Materials and Apparatus:
- Burette
- 25cm³ pipette
- Retort stand
- Clamp
- Conical flask
- Pipette filler
- Phenolphthalein
- Sulphuric acid
- 25cm³ of 0.1 ml/dm³ Sodium hydroxide
Procedure:
1. Wash all equipment 3 times with distilled water
2. Rinse the burette with a little of the acid and then fill it up
3. Rinse the pipette with a little of the base before accurately transferring 25.0cm³ of it to a titration flask.
4. Place 2 to 3 drops of an appropriate indicator in the flask and titrate rapidly, until the end-point is reached
5. repeat experiment 2-3 times until you obtain precise results
Precautions
- Avoid parallax error when taking readings, by placing eyes perpendicular to the scale.
- In order to get accurate results make sure to titrate slowly and immediately stop once there is a colour change. Shaking the beaker from time to time also helps.
Observations:
As the HCL is titrated into the beaker containing NaOH, there is a visible colour change. The solution alters from colourless to a pale pink, once a suitable amount of HCL is added.
RESULTS
Table no.1
Calculations:
1. The concentration of NaOH=0.25mol dmˉ³
2. Number of moles in 25.0cm³ of NaOH=the volume the concentration which is 0.25 = 0.00625
3. The ratio of NaOH to H2SO4 = 2:1
4. Number of moles in the average acid titre = 0.00625
=0.003125
5. Concentration of H2SO4 = =
= 0.000246
6. A r of H2SO4 = 2(1)+32+4(16) =98
7. Concentration of H2SO4 =Concentration in mol dmˉ³ A r = 0.00025
=0.0245g dmˉ³
Equations
Chemical equation: 2NaOH (aq) + H2SO4 (aq) →Na2SO4 (aq) +2H2O (l)
Word equation: sodium hydroxide+ sulphuric acid → sodium sulphate + water
Ionic equation:2Na+(aq)+2OH-(aq)+2H+ (aq)+SO4-(aq) → 2Na+(aq)+SO4-(aq)+2H2O(l)
2OH-(aq) +2H+ (aq) →2H2O(l)
Limitations/Improvements
There was not a very large time span in order to do more experiments, thus only a small amount of results were obtained. However, had there been more time, more data could have been obtained hence the results would have been more valid.