Energetics Questions and Answers

Consider the reaction A 2B C SO A 131 26 J molk So B 234 54 J molk S C 192 38 J molk Determine the entropy change of the reaction at 298 K in J Do not report units in your answer Report your answer with 2 places past the decimal point Incorrect sign won t receive points Type your answer

A 0 853 mol sample of liquid propanol 60 09 g mol is heated from 25 1 C to 323 5 C The boiling point of propanol is 206 6 C The specific heat of liquid propanol is 2 4 J g C The specific heat of propanol vapor is 1 42 J g C The enthalpy of vaporization for propanol is 47 5 kJ mol What is the energy change of this process in kJ Do not report units in your answer Report your answer with 1 place past the decimal point Type your answer

Consider the equation 2A 3B 2C AGO A 52 64 kJ mol AGO B 184 63 kJ mol AGO C 49 22kJ mol Calcualte AGO for this reaction at 298K in kJ Report your answer with 2 places past the decimal point Type your answer

For the reaction A B C at 25 C the standard enthalpy is 10 0 kJ mol and the standard entropy is 2 00 J mol K What is the standard free energy change

How much heat does it take to warm 16 0 g of pure water from 90 0 C to 100 0 C Q mxcx4T specific heat of water 4 184 J g C 669 J 160 J 669 I

The temperature of a 6 0 g sample of glass changed from 20 C to 45 C when it absorbed 550 J of heat What is the specific heat of this glas sample in J g C Q mxcx4T 0 27 J g C 2300 J g C 3 7 J g C 130 J g C

Examine the graph below Which of the following statements describing the diagram is TRUE Energy Reactants AH Activation Energy Reaction Products energy is being absorbed this is an exothermic reaction the reactants have less energy than the products this is an endothermic reaction

Elements Lead Gold Silver Copper Iron Aluminum Compounds Ethanol Water Materials Glass Pyrex Granite Sand 0 128 0 128 0 235 0 385 0 449 0 903 2 42 4 18 0 75 0 79 0 84 5

Consider the reaction 2N2 g O 9 2N O g Using standard thermodynamic data at 298K calculate the free energy change when 1 840 moles of N g react at standard conditions AG rxn kJ Consider the reaction 2H O 1 2H g O g Using standard thermodynamic data at 298K calculate the free energy change when 2 11 moles of H 0 1 react at standard conditions AG rn k

In each he fills a reaction vessel with some mixture of the reactants and products at a constant temperature of 40 0 C and constant total pressure The he measures the reaction enthalpy AH and reaction entropy AS of the first reaction and the reaction enthalpy AH and reaction free energy AG of the second reaction The results of his measurements are shown in the table Complete the table That is calculate AG for the first reaction and AS for the second Round your answer to zero decimal places Then decide whether under the conditions the engineer has set up the reaction is spontaneous the reverse reaction is spontaneous or neither forward nor reverse reaction is spontaneous because the system is at equilibrium AL O3 s 3H g 2Al s 3H O g MgCl s H O 1 MgO s 2HCl g AH 951 kJ AS 3037 AG kJ Which is spontaneous this reaction the reverse reaction J K Oneither AH 140 kJ J 0x K AS AG 23 kJ Which is spontaneous this reaction erre reaction X

Teach system listed in the first column of the table below decide if possible whether the change described in the second column will increase the entropy S the system decrease S or leave S unchanged If you don t have enough information to decide check the not enough information button in the last column System A few grams of acetone vapor CH3 2CO A few moles of carbon dioxide CO gas A few moles of helium He gas Change The acetone condenses to a liquid at a constant temperature of 3 0 C The carbon dioxide is cooled from 26 0 C to 0 0 C and is also expanded from a volume of 5 0 L to a volume of 13 0 L The helium expands from a volume of 10 0 L to a volume of 11 0 L while the temperature is held constant at 59 0 C AS OAS 0 AS 0 AS 0 not enough information AS 0 AS 0 AS 0 not enough information AS 0 AS 0 AS 0 not enough information C

How many kilocalories are lost when 672 1 grams of water cools from 83 96 Celsius to 31 38 Celsius Hint The answer choice maybe either positive or negative depending on if energy is absorbed or released O a 30 94 kcal O b 35 34 kcal O c 55 34 kcal O d 65 44 kcal O e 37 14 kcal

If one gram of aluminum heats up faster than on gram of copper so the aluminum has a higher heat capacity True or False True False

How much heat is required to raise the temperature of 1 ml water by 20 C a 200 calories b 20 calories c 20 Calories d 20 Joules

