pH Sensor

The reason why we have to calibrate the sensor is so it has range of pH levels to work from and by this range of pH levels it can work out a pH of a substance. The reason why we use a pH sensor instead of an indicator is because it is more accurate and when you use an indicator it is hard to find out what colour the substance changes and what pH level it has got.

Method

1. Open up the calibrate program on your computer.

2. Tell the computer the pH and the click the next button.

3. Buffer solution � solution of a known pH.

4. Set the first pH to 4 insert probe in to the solution then click next.

5. Clean the probe with distilled water then dry the probe with cotton.

6. Then insert the probe in to the second solution then click next.

7. Then clean the probe again with distilled water and dry the probe with cotton.

8. Then insert the probe into the last solution and then click next.

9. Then disconnect the pH sensor then reconnect it.

10. After this you should click set sensor range then select user calibration and then click the exit button.

11. Then you should clean the probe again with distilled water and clean it with a cotton piece.

12. To test if the experiment has worked you should put some water in to a beaker then put some water in to the water. The result that you should get is a pH level of seven.

13. To check if the experiment works try it again.

Results

The results that I got were

First reading = 7.62

Second reading = 7.52

Third reading = 7.38

The reason why the reading is going better is because the beaker is getting cleaner every time we put some fresh water in to it. It cleans the beaker from impurities and other dirt from the beaker.

Evaluation

It did not get to exactly pH level seven but I think that we would not be able to get exactly to pH level of seven because the water that we used was tap water, which has other ions in it which would affect the result that we got from the test. So I think the pH sensor is very accurate and is better than using an indicator which is hard to find out what pH level it has. To make the result much better for the pH sensor we could have used distilled water which would have had no other ions in it or other impurities which would have given us a better result. Also a pH sensor can test coloured solutions but the indicator can not do that. So this shows that a pH sensor is much more accurate to use then an indicator, if I was doing a test to find out a pH level of a solution I would use a pH sensor rather than an indicator.

pH Sensor

Strenghts

Weaknesses

Very accurate.

Takes along time.

Simple to use.

The probe needs to be cleaned after each test.

Give you an exact pH level.

Equipment is expensive.

Can test coloured solutions which an indicator would not be able to do.

You need a laptop or computer.

Easy to tell what pH level it has got.

Indicator

Strenghts

Weaknesses

Very fast.

Hard to tell the pH level.

Very simple to use.

Can not test coloured solutions.

Do not need any expensive equipment.

Is not very accurate.

Ahraz Ashraf 10N