3 if you needed to determine the pH of a solution in order to calculate the exac
ID: 569823 • Letter: 3
Question
3 if you needed to determine the pH of a solution in order to calculate the exact hydronium ion concentration, would t be more prudent to measure the pH using a natural indicator, such as red cabbage extract, or with a digital probe? Explain your answer 4 Would it be possible to use the color of a natural indicator to measure the pH of a dark household liquid, such as maple syrup? Explain your answer 5 some household chemicals, such as hydrogen peroxide and chlorine bleach, break down many organic molecules. Do you think it would be wise to try to measure the pH of these types of solutions using a natural pH indicator? Why or why not? Lab 16 pH Indicators 237Explanation / Answer
Ans. #3. Use of digital pH probe is preferred to calculate the exact [H3O+] in a solution because the probe detects exact point of neutralization.
# Natural pH indicators like cabbage extract show color change of neutralization near the actual endpoint of titration but NOT at exact point of neutralization. So, use of natural indicators would give an approximate [H3O+] in the solution.
#4. The endpoint of titration is characterized by sharp color change of the indicator molecules at point of neutralization.
When the solution being titrated (whose pH is to be determined) is already colored, the color change at endpoint can’t be detected clearly.
So, due to inability to detect the sharp color change of indicator in a colored solution, use of natural indicators is NOT preferred.
#5. The color change of an indicator is attributed to its protonation and deprotonation.
H2O2 and Ca(OCl)2 or other bleaches are strong oxidizing agents. So, they are likely to oxidize the indicator molecule and cause the loss of “indicator properties” of the molecule.
Therefore, use of indicators to determine the pH of household chemicals like hydrogen peroxide and bleach is NOT preferred.
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