What is the equation we use to determine the heat of reaction a F ma b E mc2 c q MCAT dT g m T

What are two of the factors that can change temperature a Heat and Mass of the material b Heat and the volume of the material c Heat and number of atoms d Mass and Volume of the material

What is the heat capacity of a substance a The inability of a material to change its temperature when heated b The ability of a material to change its temperature when heated c The inability of a material to move d The inability of a material to get heated

What is the relation between mass and temperature change a As mass is increased Temperature will increase with heat added b As mass in increased Temperature will stay the same when heated c There is no relation d As mass is increased Temperature will decrease with heat added

What is a definition of Temperature a The amount of heat in matter b The amount of heat in matter per volume heat density of that matter c Movement of molecules and atoms and their interactions with the univ d The hotness of something

What is internal energy a It is the amount of energy both kinetic and potential inside a molecule or ator that we can t directly measure b It is the potential energy inside a molecule or atom c It is the kinetic energy inside a molecule or atom d It is the heat inside a molecule or atom

1 Find AHfusion AHfusion Water Find negative q and this will equal AHfusion q mCAT or mwater CwaterATwater Cwater 1 calorie g C You have mass of the water and the ATwater from above results Ju multiply mass of water x 1 x Achange in temperature of the water multi negative one and this is your q which is also the AHfusion Your units will be calories

Calculate the amount of heat in Joules needed to raise 34 0g of water from 55 0 C to 76 0 C The specific heat of water is 4 18 J g C Show all work to receive full credit

5 As an alternative to combustion of coal gas described earlier in this section coal gas can undergo a process called methanation 3 H g CO g CH4 H O Determine the enthalpy change involved in the reaction of 300 g of carbon monoxide in this methanation reaction using the following reference equations and enthalpy changes 1 2 H2 g O2 g 2H O g 2 CO g 2 2 C 02 g 3 CHA 202 g 4 C O CO2 g 2 H O AH CO 0 AH 483 6 kJ AH 221 0 kJ AH AH 802 7 kJ 393 5 kJ

A chemist measures the energy change A during the following reaction 2H O 2H 0 0 9 AH 572 kj Use the information to answer the following question Suppose 13 3 g of H O react Calculate how much heat will be released or absorbed Be sure your answer has the correct number of significant digits kJ 0 8

A student placed a piece of nickel in a silver nitrate solution AgNO for a little while before removing it The student observed that silver metal Ag precipitated She isolated and massed the silver that was produced Due to her vast knowledge of chemistry the student predicted that nickel II nitrate Ni NO3 was also produced as described in the following chemical equation 2AgNO3 aq Ni s The student collected the following data Mass of beaker Mass of nickel before Mass of nickel after Mass of beaker with silver b 0 006 mol Ni c 0 08 mol Ni d 0 09 mol Ni Ni NO3 2 aq 106 28 g 5 00 g 4 65 g 107 56 g 17 Determine the mass in grams of Nickel that reacted and convert that mass to moles of Ni Be sure to note that the 5 00g of Ni was the amount that was added to the reaction and that the 4 65g of Ni was the amount of nickel that was left unreacted meaning that it was not part of the reaction LT 7 3 a 0 64 mol Ni c 17 1g Ag d 18 4g Ag I 18 Use your answer from 17 to predict the mass of silver Ag produced LT 7 5 a 0 64g Ag b 1 29g Ag 2Ag s 19 Determine the actual mass in grams of silver produced based on the data above a 0 35g Ag b 1 28g Ag c 102 56g Ag

Result report of a student group is shown in table Item value Wt of calorimeter Wt of calorimeter room temp water Wt of calorimeter warm water Temp of hot water Temp of room temp water Temp of warm water Specific heat of water 130 10 155 20 175 56 80 0 30 0 43 5 1 unit LO LO 9 LO 8 Cal g C How much weight of hot water two decimal answer How much heat of water at room temp two decimal answer How much heat of hot water two decimal answer How much heat of a calorimeter two decimal answer g calory calory How much heat capacity of the calorimeter two decimal answer calory cal

combustion of fuel to move a system of gears that move its wheels Not all of the fuel s energy is transferred to the wheels Which two options describe what happens to the rest of the energy A Some energy is lost because of the heat produced by the engine B Some energy is lost because of the weight of the car C Some energy is lost because of friction in the car s moving parts D Some energy is lost because it is transformed into chemical energy E Some energy is lost because it is transformed into potential energy

C6H12O6 6026CO 6H O AH 2803 kJ Using the information above determine the molar heat of combustion for one mole of water A 2803 kJ mole B 467 kJ mole 16 818 kl mole

