Titration Calculations Using Mols- Paper 1 Flashcards
What is a titre?
Volume of known concentration required to neutralise the solution
What is n=cV
Amount in moles= concentration x volume
During a titration what type of reaction takes place?
An acid and alkali react in a neutralisation reaction.
How can we find the conc of an acid?
We can take a known volume of an acid and measure the volume of alkali it reacts with, then we can use some calculations to work out the concentration of the acid.
Describe the stages of titration is you want to discover the conc of an acid
A solution of alkali with a known conc is prepared.
Then the volume of the acid is measured using a pipette and is then added to a flask.
A suitable pH indicator is then added to show when the reaction reaches 7 (neutral)
Then add the alkali to the acid and measure the volume added to reach the end point using a burette.
Care must be taken to add it the acid dropwise, until one drop changes the colour of the indictaor.
What is the end point?
When a drop of alkali changes the colour of the indicator.
What can the burette do?
A burette has a scale that can measure volumes to the nearest 0.1cm3. It has a tap at the bottom to control the flow of alkali. (the volume measurements need to be read at eye level and from the bottom of the miniscus
How can you ensure you accurately measure the volume of alkali needed?
Care must be taken to add it the acid dropwise, until one drop changes the colour of the indictaor.
Why should you do a rough titration first?
To find out the volume approximately, then you need to now when to start adding alkali dropwise.
What must be done to make sure that the acid and alkali are mixed?
The glass must be swirled.
What should you use under the flask to highlight the colour change
A white tile
How do you get accurate results?
Titrations need to be repeated until the volume of the titre is consistent, they must agree to 1 decimal place and then the average volume should be worked out.
How could you workout the degree of uncertainty of your readings?
Calculate the range of your titration results.
What are common indicators used? Why?
Litmus, methyl orange and phenolphthalein. These indicators have only two colours and change sharply at end point.
Give an example of a mixed indicator?
Universal indicator, as it is a mixture of different indicators and has a variety of colours to signify pH
