Chemistry Straighterline

A piece of copper with a mass of 218 g has a heat capacity of 83.9 J/oC. What is the specific heat of copper? A. 0.385 J/g•oC B. 1.83 ´ 104 J/g•oC C. 2.60 J/g•oC D. 1.32 J/g•oC E. 24.5 J/g•oC

A

The heat of neutralization of HCl by NaOH is given below: HCl(aq) + NaOH(aq) NaCl(aq) + H2O(l) ΔHorxn = ─56.2 kJ/mol How much heat is released when 125 mL of 1.750 M HCl is mixed with 195 mL of 0.667 M NaOH?

Answer: 7.31 kJ

How many grams of ethylene (C2H4) would have to be burned to produce 450 kJ of heat? C2H4 + 3O2 2CO2 + H2O ΔHorxn= ─1411 kJ

Answer: 8.95 g

Define exothermic process

Answer: Any process that gives off heat to the surroundings.

Define endothermic process.

Answer: Any process that takes in heat from the surroundings.

What is the ΔHorxn for the reaction. CH4(g) + 2O2(g) CO2(g) + 2H2O(l) ΔHof CH4(g) = ─74.8 kJ; ΔHof CO2(g) = ─393.5 kJ; ΔHof H2O(l) = ─285.5 kJ

Answer: ─889.7 kJ

Given the thermochemical equation: 2SO2(g) + O2(g) 2SO3(g) ΔHorxn= ─198 kJ How much heat is evolved when 600 g of SO2 is burned? A. 5.46 10 ─ 2 kJ B. 928 kJ C. 1.85 103 kJ D. 59,400 kJ E. 3.71 103 kJ

B

Which one of the following reactions occurring at 25oC does the symbol ΔHof[H2SO4(l)] refer to? A. 2H(g) + S(g) + 4O(g) H2SO4(l) B. H2(g) + S(g) + 2O2(g) H2SO4(l) C. H2SO4(l) H2(g) + S(s) + 2O2(g) D. H2SO4(l) 2H(g) + S(s) + 4O(g) E. H2(g) + S(s) + 2O2(g) H2SO4(l)

E

Chemical reactions in a bomb calorimeter occur at constant pressure Conditions.

FALSE

The specific heats of water and iron are 4.184 and 0.444 J/g•oC, respectively. When equal masses of water and iron both absorb the same amount of heat, the temperature increase of the water will be 5.42 times greater than that of the iron.

FALSE

A home aquarium is an example of an open system

TRUE

If 2Mg(s) + O2(g) 2MgO(s) ΔHo = ─1203.6 kJ; then for Mg(s) + 1/2O2(g) MgO(s) the enthalpy change is ΔHf = ─601.8 kJ

TRUE

In an endothermic process heat is absorbed by the system.

TRUE

The heat absorbed by a system at constant pressure is equal to ΔE + PΔV.

TRUE

The heat capacity of 20.0 g of water is 83.7 J/oC.

TRUE

The work done on the surroundings by the expansion of a gas is w = ─PΔV.

TRUE

A calorimeter temperature increases by 0.45°C when 30 J of energy is added to it by electrical heating. When 0.10 grams of HCl is neutralized in the same calorimeter, the temperature increased by 7.3°C. What is the ΔH of neutralization of HCl in units of kJ/mol? A. ─177 kJ/mol B. 0.486 kJ/mol C. 1.8 102 kJ/mol D. ─486 kJ/mol 177 kJ/mol

A

A gas is allowed to expand at constant temperature from a volume of 1.0 L to 10.1 L against an external pressure of 0.50 atm. If the gas absorbs 250 J of heat from the surroundings, what are the values of q, w, and ΔE? q w ΔE A. 250 J ─460 J ─210 J B. ─250 J ─460 J ─710 J C. 250 J 460 J 710 J D. ─250 J 460 J 210 J E. 250 J ─4.55 J 245 J

A

An exothermic reaction causes the surroundings to: A. warm up B. become acidic C. expand D. decrease its temperature E. release CO2

A

Find the standard enthalpy of formation of ethylene, C2H4(g), given the following data: C2H4(g) + 3O2(g) 2CO2(g) + 2H2O(l) ΔHof = ─1411 kJ C(s) + O2(g) CO2(g) ΔHof = ─393.5 kJ H2(g) + 1/2O2(g) H2O(l) ΔHof = ─285.8 kJ A. 52 kJ B. 87 kJ C. 731 kJ D. 1.41 103 kJ E. 2.77 103 kJ

