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SI Exam 3 Practice Problems

# SI Exam 3 Practice Problems - ENGR 145 Chemistry of...

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ENGR 145: Chemistry of Materials SI Practice Problems (Exam III) 1. Nitric oxide reacts with oxygen to form nitrogen dioxide via the following reaction: 2NO + O 2 Æ 2NO 2 You know heats of reaction for the following reactions: NO + O 2 Æ NO 3 Δ H = -0.52 kJ / mol NO 3 + NO Æ N 2 O 4 Δ H = -171.08 kJ / mol N 2 O 4 Æ 2NO 2 Δ H = 57.2 kJ / mol a. What is the heat of formation for this reaction? b. Assume the entropy change of this reaction is -58.6 J / mol K, independent of temperature. Is this reaction spontaneous at standard conditions (298K)? c. Under what conditions will this reaction be spontaneous?

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2. Titanium is commonly used in biomedical applications because of its biological compatibility within the human body. You have been asked to determined the change in entropy of titanium femur prosthesis to be used in hip replacement surgery, which is caused by the temperature change between the operating room (25°C) and the patient’s body (37°C). a. In order to calculate the change in entropy, you must first determined the specific heat of titanium using a calorimeter. You place 11.20 g of titanium initially at a temperature of 73.4°C into 60.00 g of water that is at a temperature of 20.0°C. The heat capacity of water is 4.184 J/(K*g) and the final temperature of the calorimeter was measured to be 21.2°C. b. Knowing that the atomic weight of titanium is 47.87 g/mol, calculate the molar heat capacity of titanium using your answer from part a.
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SI Exam 3 Practice Problems - ENGR 145 Chemistry of...

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