Spectrophotometric Determination of a Food Dye

[@Zero_Cruz34]

This was such a wonderful and instructional video, great job and thank you!

[@RMalai]

Thank you. I ask my students to watch this before their lab.

[@poojagirish9663]

how did u make the stock solution?

[@acebelka2186]

Take stock Allura red SOLIDS (~496g/mol in molar mass) and calculate the volume of the container you want to use for your own stock solution; the container they have has a mol/L count(M) of 9.476*10^(-4)M.
For their case, if this was a 1L container, we would take that number in mol/L and multiply it by the 496 grams, divide by 1 mol and multiply by 1L which gets 0.4700096 grams. Therefore, for 9.476*10^(-4)M in a *1 liter* container, you need ~0.47 grams of Allura red solids; mix it all the way up with water and you get the same stock solution as them.
Your institution may require or even give a different stock solution (M), so keep that in mind.
Also keep in mind if you use a different volume, you will have to multiply by different amounts (e.g, 50mL would have to multiply 0.05L in the prior equation).
Good luck and good chemistry. 👍

[@melissanormoyle]

is it okay to touch the bottom of the beaker with the glass pipette when picking up stock dye? Will this cause air bubbles?

[@DrRichardMusgrave]

It's ok, provided you keep the pipette at an angle to the bottom of the beaker.

[@melissanormoyle]

@@DrRichardMusgrave Thank you!