A

Given 2Al(s) + 3/2O2(g) Al2O3(s) ΔHof = ─1670 kJ What is ΔH for the reaction? 2Al2O3(s) 4Al(s) + 3O2(g) ΔHorxn = ? A. 3340 kJ B. 1670 kJ C. ─3340 kJ D. ─1670 kJ E. ─835 kJ

A

Given that: 2 H2(g) + O2(g) 2 H2O(l); ΔH° = ─571 kJ/mol C3H4(g) + 4 O2(g) 3 CO2(g) + 2 H2O(l); ΔH° = ─1941 kJ/mol C3H8(g) + 5 O2(g) 3 CO2(g) + 4 H2O(l); ΔH° = ─2220 kJ/mol Calculate the ΔH° value for the reaction C3H4(g) + 2 H2(g) C3H8(g) A. ─292 kJ/mol B. +292 kJ/mol C. +850 kJ/mol ─850 kJ/mol

A

Glycine C2H5O2N is important for biological energy. The combustion of glycine is given by the equation, 4C2H5O2N(s) + 9O2(g) 8CO2(g) + 10H2O(l) + 2N2(g) ΔHorxn = ─3857 kJ Given that ΔHof[CO2(g)] = ─393.5 kJ/mol, and ΔHof[H2O(l)] = ─285.8 kJ/mol. Calculate the enthalpy of formation ΔHof per mole of glycine. A. ─537.2 kJ/mol B. ─268.2 kJ/mol C. 2149 kJ/mol D. ─3178 kJ/mol E. ─964 kJ/mol

A

How much heat is absorbed in the complete reaction of 3.00 grams of SiO2 with excess carbon in the reaction below? ΔH° for the reaction as written is +624.7 kJ. SiO2(g) + 3C(s) SiC(s) + 2 CO(g) A. 31.2 kJ B. 1.13 105 kJ C. 5.06 kJ D. 1.33 104 kJ E. 366 kJ

A

Octane (C8H18) undergoes combustion according to the following thermochemical equation: 2C8H18(l) + 25O2(g) 16CO2(g) + 18H2O(l) ΔHorxn = ─11,020 kJ. Given that: ΔHof[CO2(g)] = ─393.5 kJ/mol ΔHof[H2O(l)] = ─285.8 kJ/mol Calculate the enthalpy of formation of 1 mole of octane. A. ─210 kJ B. ─11,230 kJ C. 22,040 kJ D. ─420 kJ E. 420 kJ

A

If we have 75 g of water at 25oC to boil to dryness: a. How much heat is added to the water to raise the temperature to 100oC? b. How much heat is added to evaporate the water? c. What is the total amount of heat used? Heat of fusion of water = 335 J/g Specific heat of water = 4.189 J/g•oC Heat of vaporization = 2262 J/g

Answer: a. 24 kJ b. 170 kJ c. 190 kJ

The combustion of one mole of benzene, C6H6, in oxygen liberates 3268 kJ of heat. The products of the reaction are carbon dioxide and water. a. Write the thermochemical equation for the combustion of benzene. b. Is the reaction exothermic or endothermic? c. How much heat is given off when 8 moles of benzene are burned? d. How much heat is given off when 183 gms of oxygen are reacted?

Answer: a. 2C6H6(l) + 15O2(g) 12CO2(g) + 6H2O(g) + 6536 kJ b. exothermic c. 26,140 kJ d. 2490 kJ

Ice cubes are made by taking heat away from water. If you put 500 g of 20oC water in an ice tray and put it into the freezer: a. How many joules of heat must be removed to cool the water to 0oC? b. How many joules of heat must be removed to change water from liquid to solid? c. What is the total heat removed? Heat of fusion of water = 335 J/g Specific heat of water = 4.189 J/g•oC Heat of vaporization = 2262 J/g

Answer: a. 41.9 kJ b. 168 kJ c. 209 kJ

What is the standard enthalpy of formation of H2(g) ?

Answer: 0 kJ

The heat released when one mole of water is formed from the elements is 1198 kJ. An experiment was conducted that permitted water to form in this manner, and the heat was contained in 2.0 liters of water. The water temperature before the reaction was 34.5oC, and after the reaction it had risen to 52.0oC. How many moles of water were formed? The specific heat of water is 4.184 J/g•oC

Answer: 0.12 moles

A 26.2 g piece of copper metal is heated from 21.5oC to 201.6oC. Calculate the heat absorbed by the metal. The specific heat of Cu is 0.385 J/g •oC.

