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propaganda.net : Skole & Jobb
IndicatorsSkriv ut Utskrift
Naturfagsrapport på engelsk om indikatorer.
Engelsk - RapportForfatter:



Materials:
* 0.10 mol dm-3 NaOH solution
* 0.10 mol dm-3 HCl solution
* Two indicators labelled “A” and “B”
* Cell Well
* Drop counters
* Distilled water

Introduction:
The HCl solution has a pH of 1.0 and the NaOH has a pH of 13.0 initially. And in this experiment our goal is to determine:
1) The different colours.
2) And the pH interval where the colour changes for each indicator.

Procedure:
Please, look at the enclosure!

Data and Observations:
I took a few mL-s of HCl in the first well, and from this well, I transferred one drop to the next well and added nine other drops of water.

 

From this well number two, I transferred one drop of the solution to the next well, and added nine drops of water. Mixed it well, and continued like this until I had six wells in total.

 

Then, I used the same procedure to dilute NaOH, so that I ended up with six wells with NaOH solutions. And to each of the wells, I added a small amount of indicator “A”, and I did make observations and drew a conclusion, which is showed on the next page.

 

And after all this, then I repeated the entire procedure from the beginning, but instead of using indicator “A”, I used indicator “B”, which made that I ended up with six wells with HCl too.

Results:

Indicators

 Acidic

 Neutral

 Basic

 BTB (Bromothymol Blue)

 Yellow

 Green

 Blue

 MO (Methyl Orange)

 Red

 Orange

 Yellow


Conclusion and Explanations:
This experiment went as scheduled, and I got the correct colours mostly. The colours changed perfectly by mixing BTB (Bromothymol blue), MO (Methyl Orange). The mixtures got a colour when I poured one of the indicators into one of the acids, and I did this with all the acids. Therefore, I people will be able to see what is Acidic, Neutral and Basic. So, we can use this experiment to check that the solution is acidic, neutral or basic by adding an indicator. And the colour difference in the result gives the answer.

 

An indicator shows the acidity of a solution by help of colours. An acid is a compound that may donate H   ions. A base is a compound that accepts an H  ion.

 

When an acid is dissolved in water, an acidic solution is formed. When a base is dissolved in water, a basic solution is formed. A basic solution can neutralize an acidic solution. When we neutralize basic and acidic solution with each others, than a salt will be formed in water.

An acid-base indicator is a weak acid or a weak base. The undissociated form of the indicator is a different colour than the iogenic form of the indicator. An Indicator does not change colour from pure acid to pure alkaline at specific hydrogen ion concentration, but rather, colour change occurs over a range of hydrogen ion concentrations. This range is termed the colour change interval. It is expressed as a pH range.  

Source of error:
In case that the materials and the equipments are impure and dirty, or if I did took too much or too little of the substances that I used, then would it be possible to get incorrect results.




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