Acids, Alkali and Titrations

pH scale?

• from 0-14

• acids- 0 to 7

• alkali- 7 and above

• pH 0-3= strong acid

• pH 4-6= weak acid

• pH 8-10= weak alkali

• pH 11-14= strong alkali

• pH 7 is neutral (water)

Litmus colour in acid and alkali?

• acid- red

• alkali- blue

Phenolphthalein colour in acid and alkali?

• acid- colourless

• alkali- pink

Methyl orange colour in acid and alkali?

• acid- red

• alkali- yellow

acids and alkalis in water form?

acids forms a H+ ion- makes a solution acidic

alkalis forms a OH- ion- makes aqueous solution an alkali

Neutralisation reaction?

• occurs when an acid reacts with an alkali

• the H+ and OH- ion produces water

• Acid + Base = H2O + salt

Titrations?

A method of analysing the concentration of solutions

Method of doing a titration

• Use a pipette and a pipette filler and place 25cm³ of sodium hydroxide solution into a conical flask.

• Fill the burette with hydrochloric acid (do this below eye level)

• Record the starting point on the burette to the nearest 0.05 cm³

• Place the conical flask on a white tile and add a few drops of phenolphthalein indicator to the conical flask.

• Tip of the burette should be inside the conical flask

• Open the tap of the burette and let the acid flow through, keep vigorously swirling the conical flask.

• Swirl slowly when you think the end-point (colour change) is about to be reached.

• The indicator changes colour when all the alkali has been neutralised (phenolphthalein will turn pink)