nice powerpoint, for cape chemistry unit 1

1. ACID-BASE
TITRATION
CHEMISTRY

2. OBJECTIVES:
 Define the terms standard solutions and acid-base titration or volumetric
analysis.
 Recall that the reaction between an acid and a base is a neutralization reaction.
 Precisely explain how the change in color of the indicator tells the endpoint of a
neutralization reaction.
 Perform calculations to determine the molar concentration and mass
concentration of an unknown solution using a standard solution from acid-base
titration reactions with.

4. LAB ACTIVITY- LET US
EXPLORE!
•AIM OF LAB:
•To determine the concentration of
dilute hydrochloric acid in mol/dm3
and g/dm3 reagent using 0.3mol/dm3
of the standard solution; sodium
carbonate .

5. Calculating the mass of the sodium carbonate
required to prepare a solution of concentration
0.3mol/dm3- Formula
• Molar concentration ×molar mass ×Volume
1000

6. •Solution, Concentration and titrations!
•The concentration of a solution
• This refers to the amount of solute dissolved in a solvent to make a solution.
The units are usually expressed in moles per cubic decimeter (mol/dm3). This is
the molar concentration. Concentration of solution (mol/dm3) =
• number of moles of solute (mol)
• Volume of solution (dm3)
• In calculations involving solution concentration in mol/dm3 remember:
• To change mass in grams to moles
• To change cm3 to dm3 by dividing by 1000
• The moles of the solute = concentration x volume
• The volume of solution = moles of solute
•
Concentration

7. Example 1
• Calculate the concentration of a solution of potassium
hydroxide ( M = 56.0) containing 3.50 g of KOH in 125 cm3
of solution.

8. •Solution, Concentration and titrations!
•Mass concentrations calculations
• There is another way of expressing the concentration, known as
the mass concentration. This is the mass of solute dissolved in
1000 cm3 (1 dm3) of solution. The unit is g.dm-3 or g/dm3.
•
•
• Mass concentration = mass of solute
• Volume of solution (dm3)
• And
•
• Mass concentration = Molar concentration x molar mass of
solute / molar mass

9. Acid – base titrations
• A titration is used to determine the amount of substance present in a
solution of unknown concentration (analyte) by reacting it
quantitatively with a solution of known concentration (the standard
solution or titrant).
• The reaction between an acid and base is known as a neutralisation
reaction. The acid and base react with each other exothermically (heat
was given off) to produce salt and water. In this case the base must be
soluble (alkali).

10. Acid – base titrations
• We add the acid gradually to the alkali until the alkali has been neutralised
(completely used up).
• We use an acid-base indicator to find out when the acid has just reacted
completely with the alkali.
• The point at which neutralisation occurs is known as the end point of the
titration.
• At the end point, the colour of the indicator suddenly changes.
• Methyl orange and phenolphthalein are two examples of this type of
indicator.
• Their respective colours in an acidic and an alkaline solution are given:

11. Indicator Colour in an acidic solution Colour in an alkaline
solution
Methyl orange Red yellow
phenolphthalein Colourless pink

12. Calculating solution concentration by
titration
• In order to calculate solution concentration from
titrations results we need to know:
• the volume and concentration of the solution in the
burette eg. The acid
• the volume of the solution in the flask
• the balanced equation for the reaction

13. Remember…
Safety First!
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