Materials Required
- Burettes
- Conical flasks
- Stop-watch
- 0.1M sodium thiosulphate (Na2S2O3) solution
- 1M HCl
- Distilled water.
Procedure
Real Lab Procedure
- Take five clean conical flasks and label them as A, B, C, D and E respectively.
- Add 10, 20, 30, 40 and 50 ml of 0.1M sodium thiosulphate solution to the flasks A, B, C, D and E respectively.
- Then add 40, 30, 20 and 10ml of distilled water to the flask A, B, C and D respectively so that volume of solution in each flask is 50ml.
- Add 10ml of 1M HCl to the conical flask A.
- When half of the HCl solution has been added to the conical flask, start the stop- watch immediately.
- Shake the contents of the conical flask and place it on a white tile that has a cross mark at the centre.
- Go on observing from the top of the flask and stop the stop-watch when the cross marks just becomes invisible. Note down the time.
- Repeat the experiment by adding 10ml of 1M HCl to flasks B, C, D and E respectively and record the time taken in each case for the cross to become just invisible.
Simulator Procedure (as performed through the Online Labs)
- You can select the volume of sodium thiosulphate (Na2S2O3) solution using the slider.
- Drag the measuring jar to the conical flask to pour 0.1 M sodium thiosulphate (Na2S2O3) solution in it.
- Drag the measuring jar to the conical flask to pour distilled water in it.
- Click on the stopcock of the burette to add 5 ml hydrochloric acid into the conical flask.
- Click on the conical flask to shake it.
- Immediately, click on the stopcock of the burette to add another 5ml hydrochloric acid into the conical flask.
- You can get the time taken for the disappearance of the cross mark from the stopwatch.
- You can use the embedded worksheet to enter the values.
- You can plot a graph using the worksheet.
- To redo the experiment, click the ‘Reset’ button.
Note: Click on the ‘HELP’ button to see the instructions.
Observations
Flask No.
|
Volume of Na2S2O3 solution (ml) |
Volume of water (ml) |
Total volume of solution (ml) |
Conc. of Na2S2O3 solution (M) |
Volume of 1M HCl (ml) |
Time (t) taken for cross to become just invisible (s) |
1/t
(s-1) |
| A |
10 |
40 |
50 |
0.02 |
10 |
|
|
| B |
20 |
30 |
50 |
0.04 |
10 |
|
|
| C |
30 |
20 |
50 |
0.06 |
10 |
|
|
| D |
40 |
10 |
50 |
0.08 |
10 |
|
|
| E |
50 |
0 |
50 |
0.1 |
10 |
|
|
Plotting the Graph
Plot a graph between 1/t (in s-1) and the conc. of Na2S2O3 by taking 1/t along ordinate axis and conc. of Na2S2O3 along abscissa.
Conclusion
- The graph obtained is a straight line.
- 1/t is directly proportional to the concentration of Na2S2O3.
- Rate of the reaction between Na2S2O3 and HCl is directly proportional to the concentration of Na2S2O3, which is one of the reactant.
Precautions
- The apparatus must be thoroughly clean.
- Measure the volumes of sodium thiosulphate solution, HCl and distilled water very accurately.
- Use the same tile with the cross-mark for all observations.
- Complete the experiment at one time only so that there is not much temperature variation.
- When half of the HCl has been added to sodium thiosulphate solution, start the stop-watch immediately.
- View the cross-mark through the reaction mixture from top to bottom and from same height for all the observations.
