Energetics Questions and Answers

D The three step mechanism for the following reaction can be seen below Z 2Q R L D Step 1 R QL M Step 2 M Z F Step 3 F Q D Fast Slow Fast a Deduce a rate expression for this reaction Hint Your rate expression can t conta intermediate remember that Rate Rate so you can use that to solve for the inter concentration etc

Give an example of the second law of thermodynamics

E Calculate the number of ions when one mole of the product is dissolved in water

Mercury is the only metal that is a liquid at room temperature When mercury vapor is inhaled it is readily absorbed by the lungs causing signifiant health risks The enthalpy of vaporization of mercury is 59 1 kJ mol The normal boiling point of mercury is 357 C What is the vapor pressure of mercury at 47 C Assume the enthalpy of vaporization does not depend on temperature Enter your answer to two significant figures Vapor pressure torr

An aqueous antifreeze solution is 20 0 ethylene glycol C H6O by mass The density of the solution is 1 05 g cm Calculate the molality molarity and mole fraction ethylene glycol Molality Molarity Mole fraction mol kg mol L

THERE 24 SEFE Cand WAYS GIGL NE PASA Kime World Studies Global Issues and Assessments N N Publishing 1995 adapted from NYS Global History and Geography Regents Exam August 2005 Directions 1 25 For each statement or question record on your separate ans sheet the number of the word or expression that of those given best complete the statement or answers the question Review later 18 These illustrations suggest that early Latin American civilizations 1 were based on European societies 2 used advanced technology to build complex structures 3 incorporated early Roman architectural design 4 were strongly influenced by Renaissance humanism Review later 19 Which of the following geographic challenges did the Aztec civilization face 1 Building structures that could survive hurricanes 2 Controlling a river that regularly flooded 3 A lack of farmland near their capital city

What is the value of the equilibrium constant K for the given reaction Express the answer in terms of log K 4XY 3Z 2Z3X 2Y Substance XY 1135 kJ mol 51 91 kJ mol Y 2 Z X 1081 93 kJ mol 9 1 kJ mol 1135 kJ mol AH mol 139 0 82 0 25 0 245 0 s J mol K 73 0 37 0 78 0 137 0

Solve the following problems using dimensional analysis Remember to label the units in every conversion factor include the appropriate units in your final answer and round for significant figures Work must be shown for full credit 1 Convert 950 centimeters into kilometers 2 Convert 0 10 cm to mm 3 Children s Motrin usually has 20 mg Ibuprofen per mL How many mg Ibuprofen are in 1 0 tablespoon 1 Tbsp 15 mL 4 How many hours are in a week

The normal boiling point of acetone an important laboratory and industrial solvent is 56 2 C and its AHVAP is 25 5 kJ mol At what temperature in C does acetone have a vapor pressure of 375 torr

meters molar heat capacity heat Label each variable in the given calorimetry equations with the property it represents charge mass change in time specific heat capacity change in temperature Avogadro s number number of moles q cxmx AT q Cxnx AT m

Green plants use light from the Sun to drive photosynthesis Photosynthesis is a chemical reaction in which water H O and carbon dioxide CO chemically react to form the simple sugar glucose C6H 2O6 and oxygen gas O What mass of water is consumed by the reaction of 8 99 g of carbon dioxide Round your answer to 3 significant digits

For the reversible one step reaction A A B C and the rate constant for the reverse reaction k is the rate constant for the forward reaction k is 281 L mol min 387 L mol min at a given temperature The activation energy for the forward reaction is 41 2 kJ mol whereas the activation energy for the reverse reaction is 23 4 kJ mol Determine the equilibrium constant K of this reaction K Determine whether this reaction is endothermic or exothermic endothermic O exothermic What effect will raising the temperature of the reaction have on the rate constants and the equilibrium constant Raising the temperature will increase the forward rate constant k more than it will increase the reverse rate constant k 1 resulting in an increase in the equilibrium constant K O Raising the temperature will increase the reverse rate constant k1 more than it will increase the forward rate constant k resulting in a decrease in the equilibrium constant K Raising the temperature will not affect either rate constant or the equilibrium constant K Raising the temperature will increase the forward rate constant k and reverse rate constant k1 equally leaving the equilibrium constant K unchanged

2 Cyclopropane isomerizes exothermically to propene as shown H 4 0 H C C H 1 I A 308 kJ mol C 423 kJ mol CIH H HIC C H H H AH 32 kJ mol 1 1 H H cyclopropane propene The C C single bond in propene has an estimated bond dissociation enthalpy BDE of 345 kJ mol while the C C double bond in propene has a BDE of 611 kJ mol Assuming that the C H bonds in propene and cyclopropane all have the same BDE what is the estimated BDE of a C C single bond in cyclopropane B 329 kJ mol 1 D 924 kJ mol