Answer: 1820 J

The enthalpy of combustion of acetylene C2H2 is C2H2(g) + 5/2O2(g) 2CO2(g) + H2O(l) ΔHorxn= ─1299 kJ Calculate the enthalpy of formation of acetylene, given the following enthalpies of formation ΔHof[CO2(g)] = ─393.5 kJ/mol ΔHof[H2O(l)] = ─285.8 kJ/mol

Answer: 227 kJ

A 0.1946 g piece of magnesium metal is burned in a constant volume calorimeter that has a heat capacity of 1349 J/oC. The calorimeter contains 500 g of water and the temperature rise is 1.40oC. Calculate the heat of combustion of magnesium metal in kJ/g.

Answer: 24.8 kJ/g

The specific heat of silver is 0.235 J/g for each degree celsius change in temperature. How many joules of heat are required to heat a 75 g silver spoon from 20oC to 35oC?

Answer: 260 J

Thunderstorms are powered by changing water vapor to rain drops. How much heat is released when a gallon of water falls? 1 gal = 1816 g

Answer: 4,108 kJ

A feverish student weighing 75 kilograms was immersed in 400 kg of water at 4.0oC to try to reduce the fever. The student's temperature dropped from 40oC to 37oC. Assuming the specific heat of the student to be 3.77 J/g•oC, what was the final temperature of the water?

Answer: 4.5oC

What is the ΔHrxn for the reaction. 2Ag2S(s) + 2H2O(l) 4Ag(s) + 2H2S(g) + O2(g) ΔHof Ag2S(s) = ─32.6 kJ; ΔHof H2S(g) = ─20.5 kJ; ΔHof H2O(l) = ─285.5 kJ

Answer: 595.2 kJ

At body temperature it requires 2404 joules to evaporate 1 g of water. After vigorous exercise a person feels chilly because their body is giving up heat to evaporate the perspiration. A typical person perspires 25 mL of water after 20 minutes of exercise. How much body heat is this person using to evaporate this water?

Answer: 60,100 J

When an automobile engine starts, the metal parts immediately begin to absorb heat released during the combustion of gasoline. How much heat will be absorbed by a 165 kg iron engine block when the temperature rises from 15.7oC to 95.7oC? The specific heat of iron is 0.489 J/g•oC.

Answer: 6450 kJ

The value of ΔHorxn for the following reaction is -6535 kJ. How many kJ of heat will be evolved during the combustion of 16.0 g of C6H6(l)? 2C6H6(l) + 15O2(g) 12CO2(g) + 6H2O(g)

Answer: 670 kJ

Define specific heat

Answer: The amount of heat required to raise the temperature of one gram of the substance by one degree Celsius.

Measuring Heat of Reaction for a simple system An important thermodynamic property in a reaction is the molar enthalpy of reaction (qsys). The molar enthalpy of reaction is defined as the heat absorbed by the system from the surroundings in a reaction when one mole of product is formed. If the reaction is carried out in aqueous solution, the heat liberated or absorbed by the system can be calculated by measuring the temperature change of the surroundings - the water - by using the formula: qw = (mass)w (Specific Heat)w (Δt)w The heat change of the system (qsys) will be the same value but opposite in sign. This value is the amount of heat actually liberated in the experiment, it is not the molar heat of reaction! (qsys) To find the molar heat of reaction, the quantity of one of the products must be found. (Not the total moles of the product, just the moles of one of the product; e.g. the moles of water formed.) The molar heat of reaction then would be the heat released during the experiment divided by the moles of water formed. Working in a general chemistry lab, you perform the following experiment: Measure the initial temperature of each of the following solutions as accurately as possible. Record these temperatures. Pour exactly 50 mL of the 2.0 M NaOH into a clean, dry, styrofoam cup. Add exactly 50 mL of the 2.0 M HCl and stir gently with a thermometer. Record the highest reading observed on the thermometer. Since the solutions are diluted, or mostly water, the total amount of water present in the cup will be assumed to be exactly 100 mL. Specific heat of water = 4.184 J/g•oC You obtain the following data. a. Initial temperature of NaOH: 20oC b. Initial temperature of HCl: 20oC c. Final temperature of NaOH + HCl: 33oC d. Total volume of water in the reaction vessel: 100 mL Answer the following questions (show your work) a. Temperature change (ΔT) in reaction 1 ? b. Heat absorbed by the water in reaction 1 ? c. How much heat was liberated in the reaction ? d. How many moles of product were formed in the reaction? (stoichiometry) e. How much heat was liberated per mole of product? (ΔHorxn)

