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Thermo_Practice_Pt_1_Key[0]

# Thermo_Practice_Pt_1_Key[0] - (ΔE = q w ΔE is – if q>...

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3. a. Calculate the kinetic energy in joules of a 45g golf ball moving at 61m/s. (84 J) b. convert this energy to calories. (20 cal) c. What happens to this energy when the ball strikes a tree? (Energy is mostly transferred to the tree, released as heat.) 14. a. Write an equation the expresses the first law of thermodynamics. (ΔE = E sys + E surr = q + w) b. In applying the first law, do we need to measure the internal energy of the system? Explain. (measure change in E internal only b/c it represents changes in energy, not specific values) c. Under what conditions will the quantities q and w be negative? (q and w are negative when system loses heat or does the work. ) 18. A system releases heat to its surroundings and has work done on it by the surroundings. a. Sketch a box to represent the system, and use arrows to represent the heat and work transferred. b. Is it possible for ΔE to be negative for this process? Explain.

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Unformatted text preview: (ΔE = q + w, ΔE is – if q > w. ) system q = -w = + 24. The decomposition of limestone, CaCO 3 (s) into lime CaO(s) and CO 2 (g) at constant pressure requires the addition of 178.1kJ of heat/mole of CaCO 3 . a. Write a balanced thermochemical equation. (178.1 kJ + CaCO 3 CO 2 + CaO) (CaCO 3 CO 2 + CaO ΔH = 178.1kJ) b. Draw an enthalpy diagram for the reaction. 28. Consider the following reaction. 2Mg(s) + O 2 (g) 2MgO(s) ΔH = -1204kJ/mol a. exothermic or endothermic? (exothermic) b. Calculate the amount of heat transferred when 2.4g of Mg reacts at constant pressure. (-59 kJ) c. How many grams of MgO are produced during an enthalpy change of 96.0kJ? (6.43g MgO) d. How many kJ of heat are absorbed when 7.50g of MgO are decomposed in Mg and O 2 at constant pressure? (112 kJ) Reaction Progress E n e r g y...
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