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Quiz 1G (2)

# Quiz 1G (2) - putting the results from 2 and 3 in equation...

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Chem 104A/C Quiz 1 – January 22, 2010 Section AQB/AQC Kim Kyung Hoon PV = nRT R = 8.314 J/mol K = 0.08206 L atm/mol K 101.3 J = 1 L atm E = q + w q sys = -q surr w = -P ext V 1. (3pts) This question is about Intermolecular Forces (IMF). These are listed, below, in order of decreasing strength: ion-ion > ion-dipole > H-bonding > dipole-dipole > London Dispersion Forces Consider the two compounds, shown below. pentane water Write the strongest IMF for each separate compound : London Dispersion Force ____H- bonding_ _ Write the strongest IMF between the two compounds when they are mixed together: _____London Dispersion Force_ __ 2. (6pts) A gas is heated in a cylinder using 550 J of heat. A piston, under 2.0 atm pressure, compresses the gas from a volume of 10.0 L to a volume of 3.0 L. What is the change in internal energy ( E) of the gas during this process? ∆∆ E = q+w (1). q = 550J (2) w = -Pext * V = -2atm * (3 L – 10L) = 14Latm = 1418.2 J.(3)

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Unformatted text preview: putting the results from 2 and 3 in equation 1, ∆Ε = q+w = 550J + 1418.2 J = 1968.2 J. 3. (6 pts) An ideal gas in a cylinder expands against a constant external pressure of 1.0 atm. from a volume of 5.0 L to a volume of 13.0 L, at constant temperature. a) Determine the initial pressure of the gas (include units). Since the external pressure is constant, the initial pressure of the gas is same as the external pressure on the gas, therefore it is 1 atm. b) Calculate the work, w (in J) associated with the expansion of the ideal gas. In isothermal expansion, W is W= -nRT ln (Vfinal / V initial) (1). n = PV/RT = c) Knowing that ∆ E = 0 for ideal gases at constant Temperature, calculate the heat flow of the system in J. Is this an endothermic or exothermic process? Since ∆ E = 0 and W < 0 as we calculated in the problem above, Q>0. Therefore, this is an endothermic process....
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Quiz 1G (2) - putting the results from 2 and 3 in equation...

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