Answer: a. 13oC, b. 5446 J, c. 5446 J, d. 0.1 mole, e. 54,460 J/mol

A 0.3423 g sample of pentane, C5H12, was burned in a bomb calorimeter. The temperature of the calorimeter and the 1 kg of water rose from 20.22oC to 22.82oC. The heat capacity of the calorimeter is 2.21 kJ/oC. a. How much heat was given off during combustion of the sample of pentane? b. What is the heat of combustion per gram of pentane? c. What is the heat of combustion per mole of pentane?

Answer: a. 16.6 kJ b. 48.6 kJ c. 3.50 MJ

Calculate the enthalpy of reaction for H2(g) + C2H4(g) C2H6(g) ΔHorxn = ? Given the following standard enthalpies of formation at 25oC. ΔHof[C2H4(g)] = 52.3 kJ/mol ΔHof[C2H6(g)] = ─84.7 kJ/mol

Answer: ─137 kJ

What would be the standard enthalpy change for the reaction of one mole of H2(g) with one mole of Cl2(g) to produce two moles of HCl(g) at standard at standard state conditions? ΔHof = ─92.3 kJ; H2(g) + Cl2(g) 2HCl(g)

Answer: ─184.6 kJ

What is the ΔHrxn for the reaction. 2Na(s) + 2H2O(l) 2NaOH(s) + 2H2(g) ΔHof NaOH(s) = ─426.8 kJ; ΔHof H2O(l) = ─285.5 kJ

Answer: ─282.6 kJ

Given the following ΔH values H2(g) + 1/2O2(g) H2O(l) ΔHof = ─285.8 kJ H2O2(l) H2(g) + O2(g) ΔHrxn = 187.6 kJ Calculate ΔHrxn for the following reaction H2O2(l) H2O(l) + 1/2O2(g)

Answer: ─98.2 kJ

10.1 g CaO is dropped into a styrofoam coffee cup containing 157 g H2O at 18.0oC. If the following reaction occurs, then what temperature will the water reach assuming that the cup is a perfect insulator and that the cup absorbs only a negligible amount of heat? CaO(s) + H2O(l) Ca(OH)2(s) ΔHorxn = ─64.8 kJ/mol A. 18.02oC B. 35.8oC C. 311oC D. 42.2oC E. 117oC

B

An average home in Colorado requires 20 GJ of heat per month. How many grams of natural gas as methane must be burned to supply this energy? CH4(g) + 2O2(g) CO2(g) + 2H2O(l) ΔHorxn= ─890.4 kJ A. 1.4 103 g B. 3.6 105 g C. 7.1 10-4 g D. 2.2 104 g E. 1.4 104 g

B

Calcium oxide and water react in an exothermic reaction. CaO(s) + H2O(l) Ca(OH)2(s) ΔHorxn = ─64.8 kJ/mol How much heat would be liberated when 7.15 g CaO(s) is dropped into a beaker containing 152 g H2O. A. 1.97 kJ B. 8.26 kJ C. 508 kJ D. 547 kJ E. 555 kJ

B

Calculate the enthalpy change for the reaction: C(graph) + 2H2(g) + 1/2O2(g) CH3OH(l) Using the following information: C(graph) + O2 CO2(g) ΔHof = ─393.5 kJ. H2(g) + 1/2O2 H2O(l) ΔHof = ─285.8 kJ. CH3OH(l) + 3/2O2(g) CO2(g) + 2H2O(l) ΔHorxn = ─726.4 kJ A. ─1691.5 kJ B. ─238.7 kJ C. 1691.5 kJ D. 47.1 kJ E. ─47.1 kJ

B

Calculate the enthalpy change for the reaction: 2C8H18(l) + 21O2(g) 8CO(g) + 8CO2(g) + 18H2O(l) ΔHorxn = ? Given: 2C8H18(l) + 25O2(g) 16CO2(g) + 18H2O(l) ΔHorxn = ─11,020 kJ. 2CO(g) + O2(g) 2CO2(g) ΔHof = ─566.0 kJ. A. 1.0454 104 kJ B. ─8756 kJ C. 1.1586 104 kJ D. ─6,492 kJ E. ─1.0454 104 kJ

