Acids, alkalis and titrations Flashcards
What do acids produce?
Acids produce acidic solutions and hydrogen ions, H+
What do alkalis produce?
Alkalis form alkaline solutions and hydroxide ions, OH-
What is the pH value for acids?
pH values lower than 7
What is the pH value for alkalis?
pH values greater than 7
What is a neutral solution?
A pH value of 7 - not acidic and not alkaline
What colours does litmus paper turn?
Acids = red Alkaline = blue Neutral = purple
What colour does methyl orange turn?
Acids = red Alkaline = yellow Neutral = yellow
What colour does phenolphthalein turn?
Acids = colourless Alkaline = pink Neutral = colourless
What is the purpose of the pH scale?
To measure the acidity or alkalinity of a solution
How do you carry out an acid-alkali titration?
1) Use the pipette and pipette filler to add 25 cm3 of alkali to a clean conical flask.
2) Add a few drops of indicator and put the conical flask on a white tile.
3) Fill the burette with acid and note the starting volume.
4) Slowly add the acid from the burette to the alkali in the conical flask, swirling to mix.
5) Stop adding the acid when the end-point is reached (the appropriate colour change in the indicator happens). Note the final volume reading.
State the definition of a titration
A quantitative procedure in which two solutions react in a known ratio, so if the concentration of one solution is known and the volumes of both are measured, the concentration of the other solutions can be determined
State what happens when an acid is neutralised
When an acid reacts with an alkali it produces a salt and water. This reaction is called neutralisation. The alkali has neutralised the acid by removing its H+ ions, and turning them into water.
