CHEM1B_QUIZ_3take home

CHEM1B_QUIZ_3take home - 2 SO 4 yield a buffer Calculate...

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Quiz 3 Chemistry 1B Name: ______________________ Spring 2009 ALL WORK MUST BE SHOWN FOR FULL CREDIT. 1. Suppose you are asked to prepare a buffer with pH = 7.40. What acid would be the best choice to prepare this buffer? Given that you had 500.0 mL of the acid, what mass of the corresponding sodium salt of the conjugate base would be required to make the buffer? What is the chemical formula of the sodium salt chosen? Assume the volume does not change on addition of the sodium salt. 1a. Chemical formula of Acid: _________________ 1b. Chemical Formula of the Sodium Salt: _________________ 1c. Molarity of Acid: ________________ 1d. Molarity of Conjugate Base: _________________
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2. Suppose that you add 5.0 mL of 0.10M H 2 SO 4 to a 20.0 mL solution of 0.10M NH 3 . Will the addition of the H
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Unformatted text preview: 2 SO 4 yield a buffer? Calculate the pH of the resulting solution. K b for NH 3 = 1.8 x 10-5 Optional Extra Credit 3. 25.00 mL of 0.100 M NH 3 is titrated by 0.100 M HCl. Methyl red can be used as an indicator for the titration. 3a. What volume of HCl is required to reach the equivalence point? 3b. Calculate the pH before any addition of HCl. 3c. Calculate the pH after adding 10.00 mL of HCl. 3d. Calculate the pH at the equivalence point. 3e. Calculate the pH after adding 40.00 mL of HCl. 3f. Use the pH values obtained in steps 3b-3e above to make a plot of the titration curve. Label the calculated pH values on the plot. Label the buffer region and the equivalence point. Was the choice of Methyl red indicator a good choice for this titration? Briefly explain....
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CHEM1B_QUIZ_3take home - 2 SO 4 yield a buffer Calculate...

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