1. Which method used to determine the two equivalence points (pH meter or indica
ID: 1029890 • Letter: 1
Question
1. Which method used to determine the two equivalence points (pH meter or indicators) is more accurate? Justify this choice. 2. Even in a 0.050 M HCI solution an indicator is not all in the acid form. For methyl orange, what percentage of the indicator will be in each form? 3. The sensitivity of a spectrophotometer allows detection of I percent of one colored form of an indicator (for example HIn) in the presence of 99 percent of the other colored form (In). Based on this fact, over what pH range relative to its pK can an indicator be used if a spectrophotometer is employed? 4. A major buffering system in the blood is H,CO/HCO,. At first glance this would appear to be a poor choice. At the normal blood pH (7.4) a solution of HCO, and HCO, will change pH abruptly if small amounts of acid or base are added since the pk, of H,CO, is 6.4. Offer an explaination for this apparent contradiction. Support this argumeni with appropriate chemical equations. SAMSUNG F4 F8 F9 F10 F11 FV2 4 5 6 , 7 8 9 0Explanation / Answer
1 The use of an indicator is key in performing a successful titration reaction. The purpose of the indicator is to show when enough standard solution has been added to fully react with the unknown concentration. However, an indicator should only be added when necessary and is dependent upon the solution that is being titrated. Therefore, indicators must only be added to the solution of unknown concentration when no visible reaction will occur. Depending on the solution being titrated, the choice of indicator can become key for the success of the titration.
2 pH of 0.0Mor Hcl is slightly higher ie solution is almost neutral ( close to 7) so Indicator is not in all acid form
3 & 4 questions i dont have much idea
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