21 Which of the following equations correctly describe the change in internal energy AE of a reaction taking place in a bomb calorimeter I II AE q AE AH VAP A I only C Both I and II B II only D Neither I nor II

26 Calculate AG using the Gibbs Free Energy equation at standard temperature State whether or not the reactic will be spontaneous AH 638 4 kJ AS 156 9 J H CH3OH 1 5 02 CO2 2 H O

7 The frequency of blue light is 6 67 x1014 Hz How much energy does a photon of blue light carry h 6 626 x 10 34 J s 1 eV 1 60 x 10 19 1 56 eV 4 42 eV 2 76 eV

24 How much heat is transferred when 75 g of iron C 0 45 J g C is heated from 30 C to 650 C

The next three problems are linked together You will need this conversion 1 cal 4 18 J P 750 kg of iron are cooled from 100 C down to 25 C cp 4 6 x 10 J g C What amount of heat in calories and Joules was lost by the iron Answer q 6 2 X 106 cal 2 6 X 107 J The iron in the previous problem was cooled by submerging it in water at 10 C How much heat in calories and Joules was absorbed by the water Answer q 6 2 X 106 cal 2 6 X 107 J If the specific heat of water is 4 18 J g C how much water in kilograms at 10 C was required to cool down the iron wor 112 Izg

What is the energy input needed to heat 100 g frozen ethanol from 150 C to 110 C try looking up ethyl alcohol if you can t find the information for ethanol

Isopropanol C3H8O has a heat of of energy will be absorbed by 271 mL of isopropanol in order to evaporate at that temperature d 0 790 g mL vaporization of 45 4 kJ mol at 25 0 C How many joules 464 00

4 When the sun is high in the sky it delivers approximately 1000 watts of power to each square meter of the earth s surface The temperature of the surface of the sun is about 6000 K while that of the earth is about 300 K Estimate the entropy created in one year by the flow of solar heat onto a square meter of the earth Assume an average of 8 hours of sunlight per day

Calculate the amount of heat energy that must be added to change 23 5 g ice at 15 C to liquid water at 45 C

1 Write the thermochemical equation for the formation of calcium sulphate under standar conditions ii Calculate enthalpy of reaction for the given chemical equation CaSO4 s Na2CO3 s CaCO3 s Na2SO4 s AHof CaSO4 s 501 kJ mol AHo f Na2CO3 s 1130 7 kJ mol AHof CaCO3 s 1206 9 kJ mol AHof Na2SO4 s 1387 1 kJ mol

19 A 16 0 g sample of iron was heated from 0 C to 35 0 C It absorbed 246 4 J of energy as heat 20 Carbon tetrachloride was commonly used as an organic solvent until it was found to be carcinogenic How much heat is required to raise the temperature of 10 35 g of CCl4 from 32 1 C to 56 4 C The specific heat of CCl4 is 0 85651 J g C A B C D What is the specific heat of this piece of iron A 240 J g C B 3 67 J g C C 1 34 J g C D 0 44 J g C A 21 The specific heat of aluminum is 0 90 J g x C How much heat energy is required to raise the temperature from 20 C to 55 C of 11 0 grams of aluminum B C 206 J 218 J 193 J 215 J 82 8 J 347 J 428 J 7621

11 08 g of liquid methanol CH3OH is burned in excess oxygen gas according to the following Type numbers in the boxes reaction 6 points 2 CH OH 1 3 O g 2 CO g 4H O 1 The reaction releases 251 kJ of heat What is the AH for the reaction as written kJ mol

A 12 7 joules Specific Heat of Some Metals Iron 12 700 joules 35 4 joules 35 400 joules Aluminum Metal Copper Silver Lead Gold Specific Heat Capacity J gek 0 900 0 444 0 385 0 240 0 160 Refer to the table above A student wants to fry an egg in a 1 77 kg iron skillet An egg will become firm at 70 C 0 129 If the skillet begins at room temperature of 25 C what is the minimum amount of energy that must be transferred to the skillet in order to fry the egg

Bonus up to 1 pt At 1 atm how much energy is required to heat 69 0g H O s at 14 0 C to H O g at 157 0 C Hint Use heat transfer constants in Useful Information Edit Format Table

How much energy is absorbed when 129 g 2 propanol structure shown is vaporized at its normal boiling point of 82 3 C The AHvap of 2 propanol is 39 9 kJ mol at 82 3 C and its structure is shown here HHH H C C C H H O H H 2 Propanol O 5 150 kJ O 5 15 10 kJ O 85 6 kJ 1 04 kJ 85 649 kJ mol