B

Calculate the work done in joules when 2.5 mol of H2O vaporizes at 1.0 atm and 25oC. Assume the volume of liquid H2O is negligible compared to that of vapor. Given 1 L•atm = 101.3 J. A. 6190 kJ B. 6.19 kJ C. 61.1 J D. 5.66 kJ E. 518 J

B

Calculate the ΔH° of the following reaction: C2H4(g) + H2(g) C2H6(l) Given the standard enthalpies of formation of the following species: Substance ΔH°f --------------------------------- C2H4(g) +52.3 kJ C2H6(l) ─84.86kJ A. +137.2 kJ B. ─137.2 kJ C. +32.6 kJ ─32.6 kJ

B

Ethanol fuel (C2H5OH) burns according to the equation below. How much heat is released when 35.0 g of ethanol is burned? C2H5OH(l) + 3O2(g) 2CO2(g) + 3H2O(l) ΔHorxn = ─1367 kJ A. ─1797 kJ B. ─1040 kJ C. ─9.61 kJ D. ─4.78 104 kJ E. ─1367 kJ

B

Given the standard heats of formation for the following compounds, calculate the ΔH° heat of reaction, for the following reaction: Fe3O4(s) + CO(g) 3 FeO(s) + CO2(g) ΔHf° for Fe3O4 = ─1118 kJ ΔHf° for CO = ─110.5 kJ ΔHf° for FeO = ─272 kJ ΔHf° for CO2 = ─393.5 kJ A. 54 kJ B. 19 kJ C. ─263 kJ D. ─50 kJ 109 kJ

B

How much heat is absorbed from the surroundings when 15 g of O2 react according to the equation? O + O2 O3 ΔHorxn= 103 kJ A. 4.6 kJ B. 48 kJ C. 96 kJ D. 32 kJ E. 110 kJ

B

How much heat is required to raise the temperature of 1500 g of water from 25oC to 52oC? A. 1500 kJ B. 169 kJ C. 6.27 kJ D. 40.5 J E. 40.5 kJ

B

Methanol fuel (CH3OH) burns according to the equation below. How much heat is given off when 75.0 g of H methanol is burned? 2CH3OH(l) + 3O2(g) 2CO2(g) + 4H2O(l) ΔHorxn = ─1454 kJ A. 727 kJ B. 1.70 103 kJ C. 1.45 103 kJ D. 3.22 10 ─ 3 kJ E. 3.41 103 kJ

B

Pentaborane B5H9(s) burns vigorously in O2 to give B2O3(s) and H2O(l). Write and balance the combustion equation. Calculate the ΔHorxn for the combustion of 1 mol of B5H9 given the following enthalpies of formation. ΔHof[B2O3(s)] = ─1273.5 kJ/mol ΔHof[B5H9(s)] = 73.2 kJ/mol ΔHof[H2O(l)] = ─285.8 kJ/mol A. ─1.2735 MJ B. ─4.543 MJ C. ─18.170 MJ D. ─9.086 MJ E. ─8.448 MJ

B

The combustion of butane produces heat according to the equation: 2C4H10(g) + 13O2(g) 8CO2(g) + 10H2O(l) ΔHorxn= ─5314 kJ How many grams of butane must be burned to release 6375 kJ of heat? A. 1.20 g B. 139 g C. 0.0413 g D. 69.7 g E. 97.8 g

B

The combustion of butane produces heat according to the equation: 2C4H10(g) + 13O2(g) 8CO2(g) + 10H2O(l) ΔHorxn = ─5,314 kJ What is the heat of combustion per gram of butane? A. -32.5 kJ B. -45.7 kJ C. -91.5 kJ D. -2,656 kJ E. -15,440 kJ

B

The number of resonance structures for the sulfur dioxide molecule that satisfy the octet rule is a. 1. B. 2. c. 3. d. 4. e. none of these

