colorimeter questions

hi i just wanted to check the answers to a few questions im having trouble with.

1. explain how diluting solutions can lead to errors in your measurements?

i think the answer is that when diluting you may not mix the solution enough hence leaving different absorption rates in different areas. does anyone have any other ideas?

2. Why is it neccessary to use carefully matched tubes in a colorimeter?

again i think its to do with different absorption rates. if the tube is thinner then light will pass through it more easily i think but im not too sure.

3. What general principles should be used when choosing a filter for a colorimetric investigation?

is it something to do with the opposites in a spectrum of visible light?

thanks! :wink:

Reply 1

herbal bug

from what i remember...

1. when diluting you will be accidentally always add to much or too little water. also yes if it is not done properly and mixed before being out into the cuvette of the colourimeter the substrate or the substance will not mix and you will get false results.

2. this is extremely simple when you think about it. When doing an experiment and you have to mention light being absoorbed, the cuvettes must be the same/matching. if not, it will not be a fair test as different amount of light will get through and as a result create wrong results.

3. it is often that yes. the opisite colour will be absorbed and all the other colours of the spectrum will be reflected away from the substrate. (do double check on this please) but you are correct.