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Exam 9: Thermochemistry Energy Changes in Chemical Reactions

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Question 1

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The heating curve for a substance is shown below.The substance initially is a solid.It then becomes a liquid and a gas.Which of the line segments (I-V) represents the solid-to-liquid phase transition?

A) I
B) II
C) III
D) IV
E) V

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Question 2

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Calculate the enthalpy of reaction for the conversion of iron(II) oxide in carbon monoxide to iron metal and carbon dioxide using the following reaction information.

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-11 kJ

Question 3

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A gas contained in a cylinder with a movable piston does 485 J of expansion work on the surroundings while gaining 927 J of thermal energy.What is the change in internal energy of the gas?

Which ionic compound below would you expect to have the lowest solubility in water based on its lattice energy?

A 550 g solution at 27.27 $\degree$ C is produced by mixing 0.800 mol hydrocyanic acid with 0.800 mol potassium hydroxide (40.00 g/mol) in water initially at 23.20 $\degree$ C.Calculate the molar enthalpy of neutralization of HCN with KOH.Assume that the heat capacity of the solution is 4.18 J/(g . $\degree$ C) .

For which of the following is the standard enthalpy of formation NOT equal to zero?

Suppose 3.03 kg of asphalt at 58.0 $\degree$ C is quickly transferred to a large water bath containing 10.0 kg of water at 18.0 $\degree$ C.The final equilibrium temperature reached is 20.5 $\degree$ C.What is the heat capacity of asphalt? Assume heat is exchanged only between the water and the asphalt.[c_p,water= 4.18 J/(g . $\degree$ C)]

In an experiment, 30.00 g of aluminum at 98.00 $\degree$ C is added to a calorimeter containing 100.0 g of water at 20.00 $\degree$ C.The final temperature comes to 24.00 $\degree$ C.Calculate the approximate heat capacity of the calorimeter.[c_p of water= 4.18 J/g . $\degree$ C); c_p of Al = 0.897 J/g . $\degree$ C)]

Which of the following does NOT show the reaction associated with the standard heat of formation of a compound?

Coal is converted into cleaner, more transportable fuels by burning it with oxygen to produce carbon monoxide.The carbon monoxide then is reacted with hydrogen using a catalyst to produce methane and water.Is the reaction between CO and H₂ exothermic or endothermic, and what is the change in enthalpy for it? The enthalpies of formation of the reactants and products are given below.

In an experiment, 30.0 g of metal is heated to 98.0 C and then quickly transferred to 50.0 g of water in a calorimeter at 27.0 11eed8b2_2d82_a951_a0ba_55ddc23a4114_TB6562_11 C.The heat capacity of the calorimeter with the water is 211 J/ 11eed8b2_2d82_a951_a0ba_55ddc23a4114_TB6562_11 C.The final temperature comes to 32.5 11eed8b2_2d82_a951_a0ba_55ddc23a4114_TB6562_11 C.What is the approximate specific heat capacity of the metal? [c_p(water) = 4.18 J/(g .11eed8b2_2d82_a951_a0ba_55ddc23a4114_TB6562_11C) ]

An endothermic process is best described as an energy transfer to the _______ from the _______ .

The reaction of sulfur dioxide gas with oxygen to form sulfur trioxide gas at 25 C and 1 atm releases approximately 198.5 kJ of heat while absorbing approximately 2.5 kJ of work.Which of the following is true? 2SO₂ (g) + O₂(g) $\rightarrow$ 2 SO₃(g)

Use the following information to determine the standard enthalpy change when 1 mol of PbOs) is formed from lead metal and oxygen gas.

If steam expands in the cylinder of a steam engine and does 1250 J of work on the surroundings and simultaneously there is 790 J of energy transferred into the steam from the surroundings, what is the change in energy of the steam?

In an experiment, 25.00 g of iron is heated to 228.00 $\degree$ C and then quickly transferred to 100.0 g of water in a calorimeter at 18.00 $\degree$ C.The final temperature comes to 20.50 $\degree$ C.What is the approximate heat capacity of the calorimeter? [c_p(iron) = 0.450 J/(g . $\degree$ C) ; c_p(water) = 4.184 J/(g . $\degree$ C) ]

The cooling system in an automobile holds 10.0 L of ethylene glycol antifreeze.How much energy is absorbed from the engine when the temperature of the ethylene glycol goes from 20.0 $\degree$ C to 100.0 $\degree$ C? The density and specific heat capacity of ethylene glycol are 1.11 g/mL and 2.42 J/(g . $\degree$ C) , respectively.

Given equal masses of the following, which will cool the fastest from the same initial temperature?

Energy that an object has by virtue of its motion is called

The destruction of the ozone layer by chlorofluorocarbons can be described by the following reactions, all occurring in the gas phase. What is $\Delta$ H $\degree$ _rxn for the decomposition of ozone to oxygen?