B

Use the Born-Haber cycle to calculate the lattice energy of NaBr (s) given the following data: H(sublimation) Na = 177.8 kJ/mol I1 (Na) = 495.9 kJ/mol Bond energy (Br-Br) = 192.5 kJ/mol EA (Br) = 325 kJ/mol Hf (NaBr(s)) = -361.1 kJ/mol a. 1456 kJ/mol B. 806 kJ/mol c. 450 kJ/mol d. 902 kJ/mol e. 421 kJ/mol

B

Which one of the following reactions occurring at 25oC does the symbol ΔHof[HNO3(l)] refer to? A. H(g) + N(g) + O3(g) HNO3(l) B. 1/2H2(g) + 1/2N2(g) + 3/2O2(g) HNO3(l) C. HNO3(l) 1/2H2(g) + 1/2N2(g) + 3/2O2(g) D. HNO3(l) H(g) + N(g) + 3O(g) E. H2(g) + N2(g) + O3(g) HNO3(l)

B

A gas is compressed in a cylinder by a constant pressure of 10 atm from a volume H of 20 L to 2.0 L. Calculate the work done on the system. A. 1.01 104 J B. -180 J C. 1.81 104 J D. ─1.81 104 J E. 180 J

C

A glass containing 200 g of H2O at 20oC was placed into a refrigerator. The water loses 11.7 kJ as it cools to a constant temperature. What is its new temperature? A. 0.013oC B. 4oC C. 6oC D. 14oC E. 34oC

C

According to the first law of thermodynamics: A. Energy is neither lost nor gained in any energy transformations. B. Perpetual motion is possible. C. Energy in a closed system is conserved. D. Energy is being created as time passes. We have more energy in the universe now than when time began.

C

Ethanol undergoes combustion according to the equation: C2H5OH(l) + O2(g) CO2(g) + H2O(l) (Not Balanced) The standard heat of combustion of ethanol, C2H5OH(l), is ─1366.8 kJ/mol. Given that: ΔHof[CO2(g)] = ─393.5 kJ/mol ΔHof[H2O(l)] = ─285.8 kJ/mol What is the standard enthalpy of formation of ethanol? A. 3010 kJ B. ─687.6 kJ C. ─277.6 kJ D. 687.6 kJ E. 1367 kJ

C

Given the following information: CaO(s) + H2O(l) Ca(OH)2(s) ΔHorxn = ─64.8 kJ/mol How many grams of CaO must react in order to liberate 525 kJ of heat? A. 6.92 g B. 56.1 g C. 455 g D. 606 g E. 3.40 104 g

C

Given the thermochemical equation: 2SO2 + O2 2SO3 ΔHorxn = ─198 kJ. What is the enthalpy change (ΔHo) for the decomposition of one mole of SO3? A. 198 kJ B. ─99 kJ C. 99 kJ D. 396 kJ E. ─198 kJ

C

How much heat is given off to the surroundings when 9.0 g of aluminum react according to the equation? 2Al + Fe2O3 Al2O3 + 2Fe ΔHorxn= ─849 kJ A. 7.6 103 kJ B. 2.8 102 kJ C. 1.4 102 kJ D. 5.6 102 kJ E. 2.5 103 kJ

C

Naphthalene combustion can be used to determine the heat capacity of a bomb calorimeter. The heat of combustion of naphthalene is 40.1 kJ/g. When 0.8210 g of naphthalene was combusted in a calorimeter containing 1000 g of water a temperature rise of 4.21oC was observed. What is the heat capacity of the bomb calorimeter excluding the water? A. 32.9 kJ/oC B. 7.8 kJ/oC C. 1.76 kJ/oC D. 1.76 kJ/oC E. 15.3 kJ/oC

C

The combustion of octane produces heat according to the equation: 2C8H18(l) + 25O2(g) 16CO2(g) + 18H2O(l) ΔHorxn= ─11,020 kJ What is the heat of combustion per gram of octane? A. 5.510 MJ B. 96.5 kJ C. 48.2 kJ D. 193 kJ E. 629.2 MJ

C

The number of resonance structures for the nitrate ion that satisfies the octet rule is a. 1. b. 2. C. 3. d. 4. e. none of these.

