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Exam 8: Thermodynamics: The First Law

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Question 41

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Calculate the lattice enthalpy of potassium fluoride from the following data. enthalpy of formation of K(g) : +89 kJ.mol^-1 First ionization energy of K(g) : +418 kJ.mol^-1 Enthalpy of formation of F(g) : +79 kJ.mol^-1 Electron affinity of F(g) : +328 ( $\Delta$ H = -328) kJ.mol^-1 Enthalpy of formation of KF(s) : -567 kJ.mol^-1

A) 1481 kJ.mol^-1
B) 825 kJ.mol^-1
C) 904 kJ.mol^-1
D) 497 kJ.mol^-1
E) 347 kJ.mol^-1

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Question 42

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Calculate the Br-Br bond enthalpy given the standard enthalpies of formation for Br₂(g) and Br(g) ,30.7 and 112 kJ.mol^-1 ,respectively.

A) 193 kJ.mol^-1
B) 255 kJ.mol^-1
C) 143 kJ.mol^-1
D) 81 kJ.mol^-1
E) 30.7 kJ.mol^-1

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Question 43

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What equation corresponds to the standard enthalpy of formation of gaseous hydrogen atoms,which,at 298 K is +217 kJ.mol^-1 ?

Use the following information to determine the standard enthalpy of formation of NH₃(g) . N-H bond enthalpy = 390 kJ.mol^-1 $\Delta$ H_f ^$\circ$ (H(g) ) = 217.9 kJ.mol^-1 $\Delta$ H_f ^$\circ$ (N(g) ) = 472.6 kJ.mol^-1

The combustion of 1 mole of octane,C₈H₁₈(l) ,to produce carbon dioxide and liquid water has $\Delta$ H_r = -5471 kJ.mol^-1 at 298 K.What is the change in internal energy for this reaction?

Calculate the enthalpy change that occurs when 1 lb (454 G) of mercury freezes at its freezing point (234.3 K) .The standard enthalpy of fusion of mercury is 2.29 kJ.mol^-1.

Calculate the lattice enthalpy of calcium oxide from the following data. enthalpy of formation of Ca(g) : +178 kJ.mol^-1 First ionization energy of Ca(g) : +590 kJ.mol^-1 Second ionization energy of Ca(g) : +1150 kJ.mol^-1 Enthalpy of formation of O(g) : +249 kJ.mol^-1 First electron affinity of O(g) : +141 ( $\Delta$ H = -141) kJ.mol^-1 Second electron affinity of O(g) : -844 ( $\Delta$ H = +844) kJ.mol^-1 Enthalpy of formation of CaO(s) : -635 kJ.mol^-1

How much heat is required to vaporize 50.0 g of water if the initial temperature of the water is 25.0 ^$\circ$ C and the water is heated to its boiling point,where it is converted to steam? The specific heat capacity of water is 4.18 J.( ^$\circ$ C) ^-1.g^-1 and the standard enthalpy of vaporization of water at its boiling point is 40.7 kJ.mol^-1.

If the standard enthalpy of combustion of octane,C₈H₁₈(l),at 298 K is -5471 kJ.mol^-1 ,calculate the standard enthalpy of formation of octane.The standard enthalpies of formation of carbon dioxide and liquid water are -393.51 and -285.83 kJ.mol^-1 ,respectively.

How much work is done by a person of mass 185 kg who climbs a ladder to the top of his house,a total of 15.0 m?

Combustion reactions can be exothermic or endothermic.

Calculate the enthalpy change that occurs when 1.00 kg of acetone condenses at its boiling point (329.4 K) .The standard enthalpy of vaporization of acetone is 29.1 kJ.mol^-1.

A piece of a newly synthesized material of mass 12.0 g at 88.0 ^$\circ$ C is placed in a calorimeter containing 100.0 g of water at 20.0 ^$\circ$ C.If the final temperature of the system is 24.0 ^$\circ$ C,what is the specific heat capacity of this material?

Calculate the standard reaction enthalpy for the following reaction. CH₄(g) + H₂O(g) $\rightarrow$ CO(g) + 3H₂(g) Given: 2H₂(g) + CO(g) $\rightarrow$ CH₃OH(l) $\Delta$ H° = -128.3 kJ.mol^-1 2CH₄(g) + O₂(g) $\rightarrow$ 2CH₃OH(l) $\Delta$ H° = -328.1 kJ.mol^-1 2H₂(g) + O₂(g) $\rightarrow$ 2H₂O(g) $\Delta$ H° = -483.6 kJ.mol^-1

When nitrogen gas expands from 3.00 to 6.00 L and 2.00 kJ of energy is transferred as heat to the nitrogen in a cylinder fitted with a piston at an external pressure of 2.00 atm,against this constant pressure,what is $\Delta$ U for the process?

Calculate the standard reaction enthalpy for the reaction. N₂H₄(l) + H₂(g) $\rightarrow$ 2NH₃(g) Given: N₂H₄(l) + O₂(g) $\rightarrow$ N₂(g) + 2H₂O(g) $\Delta$ H° = -543 kJ.mol^-1 2H₂(g) + O₂(g) $\rightarrow$ 2H₂O(g) $\Delta$ H° = -484 kJ.mol^-1 N₂(g) + 3H₂(g) $\rightarrow$ 2NH₃(g) $\Delta$ H° = -92.2 kJ.mol^-1

What mass of ethanol,C₂H₅OH(l) ,must be burned to supply 500 kJ of heat? The standard enthalpy of combustion of ethanol at 298 K is -1368 kJ.mol^-1

Calculate the lattice enthalpy of silver chloride from the following data. enthalpy of formation of Ag(g) : +284 kJ.mol^-1 First ionization energy of Ag(g) : +731 kJ.mol^-1 Enthalpy of formation of Cl(g) : +122 kJ.mol^-1 Electron affinity of Cl(g) : +349 ( $\Delta$ H = kJ.mol^-1 ) Enthalpy of formation of AgCl(s) : -127 kJ.mol^-1

A reaction known to release 4.00 kJ of heat takes place in a calorimeter containing 0.200 L of solution and the temperature rose by 6.14 ^$\circ$ C.When 200 mL of hydrochloric acid was added to a small piece of calcium carbonate in the same calorimeter,the temperature rose by 4.25 ^$\circ$ C.What is the heat output for this reaction?

The molar heat capacity of a monatomic ideal gas is independent of temperature and pressure.