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Chapter 6 Thermochemistry 113 q = = J = 400 °C finally = Tf - Tᵢ. Rearrange to solve for Tf. g X 0.235 °C = + Tᵢ = 400 + 27.0 = 430 Check: The units (°C) are correct. The magnitude of the answer (430) makes physical sense because such a large amount of heat is absorbed and there are a small mass and specific heat capacity. The temperature change should be very large. The temperature change should be less than that of the gold because the specific heat capacity is greater. (c) Given: 25 g aluminum; = 27.0 °C; q = 2.35 kJ Find: Conceptual Plan: kJ J and pull Cₛ from Table 6.4 then m, Cₛ, q AT then Tᵢ, 1000J 0.903 J 1kJ °C q = Solution: 2.35 X = 2350 then q = Rearrange to solve for T. q = = mCₛ = finally AT = Tf Rearrange to solve for Tf. 25 g X °C = + Tᵢ = 104.10 °C + 27.0 °C = 130 Check: The units (°C) are correct. The magnitude of the answer (130) makes physical sense because such a large amount of heat is absorbed and there is such a small mass. The temperature change should be less than that of the silver because the specific heat capacity is greater. (d) Given: 25 g water; Tᵢ = 27.0 °C; q = 2.35 kJ Find: Conceptual Plan: kJ J and pull Cₛ from Table 6.4 then m, Cₛ, then AT J q = AT = Tf Tᵢ 1000J Solution: 2.35 X = 2350 J then q = Rearrange to solve for q = = = 22.488 °C finally = Rearrange to solve for Tf. 25 °C Tf = + = 22.488 + 27.0 °C = 49 °C Check: The units (°C) are correct. The magnitude of the answer (49) makes physical sense because such a large amount of heat is absorbed and there is such a small mass. The temperature change should be less than that of the aluminum because the specific heat capacity is greater. 6.51 Given: = 0.0 L; Vf = 2.5 L; P = 1.1 atm Find: (J) Conceptual Plan: Vᵢ, Vf V then P, W (J) -PAV Solution: V = Vf Vᵢ = 0.0L = 2.5 L then = PAV = 1.1 atm X X 101.3J = 280 J or -2.8 X 10² J Check: The units (J) are correct. The magnitude of the answer (-280) makes physical sense because this is an expansion (negative work) and we have atmospheric pressure and a small volume of expansion. 6.53 Given: q = 565 J absorbed; = Vf = 0.85 L; P = 1.0 atm Find: Conceptual Plan: Vᵢ, V and interpret language to determine the sign of the heat q = then P, W (L atm) (J) finally q, = -PAV = q + atm Copyright © 2017 Pearson Education, Inc.