C

The specific heat of gold is 0.129 J/g•oC. What is the molar heat capacity of gold (unit is J/mol•oC)? A. 0.039 J/mol•oC B. 0.129 J/mol•oC C. 25.4 J/mol•oC D. 39.0 kJ/mol•oC E. 197 J/mol•oC

C

6.52 The standard enthalpy of formation of glucose, C6H12O6 (s) refers to the ΔH° of which reaction below? 6 CO2(g) + 6 H2O(l) C6H12O6(s) + 6 O2(g) A) A6 CO2(g) + 6 H2O(g) C6H12O6(s) B) BC6H12O6(s) 6 C(graphite) + 3 O2(g) + 6 H2(g) C) C6 C(graphite)) + 3 O2(g) + 6 H2(g) C6H12O6(s) D) DC6H12O6(s) + 6 O2(g) 6 CO2(g) + 6 H2O(1)

D

An endothermic reaction causes the surroundings to: A. warm up B. become acidic C. condense D. decrease in temperature E. release CO2

D

Calculate the enthalpy change for the reaction: 2C8H18(l) + 17O2(g) 16CO(g) + 18H2O(l) ΔHorxn = ? Given: 2C8H18(l) + 25O2(g) 16CO2(g) + 18H2O(l) ΔHorxn = ─11,020 kJ. 2CO(g) + O2(g) 2CO2(g) ΔHof = ─566.0 kJ. A. 10.450 MJ B. 6.492 MJ C. 15.550 MJ D. ─6.492 MJ E. ─10.450 MJ

D

Copper metal has a specific heat of 0.385 J/g•oC and has a melting point of 1083oC. calculate the amount of heat required to raise the temperature of 22.8 g of Cu from 20.0oC to 875oC. A. 1.97 10 ─ 5 J B. 1.0 10 ─ 2 J C. 329 J D. 7.51 kJ E. 10.5 kJ

D

From the following data at 25°C: H2(g) + Cl2 2 HCl(g); ΔH° = ─185 kJ 2 H2(g) + O2(g) 2 H2O(g); ΔH° = ─483.7 kJ Calculate ΔH° at 25° for the reaction below: 4 HCl(g) + O2(g) 2 Cl2(g) + 2 H2O(g) A. +114 kJ B. +299 kJ C. ─299 kJ D. ─114 kJ E. ─86.8 kJ

D

Given that: 2 SO3(g) 2 SO2(g) + O2(g); ΔHorxn = +197.8 kJ/mol S(s) + (3/2) O2(g) SO3(g); ΔHorxn = ─395.7 kJ/mol Determine the heat of formation for SO2. A. + 98.9 kJ/mol B. + 197.8 kJ/mol C. +691.8 kJ/mol ─296.8 kJ/mol

D

Given: H2(g) + 1/2O2(g) H2O(l) ΔHof = ─286 kJ What is the enthalpy change for the following reaction? 2H2O(l) 2H2(g) + O2(g) ΔHorxn = ? A. ΔHo = ─286 kJ B. ΔHo = +286 kJ C. ΔHo = ─572 kJ D. ΔHo = +572 kJ E. ΔHo = ─143 kJ

D

If 325 g of water at 4.2oC absorbs 12.28 kJ, then what is the final temperature of the water? A. 4.21oC B. 4.8oC C. 9.0oC D. 13.2oC E. 2938oC

D

The Lewis structure for a chlorate ion, ClO3-, should show ____ single bond(s), ____ double bond(s), and ____ lone pair(s). a. 2, 1, 10 b. 3, 0, 9 c. 2, 1, 8 D. 3, 0, 10 e. 2, 1, 9

D

The combustion of pentane produces heat according to the equation: C5H12(l) + 8O2(g) 5CO2(g) + 6H2O(l) ΔHorxn= ─3510 kJ How many grams of CO2 are produced per 2500 kJ of heat released? A. 0.0809 g B. 3.56 g C. 31.3 g D. 157 g E. 309 g

D

Use the Born-Haber cycle to calculate the lattice energy of LiCl(s) given the following data: H(sublimation) Li = 155.2 kJ/mol I1 (Li) = 520 kJ/mol Bond energy (Cl-Cl) = 242.8 kJ/mol EA (Cl) = 348 kJ/mol Hf (LiCl(s)) = -408.8 kJ/mol a. -40 kJ/mol b. 40 kJ/mol c. 736 kJ/mol D. 857 kJ/mol e. 1,553 kJ/mol

D

When 0.7521 g of benzoic acid was burned in a calorimeter containing 1000 g of water, a temperature rise of 3.60oC was observed. What is the heat capacity of the bomb calorimeter, excluding water? The heat of combustion of benzoic acid is ─26.42 kJ/g. A. 15.87 kJ/oC B. 4.18 kJ/oC C. 5.52 kJ/oC D. 1.34 kJ/oC E. 752.1 kJ/oC

