below is the first step of a experiment. please read it and after that explain t
ID: 940910 • Letter: B
Question
below is the first step of a experiment. please read it and after that explain the answer of the question.
step 1:
1. Rinse the buret with water then with about 5 mL of the HCl standard solution. 2. Fill the buret with standardized 0.1 M HCl solution. Record the exact molarity of the acid as noted on the bottle. Open the stopcock and fill the tip of the buret. 3. Obtain an unknown sample, record its identification code. Weigh out 0.20g (to +/- 0.01 g) of the unknown sample and transfer it to a 125 ml Erlenmeyer flask. Add about 15 ml of distilled water and swirl to dissolve the sample. At this point the solution must be colorless. If the sample does not dissolve completely, don't worry, it will when you start the titration. 4. Add two (2) drops of phenolphthalein indicator. The solution will turn pink. 5. Record the initial volume of acid in the buret. Titrate with the standard HCl until the solution just turns colorless. It is extremely important not to over titrate! If you do over titrate, make sure that a note about it is written in your observations. This solution will be used in step 2, do not discard it! 6. Record the final volume of the HCl solution in the buret.
Question:
If the pH indicator used for the titration in step 1 changed color at a lower pH than phenolphthalein what effect would it have on the mass and what percent of the sodium carbonate determined in this experiment? Explain.
Explanation / Answer
If the pH change was at a lower value, not all of the base would have been neutralized well at the neutralization point shown by a low value indicator and thus lower amount of acid would have been used in such case. The mass thus calculated would be lower and so would be the percent calculated sodium carbonate determined by the experiment.
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.