Sum08_EXP3_Prelab%20%26%20Postlab%20Answer%20Key%20WebCT_sb

Sum08_EXP3_Prelab%20%26%20Postlab%20Answer%20Key%20WebCT_sb...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
Dr. S. Berniolles, Page 1 of 1 CHEM 6BL PRELAB/POSTLAB ANSWER KEY EXPERIMENT #3: THERMOCHEMISTRY PRELAB ANSWER KEY: 1. (0 points) See MSDS Information 2. (2 points) T water for the cold water will be (slightly) smaller than it should be. The calculated c metal will be smaller than the actual value. The calculated molar mass will be larger than it actually is. 3. (2 points) C c = 8.78 J/K 4. (2 points) T final = 21.14ºC 5. (2 points) q total = 99.8 kJ 6. (2 points) y = -0.42(5) + 40.98. The answer is: T f = 38.9ºC POSTLAB ANSWER KEY: 1. (1 point) M = 114.5 g/mol The calculated molar mass is closest to Indium (In: element #49). 2. (1 point) 6.21 × (11.64 – 8.5278) = 19.3 (three sig. figs total) 3. (1 point) The temperature declines because heat is lost to the surrounding environment, through the calorimeter and to the calorimeter itself (i.e., an imperfect calorimeter).
Background image of page 1
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: 4. (2 points) 100 g of ice . Two reasons: 1) ice has a large amount of energy to accept (i.e., to cool) from its H fusion term, and 2) water (and even ice) has a much larger specific heat capacity than Magnesium (4.18 J/K·g (or 2.03 J/K·g) vs. 1.024 J/K·g). 5. (2 points) 7 cubes of ice 6. (1 point) 106,300 J or 106.3 kJ 7. (1 point) q cold = (m cold c ∆ T cold ) + (C c ∆ T cold ) = -q hot If q hot remains the same and C c is smaller for the Pyrex glass (and m & c do not change), then ∆ T must be larger with glass. Hence, the temperature change of the water must be greater with a Pyrex glass calorimeter . 8. (1 point) ∆ H = –1367 kJ...
View Full Document

This note was uploaded on 08/04/2009 for the course CHEM 630888 taught by Professor Berniolles during the Spring '09 term at UCSD.

Ask a homework question - tutors are online