Acetic acid, abbreviated HOAC, is about 1.3% dissociated in a 0.01M solution HOA
ID: 1005708 • Letter: A
Question
Acetic acid, abbreviated HOAC, is about 1.3% dissociated in a 0.01M solution HOAc_aq H^+ + Ac(aq) a)[H+] = a)[H+] = b)pH b)pH = c)Two indicators best used to bracket the pH of this solution c) and d) The color of methyl orange in this solution d) A chemist is given a bottle of carbonated water for pH testing. She adds methyl violet to a sample and finds the color is blue-violet. To another sample she adds Congo red and the color is blue. In what pH range has she bracketed the sample? A dilute ammonia solution used for washing window glass gives a blue color with the indicator thymolphthalein. What is the minimum pH of the solution?Explanation / Answer
1) HOAc --> H+ + AcO-
Initial 0.1 M 0 0
Change -(0.013 X 0.1) (0.013 X 0.1) (0.013 X 0.1)
Final 0.1-0.0013 0.0013 0.0013
a) [H+] = 0.0013
b) pH = -log[H+]
pH = -log[0.0013] = 2.88
c) The indicators which can be used for weak acid = Methyl orange and congo red
d) Colour of methyl orange in solution = Red
2) the pH range of methyl violet = 0- 2.5 ( it gives yellow green to violet)
The sample is blue violet so pH should be above 2.5
pH range of congo red = 3.0 - 5.0 ( below pH 3 blue and above 5 red)
with congo red colour is blue
So the pH range will be 2.5- 3
3) The pH range of 9.3 - 10.5
Below 9.3 colourless and above 10.5 blue
So the minimum pH is 10.5