what chemical reaction takes place when you add universal indicator to an acid?

Question

what is the actual reaction, I know universal indicator is made up of a lot of indicators, but which one reacts to change the colour, what reaction takes place and why does the colour change. why doesn't it happen when Universal indicator is added to water?

Answer 1

we know that all acids are classified by having the H+ ion and so if you are testing for a acid it must then be this ion which reacts.

Therefore this means that the H+ ion must react in such a way with the indicater and so because whichever chemical the indicater is gains hydrogen, this can be thought of a hydrogenation reaction or a gain of hydrogen is a reduction reaction. The acid must then lose the hydrogen and so that is oxidised.

Hope this helps =] =]

Answer 2

Refer to this page regarding the Universal Indicator:
http://en.wikipedia.org/wiki/Universal_indicator

The way all pH indicators work is that they are complex organic dyes that can gain or lose a proton at specific pH levels -- the gqain or loss of the proton changes the bond structure and the electron conjugation in that bonding, and thus changes the wavelengths of light absorbed by the dye. See the following sites for more detail:
http://www.chemguide.co.uk/physical/acidbaseeqia/indicators.html
http://en.wikipedia.org/wiki/Acid-base_indicator

And, in fact, there IS a reaction that occurs when the Universal Indicator is added to water, but the result is the color you'd get for any aqueous solution with a pH of 7 (which is neutral!).

Hope that helps.

Answer 3

Daves answer explains it well so thumbs up to him. In organic dyes, such as those contained in indicator paper, it is electronic excitations which account for their colour.
These excitations typical come from an electron being excited from pi orbitals to a pi anti-bonding orbital. The amount of conjugation in a system will effect the energy separation between these two pi orbital and hence the wavelength/colour of absorbed light.

A H+ can add to heteroatoms in organic molecules which causes double bonds to shift around, which will reduce the conjugation and hence change the colour of the system. A base can rip hydrogen off of a molecule and increase conjugation, again changing the colour.

to answer your question quickly thereation that is taking place is an oxidation reaction

Answer 4

acid + alkali = salt + water. Acids are proton donors, they donate a H+ (aq) ion. (A hydrogen ion) Acids have pH values of under 7. Alkalis are proton acceptors, they donate a -OH (aq) ion. (A hydroxide ion). Alkalis have a pH fee of above 7. They react jointly to make a neutralisation reaction. The pH scale is a numerical scale from approximately 0 to fourteen which measures how good an acid or an alkali is. in case you utilize hydrochloric acid you will style a chloride salt. in case you utilize sulphuric acid you will style a sulphate salt. in case you utilize nitric acid you will style a nitrate salt. for occasion: hydrochloric acid + sodium hydroxide = sodium chloride + water in case you react an acid and an alkali you oftentimes get a salt + water. via ways, neutralization is while basse is blended with acid

Answer 5

There are several formulations for a universal pH indicator so a specific answer is not possible. However, the trick to making a universal indicator mixture is to arrange the color changes so that they "add" to new colors. For instance, a mixture of:

"A" low pH = yellow med. pH = clear hi pH=clear
"B" low pH = clear med. pH = red hi pH= red
"C" low pH = clear med. pH = clear hi pH = blue

would give the following colors as the indicators are progressively protonated by acid...

low pH = yellow, med. pH = orange, hi pH = lt. purple

Answer 6

The solution turns red