A solid at absolute zero has no entropy because Select the correct answer below O the particles have no kinetic energy the particles exist in just one microstate the particles have no thermal energy O all of the above

To a calorimeter containing 300 0 g of water at 20 00 C 110 65 g of NaOH also at 20 00 C was added The temperature of the solution increased to 28 50 C If the specific heat of the mixture is 4 184 J g 1 C 1 and the small heat capacity of the calorimeter is ignored what is the heat evolved per mole of sodium hydroxide 153 kJ 37 4 kJ 41 5 kJ 90 5 kJ

Two students are trying to figure out the Calories per gram of potato chips They burn part of the potato chip and feel the heat They decide to measure this heat by putting a can of water above the burning potato chip so they can measure the heat gained by the water They collect the following data mass of potato chip before buming mass of potato chip after burning mass of water in can initial temperature of water final temperature of water 0 45 g 0 42 g 50 0 g 21 0 C 24 0 C 1 Calorie 1 000 calories specific heat of water 1 calorie g C What assumption was made by their calculation and what is the Cal g Hint the Cheeto Lab used the same multistep calculations The heat from the burning food all goes into the water air and can 5 0 Cal g The heat from the burning food all goes into the water air and can 0 36 Cal g The heat from the burning food all goes into the water 5 0 Cal g The heat from the burning food all goes into the water 0 36 Cal g

Q mxcx change in temperature 100 ml of 4 0 C water is heated until its temperature is 37 C If the specific heat of water is 4 18 J g C calculate how much heat you had to have added 100 J O 8 412 J O 10 320 J O 13 794 J

11 Is the mixing of different types of molecules in an ideal gas spontaneous Justify your answer using mathematical expressions for the chemical potential

For the reaction 2 Cu 0 s O g 4 CuO s calculate AG in kJ at 500 K 139 1 O 181 6 386 6 O 226 2 O 284 1 Ag s AgBr s AgCl s AgI s AgNO s Agz0 s Al s Als03 s Ba s CHC1 CH g C H g C H4 g C He g C He g 1675 7 0 0509 1582 3 0 0 0 0628 0 0 BaCl2 s 858 6 0 1237 810 4 1216 3 0 1121 1137 6 BaCO s BaO s 553 5 0 0704 525 1 BaSO4 s 1473 2 0 1322 1362 3 Brz 0 0 1522 0 0 C s 0 0057 0 0 CC1 f 135 4 0 2164 65 3 134 5 0 2017 73 7 74 8 0 1862 50 7 226 7 0 2008 217 1 52 3 0 2195 68 1 84 7 0 2295 32 9 103 8 0 2699 23 5 238 7 0 1268 166 3 277 7 0 1607 174 9 137 2 394 4 110 5 0 1976 393 5 0 2136 CH OH C H OH S AH kJ mol kJ K mol Co g CO g AG kJ mo1 at 25 C 0 0 0 0426 100 4 0 1071 127 1 0 0962 0 0 96 9 109 8 66 2 61 8 0 1155 124 4 0 1409 33 4 31 0 0 1213 11 2 0 0 0 0283 0 0 0 0 0 0 CaCO s CaD s Ca OH 2 8 CaSO4 s Cd s CdC1 s Cl g Cr s Cr O3 8 Cu s CuO s Cu 0 s Cus s Cu S s CuSO4 s F2 g Fe s Fe OH s Fe2O3 5 F 30 8 H g HBr g HC1 g HF g HI g HNO3 0 S AH kJ mol kJ K mol 1206 9 0 0929 1128 8 604 0 635 1 0 0398 986 1 0 0834 898 5 0 1067 1321 8 1434 1 0 0 391 5 0 1153 0 0518 0 0 0 2230 0 0 0 0238 1139 7 0 0812 1058 1 0 0 0 0332 0 0 157 3 0 0426 129 7 168 6 0 0931 146 0 53 1 0 0665 79 5 0 1209 771 4 0 1076 0 0 0 2027 0 0273 0 0 823 0 0 1067 696 6 824 2 0 0874 742 2 1118 4 0 1464 1015 5 0 0 0 1306 36 4 0 1986 92 3 0 1868 271 1 0 1737 26 5 0 2065 174 1 0 1556 AG kJ mol at 25 C 0 0 344 0 0 0 0 0 53 6 86 2 661 9 0 0 0 0 0 0 53 4 95 3 273 2 1 7 80 8

