Embedded Files
Using titration to investigate reacting volumes
THIS PRACTICAL IS FOR TRIPLE STUDENTS ONLY!
Background Information and Keywords
Background Information and Keywords
Keywords
Keywords
Burette - A very accurate piece of glassware used to measure volumes during a titration
Graduated Pipette - A very accurate piece of glassware used to measure volumes of liquid
Titre - A measurement of how much acid/alkali is added from the burette during the titration
Miniscus - the small curve formed by water tension at the top of the liquid
Indicator - a chemical which changes colour depending on the pH of a solutoin
pH - A value given to a substance describing how acidic or alkaline it is. The pH scale goes from pH 1 to pH 14
Background Information
Background Information
Acids react with alkalis in neutralisation reactions.
They react like this:
Acid + Alkali --> Salt + Water
We can use these reactions to work out the unknown concentration of an acid or an alkali with the help of an indicator, which can tell us when a neutralisation reaction is complete.
We do this using a practical called a Titration.
Other things you need to be able to do...
Other things you need to be able to do...
To do the practical
To do the practical
Know what an an acid, alkali and neutral solution are
Know what an indicator is and what it does
Know what a neutralisation reaction is
Calculate a mean for a set of data
Identify outliers in a set of data
To do the calculations (Higher Only)
To do the calculations (Higher Only)
Know how to balance an equation
Know how to rearrange an equation
Know how to convert units from cm3 to dm3 and back
Know how to calculate concentration in mol/dm3
Know how to calculate number of moles from volume and concentration
"How To Do It" Video
"How To Do It" Video
Watch this video to remind yourself how this practical is carried out.
Watch this video to remind yourself how this practical is carried out.
- What are the key steps to this practical?
- Why is each step done?
- What/why are the safety precautions taken?
This video also explains how to do a titration calculation (Important for Higher Tier)
This video also explains how to do a titration calculation (Important for Higher Tier)
Diagram
Diagram
Key Steps
Key Steps
Measure a volume of an unknown acid (e.g. 25cm3) using a volumetric pipette.
Place the acid in a conical flask and add a few drops of indicator (usually phenolphthalein or methyl orange).
Place the conical flask under a burette filled with alkali (e.g. NaOH) of a known concentration.
Measure the initial level of alkali in the burette
Slowly add alkali to the acid until a colour change happens. (showing the alkali has neutralised the acid).
Measure the final level of alkali in the burette
Calculate the total volume of alkali added to neutralise the acid
Key Questions from this Practical
Key Questions from this Practical
- Why do we use a graduated pipette to measure the acid, and not a measuring cylinder?
- What is the name of the special piece of equipment used for carrying out a titration?
- Why do we need to put an indicator in the acid?
- Why do we use an indicator like phenolphthalein or methyl orange instead of an indicator like universal indicator?
- Why do we place a white tile under the conical flask?
- Where is the correct point to read a meniscus to on a burette or graduated pipette? The top, middle or bottom of the curve?
Example Data
Example Data
Titre 1's result is much higher than titre 2,3 and 4.
This is called a rough titre. The other 3 show the endpoint to be around 18.9cm3.
We would work out a mean for Titre 2, 3 and 4 to find the actual value of HCl needed to neutralise the NaOH.
Titre 1 and titre 3 had refilled their burette to 0.0 cm3 before repeating their titration. But titre 2 and titre 4 just used the final reading as their first, using up the rest of the acid in the burette before refilling it.
Question Practice and Exam Questions
Question Practice and Exam Questions
Required Practicals Mastery Booklet - PAG 2 - Titrations.pdfPAG 2: Mastery Question Booklet
PAG 2: Mastery Question Booklet
This Mastery Booklet is filled with questions and exam questions to help you master this core practical. All answers and mark schemes are attached at the end.
Report abuse