Methyl orange in its structure has a ion of Na+. my question is, after dissolving methyl orange in water, what will happen to that ion? Dose it form NaOH in reaction with water ? consequently, dose the H+ make a combination with methyl Orange? Or if not, do you know what will take place?
Methyl Orange (MeOrOH) is a weak base. The undissociated base is red, and anion of Methyl Orange formed on ionization is yellow.
MeOrOH MeOr+ + OH-
RED YELLOW
at a pH value of < 4 it looks red, at pH values > 4 it looks red, at pH = 4 it is orange
It also contains a sulfonate group this is a highly acid group comparable in acidity to a strong mineral acid. It is this sulfonate group that exists as the sodium salt in methylorange, the sodium sulfonate moiety renders methyl orange highly soluble, because the sulfonate group of methylorange is as its anion paired with a sodium, and because it is the salt of a strong acid and a strong base (like NaCl) this ion pair is neutral, and plays no role in the color change. Thus the Na+ ion will not form NaOH, and will not effect the pH.
Thank you so much for answering my question, just i have two questions.
first, I cannot find OH group in the structure of the methyl orange. If i made a mistake, i will appreciate your clarification (please check the picture that i found in the PubChem.)
second, I deduced that in water methyl orange separates to an anion (R--SO3-) and a cation (Na+), am i right?
Philip G Penketh
It's a base in that it generates an -OH from a bound water if the structure given here (N:OH2) represents one of the methyl orange nitrogens with the colon (:) representing the nitrogen's lone pair of electrons hydrogen bonded to a water to give N:OH2 this will ionize to generate an -OH and N:H+ just like an aqueous solution of ammonia generates an alkaline solution (NH3 + H2O NH4+ + -OH) . So this is the source of the -OH, I should have produced a small figure to illustrate my point rather than try to just used text. You are correct that the R--SO3Na ionizes to give R--SO-3 + Na+.
That will be great if it is possible, you use a figure to explain the first matter.
thank you in advance for your time.
This image explains it completely. Thank you so much.
Philip G Penketh