A solid sample of sodium carbonate Na CO3 s is placed in a test tube containing a solution of ethanoic acid CH COOH aq A gas is produced when the substances are mixed and the temperature of the test tube is observed to decrease AS for this reaction is Why Quest Ozone The moles of gas increase The moles of gas decrease The mass of product increases The mass of reactant decreases UV radiation in our atmosphere Upon absorption of

The solutions all originally at 20 0 C are combined in an insulated calorimeter The temperature of the reaction mixture is monitored as shown in the graph below ii Temperature C 34 0 32 0 30 0 28 0 26 0 24 0 22 0 20 0 18 0 d According to the graph what is the temperature change of the reaction mixture e The mass of the reaction mixture inside the calorimeter is 15 21 g i Calculate the magniture of the heat energy in joules that is released during the reaciton Assume that the specific heat of the reaction mixture is 3 94 J g C and that the heat absorbed by the calorimeter is negligible Time 00 2 Using the balance equation for the oxidation reduction reaction and your answer to part c calculate the value of the enthalpy change of the reaction AH xn in kJ molrxn Include the appropriate algebraic sign with your answer

Question 15 The melting and boiling points of substances can lead to inferences about the intermolecular attraction of the atoms of these substances because higher melting and boiling points indicate that the substances produce exothermic reactions A B C D the atomic mass of the substances is smaller atomic radii increase as heat is added more energy is needed to separate molecules

Reaction 1 4 NH3 g 502 g 4 NO g 6 H O AG 1010 kJ molrxn Reaction 2 2 NO2 g 2 NO g O2 g AG 70 kJ molrxn Reaction 3 4 NO2 g O2 g 2 H O 4 HNO3 aq AG 170 kJ molxn Based on the values of AG for the three reactions represented above what is the value of AG for the reaction represented below 4 NH3 g 8 02 g 4 HNO3 aq 4H O A A B 1040 kJ molxn 1110 kJ molrxn 1250 kJ molrxn 1320 kJ molrxn

Which of the following metal will have the greatest change in temperature Lithium 3 56 J g C O Magnesium 1 02 J g C Aluminum 0 900 J g C Potassium 0 750 J g C

Given the chart of bond energies calculate the enthalpy change for the reaction below Show all work to receive full credit Average Bond Energies kJ mol 413 kJ mol 348 kJ mol 293 kJ mol H H H CI H F N H N O 0 H 0 0 F F 436 kJ mol 431 kJ mol 567 kJ mol 391 kJ mol 201 kJ mol 463 kJ mol 146 kJ mol 155 kJ mol NEN C H C C C N C 0 C F C C C S CI CI 358 kJ mol 485 kJ mol 328 kJ mol 259 kJ mol 242 kJ mol H H H H H H C C CHN N N N N C N 614 kJ mol 839 kJ mol 799 kJ mol 495 kJ mol 1072 kJ mol 615 kJ mol 418 kJ mol 941 kJ mol 891 kJ mol H N H H H N H

An object that has a mass of 75 g is heated from 50 C to 93 C If it takes 3000 J for the temperature change to occur then what is the specific heat of the object

A B Ball C Which of these balloons would have the fastest moving particles if the pressure is the same in all 3

Of the following which is a process that increases entropy Select the correct answer below O CaO s CO2 g O H O 1 H O g CaCO3 s NH3 g HCl g NH4Cl s O P4 g 502 g P4010 s

Question 1 In the calorimetry experiment one student dissolved 10 21 g of CaCl to 100 g of water and watched the water temperature increased from 21 0 C to 34 5 C If the heat capacity of the calorimeter is 40 1 J C i ii 15 pts What is the enthalpy mol of the solution in the unit of kJ mol 5pts Is this dissolving process endothermic or exothermic the

14 2 points The quantity of heat of a body of matter absorbs or releases when it experiences a temperature change of 1 kelvin is the heat capacity of the body of matter True False

For which process is AS 0 Select the correct answer below O N g N aq O N g at 200KN g at 500K O Pb s Br 1 PbBr s 2 NO g N 04 g

15 2 points The value of a state function depends on the path of a process approaching to a specific state True False

7 2 points A standard enthalpy of formation is an enthalpy change for a reaction in which exactly 1 mole of a pure substance is formed from free elements in their most stable states un standard state conditions OO True False

5 points If the volume of a system decreases from 16 0 L to 10 7 L against a constant external pressure of 1 349 atm and releases 375 3 J of heat what is the change in internal energy i J of the system AEsys Given 1 L atm 101 3 J Answer to 1 decimal place Type your answer

For an exothermic process thermal energy is transferred from the surrounding to the system True False