D

Which of the following processes is endothermic? a. O2(g) + 2H2(g) 2H2O(g) b. H2O(g) H2O(l) c. 3O2(g) + 2CH3OH(g) 2CO2(g) + 2H2O(g) d. H2O(s) H2O(l)

D

A 0.1326 g sample of magnesium was burned in an oxygen bomb calorimeter. The Htotal heat capacity of the calorimeter plus water was 5760 J/oC. If the temperature rise of the calorimeter with water was 0.570oC, calculate the enthalpy of combustion of magnesium. Mg(s) + 1/2O2(g) MgO(s) A. ─3280 kJ/mol B. ─24.8 kJ/mol C. 435 kJ/mol D. 106 kJ/mol E. ─602 kJ/mol

E

A 100 mL sample of 0.200 M aqueous hydrochloric acid is added to 100 mL of 0.200 M aqueous ammonia in a calorimeter whose heat capacity is 480 J K ─ 1. The following reaction occurs when the two solutions are mixed. HCl(aq) + NH3(aq) NH4Cl(aq) The temperature increase is 2.34oC. Calculate ΔH per mole of HCl neutralized. A. 154 kJ B. 44.5 kJ C. 22.5 kJ D. ─22.5 kJ E. ─56.2 kJ

E

Calculate the amount of heat necessary to raise the temperature of 12.0 kg of water from 15.4oC to 93.0oC. A. 0.027 kJ B. 324 kJ C. 389 kJ D. 931 kJ E. 3890 kJ

E

Calculate the work done against an atmospheric pressure of 1.00 atm when 500.0 g of zinc dissolves in excess acid at 30.0oC. Zn(s) + 2H+(aq) Zn2+(aq) + H2(g) A. w = +22.4 kJ B. w = +24.9 kJ C. w = 0 D. w = ─2.52 kJ E. w = ─19.3 kJ

E

Calculate ΔHorxn for the following reaction. 2H2O2(l) 2H2O(l) + O2(g) Use the following information: ΔHof (H2O2(l)) = -187.6 kJ/mol ; ΔHof (H2O(l)) = -285.8 kJ/mol ; ΔHof (O2(g)) = 0 kJ/mol A. 53.0 kJ B. 98.2 kJ C. -98.2 kJ D. 196.4 kJ E. ─196.4 kJ

E

For the reaction: C(s) + O2(g) CO2(g) ΔHof = ─393 kJ How many grams of C(s) must be burned to release 275 kJ of heat? A. 22.3 g B. 0.70 g C. 12.0 g D. 17.1 g E. 8.40 g

E

Given that: S(s) + O2(g) SO2(g); ΔH = ─296.8 kJ/mol 2 SO3(g) 2 SO2(g) + O2(g); ΔH = +197.8 kJ/mol Determine the enthalpy change of the reaction: 2 S(s) + 3O2(g) 2 SO3(g) A. ─99 kJ/mol B. 99 kJ/mol C. 495 kJ/mol D. ─495 kJ/mol ─791.4 kJ/mol

E

How many degrees of temperature rise will occur when a 25.0 g block of aluminum absorbs 10 kJ of heat? The specific heat of Al is 0.900 J/g•oC. A. 0.44oC B. 22.5oC C. 225oC D. 360oC E. 444oC

E

The combustion of butane produces heat according to the equation: 2C4H10(g) + 13O2(g) 8CO2(g) + 10H2O(l) ΔHorxn= ─5314 kJ How many grams of CO2 are produced per 1.00 104 kJ of heat? A. 23.4 g B. 44.0 g C. 82.3 g D. 187 g E. 662 g

E

The ΔH° of the combustion for methane CH4, is ─890 kJ/mole. How many kg of methane must be burned to supply a house with 2.0 105 kJ daily requirement of energy? A. A2.97 kg B. B535 g C. C60.6 g D. D2.97 g E 3.6 kg

E

When 0.56 g of Na(s) react with excess F2(g) to form NaF(s) at standard state conditions, 13.8 kJ of heat are evolved. What is the standard enthalpy of formation (ΔHof) of NaF(s)? A. 24.8 kJ/mol B. +570 kJ/mol C. ─24.8 kJ/mol D. ─7.8 kJ/mol E. ─570 kJ/mol

E