Acid-alkali Titration
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A few drops of methyl orange are added to a beaker of alkali. What will you observe when adding acid to beaker?
Methyl orange will change from yellow to orange to then red Acid - red Alkali - yellow Neutral- orange
A few drops of phenolphthalein are added to a breaker of acid. What will you observe when adding alkali?
Colour change from colourless to pink Acid - colourless Neutral - colourless Alkali - pink
How is water formed in a reaction between an acid and alkali?
H+ ions from acid react with OH- ions from alkali
List the apparatus required to carry out a titration
Burette Conical flask Clamp stand Pipette Small funnel White tile
Describe how to set up a titration and complete a titration
Use a pipette to add a known volume of alkali to a conical flask Add a few drops of indicator Fill the burette with acid using a funnel Open the tap of burette slowly add the solution (drop wise) to the conical flask, swirling to mix Close the Tap when the end point is reached Record the volume Repeat without indicator
What safety precautions should be taken when carrying out a titration?
Clear up spillages or broken glassware Wear safety goggles and gloves Fill burette below eye level using a funnel Be aware of the harmful effects of the chemicals use e,g irritant, corrosive
Why is an indicator used in titration?
To show when the end point has been reached
Why is a white tile use in a titration?
The white tile is placed under the reaction mixture to make the colour change easier to see
What is the purpose of repeating a titration?
To obtain concordant results, allow a mean titre to be calculated, and reduce the effect of random error.
Why is a trial titre carried out?
To find the rough volume require to reach end point To quickly check that the end point can be reached with the concentrations and volumes being used
What are concordant results
Titres which are within 0.20cm3 (or 0.10cm3) of each other
How do you calculate mean titre?
Add the 2 concordant results and divide by 2
Why is volumetric pipette use to measure the volume of acid or alkali added to the conical flask?
Greater accuracy than a measuring cylinder