $ear safety %o%%les and %loves when handlin% chemicals.

Formal experiment 1: Titration

Aim

&etermine the concentration of a %iven sodium hydroxide solution of unknownconcentration by titration a%ainst a standard solution of Oxalic acid.

Apparatus

'ou will need the followin% items for this experiment(

• ),1 mol.dm*3 Oxalic acid +standard solution

• -aO solution +unknown concentration

• "henolphthalein indicator

• &istilled water

• "ipette of volume 2/ ml

• 0eakers, volume 2/) ml and 1)) ml

• 0alance• Spatula

• rlenmeyer flask, volume 2/) ml

• olumetric measurin% flask, volume 1)) ml

• "iece of paper

• etort stand with base, retort clamp

• 0urette, volume /) ml

• $ash bottle

• &ropper

Method

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1 "ipette 2/ml of the standard acid solution into an rlenmeyer flask and add 3drops of phenolphthalein indicator.

2 inse your burette once with distilled water and then with small +/*1) mlportions of the -aO solution you have prepared, drainin% off the solutionthrou%h the burette tip.

3 4heck if your burette drains properly, no air bubbles are trapped in the tip andno leaks are apparent.

# 5ill the burette to the !ero mark with the -aO solution and make sure thatthe burette tip is full of solution. $ith a piece of paper towel, remove any dropof -aO han%in% from the tip.

/ 6ake a preliminary titration to learn approximately how the titration proceeds."lace a piece of white paper under the flask so that the colour of the solutionis easily observed. Swirl the flask and add the -aO solution. Occasionally

rinse down the walls of the flask with distilled water from your wash bottle.7itrate until the last drop of -aO solution leaves a permanent pink colour inthe solution. ead and record the position on the burette of the lowest point of the meniscus of the -aO solution.

8 -ow titrate at least three more samples of standard acid, bein% certain thatthe burette is refilled to the !ero mark with -aO solution and that you use aclean flask.

9 In this and subse:uent runs you may add -aO solution from the burette veryrapidly up to about 2 ml of the volume you estimate on the basis of your firsttitration. 7hen carefully add the rest of the base drop by drop so that you candetermine the endpoint accurately.

; ecord the results in a table. &ecide which values are accurate and calculatethe avera%e volume of -aO used.


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Writeup: !se the attached Mar"ing Memorandum as a guideline to do your #riteup:

$lanning: %& Mar"s'

+a &raw a labelled dia%ram of how you will set up your apparatus= +3

+b &escribe how you will collect, record and evaluate your data( +3

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(esults: %)* Mar"s'

+a Summarise your results in an appropriate table(

+b $rite a balanced e:uation for the reaction and calculate the unknownconcentration of the base +-aO(

*

grade 12 titration stellenbosch version prac sheet only

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