Practice_Exam_Key 1 chem 107A

Practice_Exam_Key 1 chem 107A - 1.) In the table below,...

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1.) In the table below, fill in the columns labeled : q , w , ± U , ± H, with either a positive sign (+), negative sign (–), or zero (0) to predict the quantity for the system in each process described. Process q w ± U ± H Benzene freezing at its normal freezing point + Cooling a gas in a fixed volume container 0 Adiabatic compression of a monatomic gas 0 + + + 10 mL of ethanol evaporates at room temperature + + + 2.) It takes 330 Joules of energy to raise the temperature of 24.6g of benzene from 21.0°C to 28.7°C at constant pressure. What is the molar heat capacity of benzene at constant pressure? (M.W. benzene is 78.11 g/mol) q = C P dT = C P ± T q = n C P ± T C P = q n ± T = 330 J 24.6 g 78.11 g / mol ² ³ ´ µ · 28.7 ° ¸ 21.0 ° () C P = 136 J ¹ mol -1 ¹ K -1
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For the remaining questions, all work must be shown to receive full credit. 3.) Suppose that the molar internal energy of a substance over a limited temperature range could be expressed as a polynomial in T as: U ( T ) = a + bT + cT 2 . Find an expression for the constant- volume molar heat capacity at a given temperature T U = a + bT + cT 2 ± U T ² ³ ´ µ · V = C V = T ² ³ ´ µ · V a + bT + cT 2 C V = b + 2 cT 4.)
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Practice_Exam_Key 1 chem 107A - 1.) In the table below,...

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