All questions are worth 25 points each. Show your work and circle your answers for full credit. OMIT ONE QUESTION by clearly writing OMIT in the space where you are to show your work, or by leaving the question COMPLETELY blank. Good luck.
1. Calculate the pH of the following solutions:
a) 0.10 M HNO3
b) 0.10 M HNO2
c) 0.10 M CH3NH2
d) 0.10 M NO2-
e) 0.10 M H2SO4
2. Consider the titration of 50.0 mL of 0.10 M acetic acid with 0.10 M NaOH. Calculate the pH at the following points along the titration curve.
a) Before any titrant is added;
b) After 12.5 mL of titrant is added;
c) After 25.0 mL of titrant is added;
d) After 50.0 mL of titrant is added;
e) After 60.0 mL of titrant is added.
3. Consider the titration of 50.0 mL of 0.050 M sodium bicarbonate (Na2CO3) with 0.10 M HCl. Calculate the pH at the following points along the titration curve.
a) Before any titrant is added;
b) After 12.5 mL of titrant is added;
c) After 25.0 mL of titrant is added;
d) After 37.5 mL of titrant is added;
e) After 50.0 mL of titrant is added.
4. A sample of cattle feed for feeder calves is measured for protein content using the Kjeldahl method. After 2.50 grams of the feed was digested with sulfuric acid, the solution was then made basic with NaOH, and the ammonia was distilled into 50.0 mL of 0.108 M HCl. The HCl was then back-titrated, requiring 15.8 mL of 0.0918 M NaOH. Given a gravimetric factor of 6.25 for the protein in the feed, calculate the percent protein in the feed sample.
5. A mixture that could possibly contain NaOH (MW = 40.00), Na2CO3 (MW = 105.99), and NaHCO3 (MW = 84.01) plus other inert material was analyzed by titration. When 1.8492 g of the mixture was dissolved in water and diluted to 500.0 mL in a volumetric flask, two 100.0 mL aliquots were removed by pipet. The first aliquot required 19.47 mL of 0.1005 M HCl to reach the phenolphthalein end point. The second aliquot required 46.99 mL of the same HCl solution to reach the modified methyl orange endpoint.
a) What specie(s) are present in the mixture?
b) What is the percentage of (each) component in the original sample?
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