If the specific heat of water is 4 18 J g C how much water in kilograms at 10 C was required to cool down the iron

10 NH4NO3 decomposes to make nitrogen gas oxygen gas and water 2 pts Write a balanced equation for the reaction 8 pts How many L of nitrogen gas at 1 2 atm and 125 C are produced from the decomposition of 25 g of NH4NO3

15 Board A cylinder is filled with argon gas It has a diameter of 14m and a height of 20m It is stored at 45C and at 600N pressure The container is then pressurized at 90kPa and the temperature is adjusted to 250K What is the adjusted volume of the gas 1 Point O 2278 m 3 4000 m 3 1353 m 3

A cool Bunsen burner flame is used to heat substances in a test tube because it will heat the substance better it will waiver in the air less than a hot flame all of these choices are valid it will be less likely to crack the test tube

SEP Using Mathematics Why does the sum of the two types of energy always have that pattern mentioned in the previous question O a Ob O c Od O e Because Chemical Energy is Added Together Because Energy is Always Conserved Because the Two Types Just Always have the Pattern for No Reason All the Above Are Correct None of the Above Are Correct

During the reaction below the bond energy is Select Select is Select Staying the Same Increasing N2 g O Decreasing Answer 1 Decreasing Answer 2 Endothermic v so the reaction H 180 6kJ mol

A person reacts 0 86mol of carbon with 38 22mol of hydrogen gas How much energy is released during the reaction Use a negative number if energy is released and a positive number if energy is added 4C s 5H g C4H10 g AH 125 6 kJ mol

To treat a burn on his hand a person decides to place an ice cube on the burned skin The mass of the ice cube is 11 9 g and its initial temperature is 12 4 C The water resulting from the melted ice reaches the temperature of his skin 29 6 C How much heat is absorbed by the ice cube and resulting water Assume that all of the water remains in the hand Constants for water can be found in this table

Learni Two 20 0 g ice cubes at 14 0 C are placed into 205 g of water at 25 0 C Assuming no energy is transferred to or from the surroundings calculate the final temperature Tf of the water after all the ice melts heat capacity of H O s heat capacity of H O 1 enthalpy of fusion of H O 37 7 J mol K 75 3 J mol K 6 01 kJ mol Tf

The vapor pressure P of a certain liquid was measured at two temperatures T The data is shown in the table T K P kPa 325 3 45 875 7 97 Keep the pressure units in kilopascals If you were going to graphically determine the enthalpy of vaporizaton AH vap avoid rounding errors use three significant figures in the x values and four significant figures in the y values for this liquid what points would you plot To point 1 x point 1 y

A certain substance has a heat of vaporization of 38 86 kJ mol At what Kelvin temperature will the vapor pressure be 5 00 times higher than it was at 341 K T K

How many grams of ethanol C H OH can be boiled with 378 4 kJ of heat energy The molar heat of vaporization of ethanol is 38 6 kJ mol mass of ethanol g

Which reaction results in an increase in the entropy of a system

54 2 points A precipitate forms when AgNO3 and HCl are combined Is this an endothermic or exothermic process Exothermic Endothermic Previous

50 2 points In the reaction NH4Cl s heat energy is released and entropy increases energy is absorbed and entropy decreases energy is absorbed and entropy increases energy is released and entropy decreases NH3 g HCl g

23 2 points In a spontaneous exothermic chemical reaction entropy may increase or decrease True False

Which of the following is the smallest quantity of energy O a 1 kilocalorie Ob 1 joule O c 1 calorie Od 1 kilojoule e All are the same amount of energy

J g C has a mass of 42 9 g is heated The mass of the liquid water is 31 6 g at an initial temperature of 25 1 C When the hot metal e of 55 7 C What is the temperature in Celsius C of the metal when it was heated specific heat of water is 4 184 J g C initial

According to the energy diagram below which value for the curve would change by the addition of a catalyst ENERGY DIAGRAM Energy O value c O value b O value d value a Reactants b c Course of the Reaction Products d

o pts An unknown metal with a specific heat of 0 790 J g C has a mass of 42 9 g is heated The mass of the liquid water is 31 6 g at an initial temperature of 25 1 C When the hot metal is placed into the water they reach a temperature of 55 7 C What is the initial temperature in Celsius C of the metal when it was heated specific heat of water is 4 184 J g C must show all the calculations

The plateau or flat line on either a heating or cooling curve represents a decrease in temperature O a change of state all states exist together a temperature change there exist no plateau line Question 20

Calculate the heat in Joules needed to freeze 35 g of water at 0 C heat of fusion 80 cal g water 1 cal 4 184 J 12000 J O 360 J 7500 J O 510 J O 35 J