1. Methyl red, HMR is a common acid-base indicator. In solution it ionizes accor
ID: 873946 • Letter: 1
Question
1. Methyl red, HMR is a common acid-base indicator. In solution it ionizes according to the equation:
red yellow
If methyl red is added to distilled water, the solution turns yellow. If a drop or two of 6 M HCl is added to the yellow solution, it turns red. If to that solution one adds a few drops of 6 M NaOH the color reverts to yellow.
a. Why does adding 6 M HCl to the yellow solution of methyl red cause the solution to turn red? (Note that in solution HCl exists as H+ and Cl? ions.)
b. Why does adding 6 M NaOH to the red solution make it turn yellow? (Note that in solution NaOH exists as Na+ and OH? ions.
c. How does increasing [OH?] shift Reaction 3 in the discussion section?
d. How would the resulting change in [H+] affect the ionization reaction of HMR?)
Explanation / Answer
a) Following Le Chatelier's principle, by adding more H+ ions, giving that we have an equilibrium, the reaction will tenf to produce more product, or HMR, which will turn the solution to a reddish color.
b) By adding OH- ions, you are consuming the hydrogen ions and turning them into water, which will also make an effect in the reaction, making it try to produce more products, or hydrogen ions, turning it yellow again.
c) It will tend to produce more product, hence it wil consume more rapidly the hydrogen ions, and left hydroxide ions will increase water's pH.
d) With more hydrogen ions, or in acidic solution, it will turn red. With less hydrogen ions, or in basic solution, it will turn yellow.
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