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Exam 9: Thermochemistry Energy Changes in Chemical Reactions

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Question 21

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Which of the following will require the greatest energy input to separate the ions?

A) BaO
B) MgO
C) CaCl₂
D) MgCl₂
E) CaO

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Question 22

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The combustion of liquefied butane to form carbon dioxide and water vapor occurs according to the reaction below.What is the enthalpy change per mole of CO₂ produced? 2 C₄ H₁₀ (l) + 13O₂ (g) $\rightarrow$ 4 CO₂ (g) +5H₂ O(l) $\Delta$ H =-2707.8 kJ

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Question 23

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Which of the following statements about energy, systems, and surroundings is NOT true?

Which of the following will always increase the internal energy of a system?

Imagine a sample of water vapor at 150 $\degree$ C.List three possible components of a molecule's total kinetic energy.What happens to the average kinetic energy of the molecules if the temperature is doubled?

Which statement below regarding the solubility of molecular compounds in water is FALSE?

Given the following reactions, what is the overall enthalpy change for the following reaction? B₂ O₃ (s) +6 H₂ (g) $\rightarrow$ B₂ H₆ (g) + 3H₂ O(g)

In a steam engine, steam in a cylinder is compressed by a piston exerting 16.5 atm of external pressure.The volume of the cylinder decreases by 22.4 L, and simultaneously the steam heats up.If the total energy change of the steam is 42.6 kJ, calculate the heat flow into/out of the steam. (101.3 J =1 L.atm)

If a chemical reaction causes the temperature of the reaction vessel to decrease, it is (an) _______ reaction.

How much energy is needed to change the temperature of 25.00 mL of water from 10.0 $\degree$ C to 95.0 $\degree$ C? [c_p= 4.18 J/(g . $\degree$ C) , d =1.00 g/mL]

Determine the energy change for the reaction $\mathrm{Li}(s) +1 / 2 \mathrm{Cl}_{2}(g) \rightarrow \operatorname{LiCl}(s)$ from the following data: Lattice energy of LiCl = -861 kJ/mol Energy to vaporize Li = 159 kJ/mol Ionization energy of Li = 520 kJ/mol Cl₂ bond energy: 240 kJ/mol Electron affinity of Cl: -349 kJ/mol

Which of the ionic compounds below would you expect to have the smallest least negative) lattice energy?

Briefly explain how bond energies can be used to estimate reaction enthalpies.

Which of the following requires the smallest energy to separate the ions?

Given the following reactions, what is the overall enthalpy change for the following reaction? NH₃ (g) + HCl(g) $\rightarrow$ NH₄ Cl(s)

Ammonium nitrate 80.04 g/mol) decomposes at high temperatures to form nitrogen, oxygen, and water vapor.Suppose 750 grams decomposes at 350 $\degree$ C and 0.98 atm, generating gases that expand by about 960 L.How much P-V work is done? What is the approximate change in internal energy ( $\Delta$ E ) of the reaction system? (1 L. atm =101.3 J) NH₄ NO₃ (s) $\rightarrow$ N₂ (g)+ 1/ 2 O₂ (g) + 2H₂ O(g) $\Delta$ H =- 118 kJ/mol

In an experiment, 15.0 cm³ of glucose (C₆H₁₂O₆, 180.2 g/mol, 1.54 g/cm³) undergoes combustion to form carbon dioxide and water.The energy released is completely transferred to 1150 grams of water [c_p = 1.00cal/g . $\degree$ C], which then experiences a temperature increase of 74.9 $\degree$ C.What is the food value Cal/g) of glucose? (1 Cal . 4.184 kJ)

A 7.50 g marshmallow is placed in a calorimeter and burned in excess oxygen.The temperature increases by 4.69 $\degree$ C.The calorimeter has a heat capacity of 22.3 kJ/ $\degree$ C.What is the approximate food value of marshmallows in Cal/g? (1 Cal = 4.184 kJ)

Which of the following is needed to calculate the lattice energy of an ionic compound?

In an experiment, 24.0 grams of ice at -20.0C are converted to steam at 140.011eed8b6_0382_1c43_a0ba_2fe0925836f4_TB6562_11C.About how many kilojoules of energy are required for this process? $\Delta$ H_vap =2260 J/g; $\Delta$ H_fus =334 J/g; c_p(ice) = 2.06 J/(g .11eed8b6_4681_e7a4_a0ba_0b26d50616e5_TB6562_11C); c_p(water) = 4.18 J/(g .11eed8b6_4681_e7a4_a0ba_0b26d50616e5_TB6562_11C);c_p(steam) =1.99 J/(g .11eed8b6_4681_e7a4_a0ba_0b26d50616e5_TB6562_11C)]