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# e1ps10key - 1 Rearrange the Gibbs free energy equation G =...

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1. Rearrange the Gibbs free energy equation ( G = H - T S) to solve for the temperature at a phase transition. a. T = ( H - G)/ S b. T = H/ S c. T = - G d. T = - G/ S At a phase transition delta G = 0. The temperature dependence at a phase transition can be determined from thermodynamics. 2. What will happen to vapor pressure when non-volatile solute A is added to a pure solution B? a. Vapor pressure of A increases b. Vapor pressure of B decreases c. Vapor pressure doesn't change d. Boiling point decreases of A inrcreases. e. Boiling point of B decreases Adding a non-volatile solute (its vapor pressure is essentially zero) to any solvent, will decrease the measured vapor pressure of the solvent, by a factor equal to the solvents new mole fraction. 3. Rank the following salts from least to most soluble based on their H hydration : Al 3+ , 4800 kJ; I - , 244 kJ; K + , 350 kJ; Br - , 284 kJ. a. K + < I - < Br- < Al3+ b. Al 3+ < K+ < Br- < I- c. I - < Br - <K + <Al 3+ d. All ions are equally soluble. A higher charge density corresponds to a higher heat of hydration. The stronger the charge density of an ion the stronger the IMF, so it is going to be harder to pull it away from an ion of opposite charge. Hence, ions with large charge densities are harder to dissolve. 4. Which of the following is always true for phase diagrams? a. The slope of the melting curve is always positive b. The critical point will have a lower pressure than the triple point c. Only one phase exists on a phase boundary d. When going from left to right on the graph, pressure and temperature both increase along the condensation curve e. The critical point can be reached at 0K Melting curves can have a negative slope (ie water). The supercritical region is defined by an increase and pressure and temperature beyond the limits of the normal 3 phases. Phase boundaries represent equilibriums between two phases. 5. At what temperature will water boil on top of a mountain when normal boiling point is 100C at 1 atm. (You should not need to look at this graph to answer the question)

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a. Below 100C b. 100C c. Above 100C d. Water will not boil Pressure is lower at higher altitudes. Following the evaporation curve on the phase diagram from 1 atm to a lower pressure you see that temperature decreases. 6. Consider a 27 g sample of ice at 1 atm. Initially, the sample is frozen at -20 °C. How much heat must be added to the sample for it to become a liquid at 78 °C. Heat capacity of ice: 2 J/gK. Heat capacity of water: 4 J/gK. ∆H of melting: 330 J/g a. 9.5 kJ b. 18.4 kJ c. 5.3 kJ d. 10.6 kJ q = mc∆T (for the ice) + m∆H (for melting) + mc∆T (for the water) q = 27 g * 2 J/gK * 20 K + 27 g * 330 J/g + 27 g * 4 J/gK * 78 K q = 18.4 kJ 7. As the temperature of a solvent (increases/decreases), the solubility of (some/all) gases increases. a.
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e1ps10key - 1 Rearrange the Gibbs free energy equation G =...

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